My family have a fair number of electrical devices ranging from mobile
phones to electronic games to fridges, all of which lend themselves to
being able to be powered or charged on the road by a 12V cigarette
lighter adapter.

My question is, how safe are these adapters in terms of risking possible
damage to the device in question?  I read about 'surges' in power from
the car; if so, is it down to circuitry built in to the device in
question to protect itself from that?  Or should such protection be
built into the actual adapter?

Is it risky to buy a 'cheapo' aftermarket adapter in place of the device
manufacturer - might that be a more dangerous proposition than buying an
'original' item?  If so, how can you tell what's safe, other than by
spending as much cash as possible?  Can an existing adapter be tested
for this?

Thanks
David

"Lobster"  wrote in message 
news:%Bnjk.87650$oo.47991@newsfe09.ams2...
> My family have a fair number of electrical devices ranging from mobile
> phones to electronic games to fridges, all of which lend themselves to
> being able to be powered or charged on the road by a 12V cigarette
> lighter adapter.
>
> My question is, how safe are these adapters in terms of risking possible
> damage to the device in question?

I've never had any problem with damage to delicate equipment like phones or 
satnav. Its a wise precaution to connect the ciggy plug before connecting 
the equipment just incase the power goes on and off a few times as you plug 
it in, but I've never had any problem.

> I read about 'surges' in power from
> the car; if so, is it down to circuitry built in to the device in
> question to protect itself from that?  Or should such protection be
> built into the actual adapter?

Varies. Some adaptor leads have a regulator inside to bring voltage down to 
what the equipment needs and this will give protection, but from what? 
Alternator going overvolts will be sunk into the battery, so impossible to 
go above the battery terminal voltage.

> Is it risky to buy a 'cheapo' aftermarket adapter in place of the device
> manufacturer - might that be a more dangerous proposition than buying an
> 'original' item?  If so, how can you tell what's safe, other than by
> spending as much cash as possible?  Can an existing adapter be tested
> for this?

I'm not concerned, but as you obviously are, then it would seem best to use 
the branded manufacturers lead, but I wouldn't bother myself as never had 
any problem. Just connect the ciggy plug first to prevent any problem with 
the power going on and off rapidly while the equipment is connected.

Graham

Graham wrote:
> "Lobster"  wrote in message 
> news:%Bnjk.87650$oo.47991@newsfe09.ams2...
>> My family have a fair number of electrical devices ranging from mobile
>> phones to electronic games to fridges, all of which lend themselves to
>> being able to be powered or charged on the road by a 12V cigarette
>> lighter adapter.
>>
>> My question is, how safe are these adapters in terms of risking possible
>> damage to the device in question?
> 
> I've never had any problem with damage to delicate equipment like phones or 
> satnav. Its a wise precaution to connect the ciggy plug before connecting 
> the equipment just incase the power goes on and off a few times as you plug 
> it in, but I've never had any problem.
> 
>> I read about 'surges' in power from
>> the car; if so, is it down to circuitry built in to the device in
>> question to protect itself from that?  Or should such protection be
>> built into the actual adapter?
> 
> Varies. Some adaptor leads have a regulator inside to bring voltage down to 
> what the equipment needs and this will give protection, but from what? 
> Alternator going overvolts will be sunk into the battery, so impossible to 
> go above the battery terminal voltage.
> 
>> Is it risky to buy a 'cheapo' aftermarket adapter in place of the device
>> manufacturer - might that be a more dangerous proposition than buying an
>> 'original' item?  If so, how can you tell what's safe, other than by
>> spending as much cash as possible?  Can an existing adapter be tested
>> for this?
> 
> I'm not concerned, but as you obviously are, then it would seem best to use 
> the branded manufacturers lead, but I wouldn't bother myself as never had 
> any problem. Just connect the ciggy plug first to prevent any problem with 
> the power going on and off rapidly while the equipment is connected.

Thanks for the response.  I'm not so much "concerned" as ignorant!  and 
seeking advice as to whether it's an issue or not.  I've certainly used 
quite a few adaptors myself for different deviced without problems, and 
other than *possibly* a camping fridge which expired under warranty 
under dubious circumstances.  I've recently bought a notebook computer 
which would be by far the most expensive device to charge from the car; 
hence the current interest.

David

On Jul 28, 9:50 pm, Lobster  wrote:
> Graham wrote:
> > "Lobster"  wrote in message
> >news:%Bnjk.87650$oo.47991@newsfe09.ams2...
> >> My family have a fair number of electrical devices ranging from mobile
> >> phones to electronic games to fridges, all of which lend themselves to
> >> being able to be powered or charged on the road by a 12V cigarette
> >> lighter adapter.
>
> >> My question is, how safe are these adapters in terms of risking possible
> >> damage to the device in question?
>
> > I've never had any problem with damage to delicate equipment like phones or
> > satnav. Its a wise precaution to connect the ciggy plug before connecting
> > the equipment just incase the power goes on and off a few times as you plug
> > it in, but I've never had any problem.
>
> >> I read about 'surges' in power from
> >> the car; if so, is it down to circuitry built in to the device in
> >> question to protect itself from that?  Or should such protection be
> >> built into the actual adapter?
>
> > Varies. Some adaptor leads have a regulator inside to bring voltage down to
> > what the equipment needs and this will give protection, but from what?
> > Alternator going overvolts will be sunk into the battery, so impossible to
> > go above the battery terminal voltage.
>
> >> Is it risky to buy a 'cheapo' aftermarket adapter in place of the device
> >> manufacturer - might that be a more dangerous proposition than buying an
> >> 'original' item?  If so, how can you tell what's safe, other than by
> >> spending as much cash as possible?  Can an existing adapter be tested
> >> for this?
>
> > I'm not concerned, but as you obviously are, then it would seem best to use
> > the branded manufacturers lead, but I wouldn't bother myself as never had
> > any problem. Just connect the ciggy plug first to prevent any problem with
> > the power going on and off rapidly while the equipment is connected.
>
> Thanks for the response.  I'm not so much "concerned" as ignorant!  and
> seeking advice as to whether it's an issue or not.  I've certainly used
> quite a few adaptors myself for different deviced without problems, and
> other than *possibly* a camping fridge which expired under warranty
> under dubious circumstances.  I've recently bought a notebook computer
> which would be by far the most expensive device to charge from the car;
> hence the current interest.
>
> David

Its certainly an issue, car electrics are very hostile in terms of
transients, and lots of appliances just dont survive them. FWIW if the
car is switched off the nasty transients dont happen, but thats a less
than reliable way to avoid the problem.

Consider the cost of incorporating protection into an adaptor, and
what youre paying for one. I'd be cautious before running anything not
bulletproof on car 12v, as for a laptop noooooo. If the appliance in
question comes with a car connector then its usually designed to
tolerate car supplies, but if not its a risky strategy.

If you want to run masses of appliances from the car, a small SLA with
a 2 way switch would solve the problem - the switch enables it to
connect to either car electrics or appliance, but never both. 12v SLAs
tolerate lower charge voltage than car batteries, so a series diode
would be wanted.

Nicads could also be used in pricniple, but there are then more
complex charging issues to deal with.


NT

wrote in message
news:4c452fcc-5a2d-4719-81ad-b1aac4855dc9@25g2000hsx.googlegroups.com...
On Jul 28, 9:50 pm, Lobster  wrote:


Its certainly an issue, car electrics are very hostile in terms of
transients, and lots of appliances just dont survive them. FWIW if the
car is switched off the nasty transients dont happen, but thats a less
than reliable way to avoid the problem.

Consider the cost of incorporating protection into an adaptor, and
what youre paying for one. I'd be cautious before running anything not
bulletproof on car 12v, as for a laptop noooooo. If the appliance in
question comes with a car connector then its usually designed to
tolerate car supplies, but if not its a risky strategy.

If you want to run masses of appliances from the car, a small SLA with
a 2 way switch would solve the problem - the switch enables it to
connect to either car electrics or appliance, but never both. 12v SLAs
tolerate lower charge voltage than car batteries, so a series diode
would be wanted.

Nicads could also be used in pricniple, but there are then more
complex charging issues to deal with.


>>> (why don't this indent previous message?)>>>

Total Bollocks.

As I'm not in a very good mood, I'll call it like Conor.

All complex equipment like a laptop has a very complex power supply.
Providing you have the 12v to laptop power supply provided by the laptop
manfacturer, it will be absolutely fine. My old Dell ran happily off the car
for years and that was with an after market 12 volt to laptop supply.

Graham

i think the biggest danger with 12volt devices
is of fire,
if a wire is too thin it can get hot 
and burn plastic -
it happened to me  with my car second battery charger-
i had a fuse on one battery but not on the second-
whooops

-- 

                   [george]

~

In article <%Bnjk.87650$oo.47991@newsfe09.ams2>,
   Lobster  wrote:
> My family have a fair number of electrical devices ranging from mobile
> phones to electronic games to fridges, all of which lend themselves to
> being able to be powered or charged on the road by a 12V cigarette
> lighter adapter.

> My question is, how safe are these adapters in terms of risking possible
> damage to the device in question?  I read about 'surges' in power from
> the car; if so, is it down to circuitry built in to the device in
> question to protect itself from that?  Or should such protection be
> built into the actual adapter?

I'm not quite sure how you'd get 'surges' in power in a car, given it has
an extremely low impedance vast capacitor sitting across the line - the
battery. And I'd also say anything fitted with a fag lighter plug is
designed to work with car electrics - it's not a standard used elsewhere.
So yes - most will have some form of regulation either in the plug or the
device itself, as phones and Tom Toms etc don't have 12 volt internal
batteries. 

> Is it risky to buy a 'cheapo' aftermarket adapter in place of the device
> manufacturer - might that be a more dangerous proposition than buying an
> 'original' item?  If so, how can you tell what's safe, other than by
> spending as much cash as possible?  Can an existing adapter be tested
> for this?

You mean a connecting lead for say a phone which isn't a genuine maker's
accessory? Could be anything. So I'd buy it from a reputable source. 

> Thanks
> David

-- 
*Is there another word for synonym?

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In article
,
    wrote:
> Its certainly an issue, car electrics are very hostile in terms of
> transients, and lots of appliances just dont survive them.

What, for example?  Most of the things you plug into a fag socket don't
actually run off 12 volts so will have voltage regulation somewhere -
either internal or in the lead. And a standard regulator will cope with
about 40 volts.
 Most cars these days are packed with electronics. They seem to survive
this 'hostile' environment ok.

-- 
*One of us is thinking about sex... OK, it's me.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

On Tue, 29 Jul 2008 00:27:12 +0100, Dave Plowman (News)  
 wrote:

> In article
> ,
>     wrote:
>> Its certainly an issue, car electrics are very hostile in terms of
>> transients, and lots of appliances just dont survive them.
>
> What, for example?  Most of the things you plug into a fag socket don't
> actually run off 12 volts so will have voltage regulation somewhere -
> either internal or in the lead. And a standard regulator will cope with
> about 40 volts.
>  Most cars these days are packed with electronics. They seem to survive
> this 'hostile' environment ok.
>


& if the batteries connected it provides rather good transient protection.

On Mon, 28 Jul 2008 23:50:29 +0100, Graham  wrote:

>  wrote in message
> news:4c452fcc-5a2d-4719-81ad-b1aac4855dc9@25g2000hsx.googlegroups.com...
> On Jul 28, 9:50 pm, Lobster  wrote:
>
>
> Its certainly an issue, car electrics are very hostile in terms of
> transients, and lots of appliances just dont survive them.

I've yet to destroy anything that plugs into a cigarette socket with them

> FWIW if the
> car is switched off the nasty transients dont happen, but thats a less
> than reliable way to avoid the problem.
>
> Consider the cost of incorporating protection into an adaptor, and
> what youre paying for one. I'd be cautious before running anything not
> bulletproof on car 12v, as for a laptop noooooo. If the appliance in
> question comes with a car connector then its usually designed to
> tolerate car supplies, but if not its a risky strategy.
>
> If you want to run masses of appliances from the car, a small SLA with
> a 2 way switch would solve the problem - the switch enables it to
> connect to either car electrics or appliance, but never both. 12v SLAs
> tolerate lower charge voltage than car batteries, so a series diode
> would be wanted.
>

Most car batteries need aloer charge voltage than SLAs.


> Nicads could also be used in pricniple, but there are then more
> complex charging issues to deal with.
>
>
>>>> (why don't this indent previous message?)>>>
>
> Total Bollocks.
>
> As I'm not in a very good mood, I'll call it like Conor.
>
> All complex equipment like a laptop has a very complex power supply.
> Providing you have the 12v to laptop power supply provided by the laptop
> manfacturer, it will be absolutely fine. My old Dell ran happily off the  
> car
> for years and that was with an after market 12 volt to laptop supply.
>
> Graham
>
>
>
>

Dave Plowman (News) wrote:

[...]
> 
> I'm not quite sure how you'd get 'surges' in power in a car, given it has
> an extremely low impedance vast capacitor sitting across the line - the
> battery.

Unless the battery terminal to cable connection is poor, of course!

;-)

Chris

-- 
Remove prejudice to reply.

On Tue, 29 Jul 2008 07:49:39 +0100, Chris Whelan  
 wrote:

> Dave Plowman (News) wrote:
>
> [...]
>>
>> I'm not quite sure how you'd get 'surges' in power in a car, given it  
>> has
>> an extremely low impedance vast capacitor sitting across the line - the
>> battery.
>
> Unless the battery terminal to cable connection is poor, of course!
>
> ;-)
>
> Chris
>


You'll have plenty of other things to worry about if that's happened :-)

"George (dicegeorge)"  wrote in message 
news:g6ljj4$nu$1@energise.enta.net...
>i think the biggest danger with 12volt devices
> is of fire,
> if a wire is too thin it can get hot and burn plastic -
> it happened to me  with my car second battery charger-
> i had a fuse on one battery but not on the second-
> whooops

That is why there should always be a fuse as close to the battery as 
possible. Close to battery so there is only the smallest length of wire 
unprotected from a short should the insulation chaff and touch the body. Its 
surprising how often long lengths are left completely unprotected or naively 
fused at the far end. By all means fuse at lower amperage at the far end, 
but there must always be a fuse at the battery end to blow if a short to the 
body along the cable run. These days cars have a fusible link next to the 
battery terminal, but this is designed to stop wiring catching fire and a 
very high current rating, so not to be relied on for protection. Pick up 
power after the fuse box or if for some reason its needed to connect 
directly to the battery, say because its a very powerful piece of equipment 
like an inverter or ridiculously powerful car audio system, then put a fuse 
within an inch or two of the battery.

Graham

Duncan Wood wrote:

> On Tue, 29 Jul 2008 07:49:39 +0100, Chris Whelan
>  wrote:
> 
>> Dave Plowman (News) wrote:
>>
>> [...]
>>>
>>> I'm not quite sure how you'd get 'surges' in power in a car, given it
>>> has
>>> an extremely low impedance vast capacitor sitting across the line - the
>>> battery.
>>
>> Unless the battery terminal to cable connection is poor, of course!
>>
>> ;-)
>>
>> Chris
>>
> 
> 
> You'll have plenty of other things to worry about if that's happened :-)

LOL!

Chris

-- 
Remove prejudice to reply.

In article <g6ljj4$nu$1@energise.enta.net>,
   George \(dicegeorge\)  wrote:
> i think the biggest danger with 12volt devices
> is of fire,
> if a wire is too thin it can get hot 
> and burn plastic -
> it happened to me  with my car second battery charger-
> i had a fuse on one battery but not on the second-
> whooops

Fag lighter adaptors have a fuse built in.

But simply don't use wire not up to the job in hand.

-- 
*Growing old is inevitable, growing up is optional

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In article <74zjk.53414$9I1.30823@newsfe16.ams2>,
   Chris Whelan  wrote:
> > I'm not quite sure how you'd get 'surges' in power in a car, given it
> > has an extremely low impedance vast capacitor sitting across the line
> > - the battery.

> Unless the battery terminal to cable connection is poor, of course!

> ;-)

Then no 'spikes' because the engine won't start. Unless you jump start it,
of course. Which seems a bit extreme just to use your mobile.

-- 
*I finally got my head together, now my body is falling apart.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Dave Plowman (News) wrote:

> In article <74zjk.53414$9I1.30823@newsfe16.ams2>,
>    Chris Whelan  wrote:
>> > I'm not quite sure how you'd get 'surges' in power in a car, given it
>> > has an extremely low impedance vast capacitor sitting across the line
>> > - the battery.
> 
>> Unless the battery terminal to cable connection is poor, of course!
> 
>> ;-)
> 
> Then no 'spikes' because the engine won't start. Unless you jump start it,
> of course. Which seems a bit extreme just to use your mobile.
> 

:-)

Chris

-- 
Remove prejudice to reply.

Graham wrote:

>> Varies. Some adaptor leads have a regulator inside to bring voltage down to 
>> what the equipment needs and this will give protection, but from what? 
>> Alternator going overvolts will be sunk into the battery, so impossible to 
>> go above the battery terminal voltage.

Utter and total bullshite.
-- 
Dave
GS850x2 XS650 SE6a

"It's a moron working with power tools.
 How much more suspenseful can you get?"
 - House

On Mon, 28 Jul 2008 18:46:34 +0100, Lobster 
wrote:

>My question is, how safe are these adapters in terms of risking possible
>damage to the device in question?  I read about 'surges' in power from
>the car; 

<snip>
AFAIK
The main source of surge/spike is when the starter motor stops turning - all
those amps used to create the magnetic field have to go somewhere fast...
On light aircraft, the rule is all avionics OFF until the engine has started.
I neglected to turn off one item once and was rewarded with a fascinating
display of random numbers/symbols (luckily no permanent damage)
Just checked my car - the radio and cigar lighter power is disconnected from the
supply while the engine is being started.
I think you would probably be ok but if in doubt, just pull the plug out until
engine running - this assumes you don't have any unusual heavy electrical items
connected e.g. motors, large solenoids etc.

Geo

On Jul 29, 12:27 am, "Dave Plowman (News)" 
wrote:
> In article
> ,
>     wrote:
>
> > Its certainly an issue, car electrics are very hostile in terms of
> > transients, and lots of appliances just dont survive them.
>
> What, for example?

Anything electronic that isnt specifically designed to run on car
systems. Also some things that are - cost cutting invertors for
example tend to lack the ability to survive all transients, hence wont
last forever.

>  Most of the things you plug into a fag socket don't
> actually run off 12 volts so will have voltage regulation somewhere -
> either internal or in the lead. And a standard regulator will cope with
> about 40 volts.

which isnt sufficient.

>  Most cars these days are packed with electronics. They seem to survive
> this 'hostile' environment ok.

Theyre designed to. They have input filters that can cope with _60v.

Cars have a high current inductive power source, the alternator, and
the battery isnt close enough to eliminate substantial high frequency
overvoltage transients in the event of load dump. This is fairly basic
electronics stuff, maybe the OP should ask in sci.electronics.basics.
Diy and electronics really are 2 different animals, and ukdiy is not
an electronics expert group.


NT

Geo wrote:
> On Mon, 28 Jul 2008 18:46:34 +0100, Lobster 
> wrote:
> 
>> My question is, how safe are these adapters in terms of risking possible
>> damage to the device in question?  I read about 'surges' in power from
>> the car; 
> 
> <snip>
> AFAIK
> The main source of surge/spike is when the starter motor stops turning - all
> those amps used to create the magnetic field have to go somewhere fast...
> On light aircraft, the rule is all avionics OFF until the engine has started.
> I neglected to turn off one item once and was rewarded with a fascinating
> display of random numbers/symbols (luckily no permanent damage)
> Just checked my car - the radio and cigar lighter power is disconnected from the
> supply while the engine is being started.
> I think you would probably be ok but if in doubt, just pull the plug out until
> engine running - this assumes you don't have any unusual heavy electrical items
> connected e.g. motors, large solenoids etc.
> 
> Geo

But would that apply if, for example, you were trying to restart the 
engine in flight?

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

On Tue, 29 Jul 2008 13:06:40 +0100, Rod  wrote:

>But would that apply if, for example, you were trying to restart the 
>engine in flight?
Yes - the only supply required from the battery is the starter motor - ignition
is from two independent magnetos (2 plugs per cylinder).

Geo

In article
,
    wrote:
> > > Its certainly an issue, car electrics are very hostile in terms of
> > > transients, and lots of appliances just dont survive them.
> >
> > What, for example?

> Anything electronic that isnt specifically designed to run on car
> systems.

Then it won't come with a fag lighter plug?

> Also some things that are - cost cutting invertors for
> example tend to lack the ability to survive all transients, hence wont
> last forever.

More likely damaged by overload. You'd be hard pressed to find mosfets
that can be damaged by the sort of voltage spikes found in a car.  

> >  Most of the things you plug into a fag socket don't
> > actually run off 12 volts so will have voltage regulation somewhere -
> > either internal or in the lead. And a standard regulator will cope with
> > about 40 volts.

> which isnt sufficient.

Then every other piece of electronics will die too. Have you never built
any car electronics - or is this some theory plucked from the air?   

> >  Most cars these days are packed with electronics. They seem to survive
> > this 'hostile' environment ok.

> Theyre designed to. They have input filters that can cope with +_60v.

Ah so now we have a figure. Can I ask where the 60 volts comes from?  

> Cars have a high current inductive power source, the alternator, and
> the battery isnt close enough to eliminate substantial high frequency
> overvoltage transients in the event of load dump. This is fairly basic
> electronics stuff, maybe the OP should ask in sci.electronics.basics.
> Diy and electronics really are 2 different animals, and ukdiy is not
> an electronics expert group.

There's lots of these theories doing the rounds that simply don't happen
in practice. And yes, I have looked at several car systems with a 'scope.  
Of course you get rubbish on it otherwise there's be no need to filter
amplifier supplies etc - but those spikes ain't capable of doing damage.

-- 
*I didn't fight my way to the top of the food chain to be a vegetarian.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Geo wrote:
> On Tue, 29 Jul 2008 13:06:40 +0100, Rod  wrote:
> 
>> But would that apply if, for example, you were trying to restart the 
>> engine in flight?
> Yes - the only supply required from the battery is the starter motor - ignition
> is from two independent magnetos (2 plugs per cylinder).
> 
> Geo

I meant, would it be OK to turn off all avionics while struggling to get 
the engine running again. I imagine that would include altimeter, radio, 
etc.?

I know nothing about aircraft but am thinking that the systems will be 
broadly similar to cars - when the engine is not running, all ancillary 
equipment will run off battery?

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

On Tue, 29 Jul 2008 13:43:18 +0100, Rod  wrote:

>I meant, would it be OK to turn off all avionics while struggling to get 
>the engine running again. I imagine that would include altimeter, radio, 
>etc.?

Yes - I am talking small (say 4 seat) aircraft in good weather.
The aircraft will fly with basic instruments without battery power.
Altimeter, airspeed and compass.
Generally only two flight instruments are battery powered (in common
Cessnas/Pipers) the direction indicator gyro and the turn/slip indicator.
The other (avionics)stuff is mostly for flying when you can't see anything out
of the window.
>I know nothing about aircraft but am thinking that the systems will be 
>broadly similar to cars - when the engine is not running, all ancillary 
>equipment will run off battery?
That is correct - in the event of alternator failure (for example) all
unecessary stuff is switched off to conserve battery power for a couple of radio
calls before landing at the nearest airfield.

Geo

On Tue, 29 Jul 2008 13:20:43 +0100, Dave Plowman (News)  
 wrote:

> In article
> ,
>     wrote:
>> > > Its certainly an issue, car electrics are very hostile in terms of
>> > > transients, and lots of appliances just dont survive them.
>> >
>> > What, for example?
>
>> Anything electronic that isnt specifically designed to run on car
>> systems.
>
> Then it won't come with a fag lighter plug?
>
>> Also some things that are - cost cutting invertors for
>> example tend to lack the ability to survive all transients, hence wont
>> last forever.
>
> More likely damaged by overload. You'd be hard pressed to find mosfets
> that can be damaged by the sort of voltage spikes found in a car.
>
>> >  Most of the things you plug into a fag socket don't
>> > actually run off 12 volts so will have voltage regulation somewhere -
>> > either internal or in the lead. And a standard regulator will cope  
>> with
>> > about 40 volts.
>
>> which isnt sufficient.
>
> Then every other piece of electronics will die too. Have you never built
> any car electronics - or is this some theory plucked from the air?
>
>> >  Most cars these days are packed with electronics. They seem to  
>> survive
>> > this 'hostile' environment ok.
>
>> Theyre designed to. They have input filters that can cope with +_60v.
>
> Ah so now we have a figure. Can I ask where the 60 volts comes from?
>

Last time looked it was 55V (TI automotive spec for semiconducters)




>> Cars have a high current inductive power source, the alternator, and
>> the battery isnt close enough to eliminate substantial high frequency
>> overvoltage transients in the event of load dump. This is fairly basic
>> electronics stuff, maybe the OP should ask in sci.electronics.basics.
>> Diy and electronics really are 2 different animals, and ukdiy is not
>> an electronics expert group.
>
> There's lots of these theories doing the rounds that simply don't happen
> in practice. And yes, I have looked at several car systems with a 'scope.
> Of course you get rubbish on it otherwise there's be no need to filter
> amplifier supplies etc - but those spikes ain't capable of doing damage.
>

Well the installed stuff's normally designed to cope with far worse  
situations than you normally ever see. But if you're worried a couple of  
16V Zeners or VDRs are hardly expensive.

On Tue, 29 Jul 2008 12:39:44 +0100, Geo  wrote:

> On Mon, 28 Jul 2008 18:46:34 +0100, Lobster  
> 
> wrote:
>
>> My question is, how safe are these adapters in terms of risking possible
>> damage to the device in question?  I read about 'surges' in power from
>> the car;
>
> <snip>
> AFAIK
> The main source of surge/spike is when the starter motor stops turning -  
> all
> those amps used to create the magnetic field have to go somewhere fast...


Across the switch contacts unless you've wired it oddly.

> On light aircraft, the rule is all avionics OFF until the engine has  
> started.
> I neglected to turn off one item once and was rewarded with a fascinating
> display of random numbers/symbols (luckily no permanent damage)
> Just checked my car - the radio and cigar lighter power is disconnected  
> from the
> supply while the engine is being started.

That's to maximise the available current though :-)


> I think you would probably be ok but if in doubt, just pull the plug out  
> until
> engine running - this assumes you don't have any unusual heavy  
> electrical items
> connected e.g. motors, large solenoids etc.
>
> Geo

On 29 Jul, 14:36, "Duncan Wood"  wrote:
> On Tue, 29 Jul 2008 12:39:44 퍝, Geo  wrote> > On Mon, 28 Jul 2008 18:46:34 퍝, Lobster  
> > 
> > wrote:
>
> >> My question is, how safe are these adapters in terms of risking possible
> >> damage to the device in question?  I read about 'surges' in power from
> >> the car;
>
> > <snip>
> > AFAIK
> > The main source of surge/spike is when the starter motor stops turning -  
> > all
> > those amps used to create the magnetic field have to go somewhere fast.> Across the switch contacts unless you've wired it oddly.
>
> > On light aircraft, the rule is all avionics OFF until the engine has  
> > started.
> > I neglected to turn off one item once and was rewarded with a fascinating
> > display of random numbers/symbols (luckily no permanent damage)
> > Just checked my car - the radio and cigar lighter power is disconnected  
> > from the
> > supply while the engine is being started.
>
My past satnav had definite instruction that not to plug in, until car
started.
My current Tom Tom has no such request.

> That's to maximise the available current though :-)
>
>
>
> > I think you would probably be ok but if in doubt, just pull the plug out  
> > until
> > engine running - this assumes you don't have any unusual heavy  
> > electrical items
> > connected e.g. motors, large solenoids etc.
>
> > Geo- Hide quoted text -
>
> - Show quoted text -

On 29 Jul, 17:42, Gel  wrote:
> On 29 Jul, 14:36, "Duncan Wood"  wrote:
>
> > On Tue, 29 Jul 2008 12:39:44 퍝, Geo  wrote:
> > > On Mon, 28 Jul 2008 18:46:34 퍝, Lobster  
> > > 
> > > wrote:
>
> > >> My question is, how safe are these adapters in terms of risking possible
> > >> damage to the device in question?  I read about 'surges' in power from
> > >> the car;
>
> > > <snip>
> > > AFAIK
> > > The main source of surge/spike is when the starter motor stops turning -  
> > > all
> > > those amps used to create the magnetic field have to go somewhere fast...
>
> > Across the switch contacts unless you've wired it oddly.
>
> > > On light aircraft, the rule is all avionics OFF until the engine has  
> > > started.
> > > I neglected to turn off one item once and was rewarded with a fascinating
> > > display of random numbers/symbols (luckily no permanent damage)
> > > Just checked my car - the radio and cigar lighter power is disconnected  
> > > from the
> > > supply while the engine is being started.
>
> My past satnav had definite instruction that not to plug in, until car
> started.
> My current Tom Tom has no such request.
>
> > That's to maximise the available current though :-)
>
> > > I think you would probably be ok but if in doubt, just pull the plug out  
> > > until
> > > engine running - this assumes you don't have any unusual heavy  
> > > electrical items
> > > connected e.g. motors, large solenoids etc.
>
> > > Geo- Hide quoted text -
>
> > - Show quoted text -

There's lots of good comments here and several concerns that are based
on urban myth.  Just as much as there will be filtering on the inputs
to car electronic boxes, there will be powerful filtering across the
likes of the starter motor, etc.  EMC/RFI testing looks at the
response on the inputs to surges, spikes, etc, but also makes sure
that supply lines and the likes do not generate and propagate
interference.  So testing is a two way activity - in and out.

The real cruncher is that no-one at all has made a statement about
experiencing any such failures - or knowing anyone who has, or hearing
of any such failure through the likes of this inter-webby thing.  The
conclusion surely is therefore that it just doesn't happen.

I quite happily have my satnav and mobile on charge while starting and
driving - I would really doubt that anyone would want to have a laptop
running while starting the car, but as they too have a dirty great
'capacitor' across the supply I wouldn't have thought problems would
have occurred.

Rob

In article <op.ue12mknhhaghkf@lucy>,
   Duncan Wood  wrote:
> > Ah so now we have a figure. Can I ask where the 60 volts comes from?
> >

> Last time looked it was 55V (TI automotive spec for semiconducters)

I gave the figure of 40 volts for a bog standard regulator - but of course
that's the differential. So if regulating to 9 volts the peak would be 49.
And of course it's simple to increase this if needed.

-- 
*The colder the X-ray table, the more of your body is required on it *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

On 2008-07-29, Duncan Wood  wrote:
> On Tue, 29 Jul 2008 13:20:43 +0100, Dave Plowman (News)  
> wrote:
>> In article
>> ,
>>     wrote:
>>>
>>> Cars have a high current inductive power source, the alternator, and
>>> the battery isnt close enough to eliminate substantial high frequency
>>> overvoltage transients in the event of load dump. This is fairly basic
>>> electronics stuff, maybe the OP should ask in sci.electronics.basics.
>>> Diy and electronics really are 2 different animals, and ukdiy is not
>>> an electronics expert group.
>>
>> There's lots of these theories doing the rounds that simply don't happen
>> in practice. And yes, I have looked at several car systems with a 'scope.
>> Of course you get rubbish on it otherwise there's be no need to filter
>> amplifier supplies etc - but those spikes ain't capable of doing damage.
>>
>
> Well the installed stuff's normally designed to cope with far worse  
> situations than you normally ever see. But if you're worried a couple of  
> 16V Zeners or VDRs are hardly expensive.

My opinion would be that most stuff without a particularly fragile
voltage regulator would be fine running on 12V from the cigarette
lighter socket.  OTOH, devices which have sensor wires running all over
the car (not your general in-car entertainment devices, etc.) may have
problems.  They have to be designed to withstand a lot of noise on any
signals and potentially harmful induced voltages on inputs.

-- 
David Taylor

"robgraham"  wrote in message 
news:1ca0f39d-cf87-41c4-b8bc-

The real cruncher is that no-one at all has made a statement about
experiencing any such failures - or knowing anyone who has, or hearing
of any such failure through the likes of this inter-webby thing.  The
conclusion surely is therefore that it just doesn't happen.

I quite happily have my satnav and mobile on charge while starting and
driving - I would really doubt that anyone would want to have a laptop
running while starting the car, but as they too have a dirty great
'capacitor' across the supply I wouldn't have thought problems would
have occurred.

Agreed. I have used all sorts of vulnerable equipment in all sorts of cars 
going back 30 years and never had any hint of the car causing spikes that 
could damage anything. I've been building all sorts of electronic stuff for 
years and long before regulators were available in a single 3 pin package so 
most of the stuff didn't have a regulator and was designed to run straight 
off the car. The only time you would go to the trouble of actually building 
a regulator was if it needed a fixed voltage for stable operator as in an 
oscillator for instance.

I'd find it difficult to list all the equipment I've used in the car, but it 
goes from valve transmitters, through to home built transistor transmitters 
and receivers, transistor RF power amps, boards with switching and logic and 
god knows what else. Never has the car enviroment been  problem beyond the 
slightly varying supply voltage, possible RF interferrence from ignition and 
protection from reverse polarity of the supply leads. Never has anything 
gone bang when starting the car due to the starter motor back emf. I have 
never encountered any mention of that in all the 
electronic/communications/broadcasting companies I  have worked for and 
frankly think it gets sinked back into the battery long before it could do 
any damage. Its just never been an issue anyone has ever mentioned as it is 
not a problem anyone has had.

Graham

On Jul 29, 1:20 pm, "Dave Plowman (News)" 
wrote:
> In article
> ,
>     wrote:
>
> > > > Its certainly an issue, car electrics are very hostile in terms of
> > > > transients, and lots of appliances just dont survive them.
>
> > > What, for example?
> > Anything electronic that isnt specifically designed to run on car
> > systems.
>
> Then it won't come with a fag lighter plug?
>
> > Also some things that are - cost cutting invertors for
> > example tend to lack the ability to survive all transients, hence wont
> > last forever.
>
> More likely damaged by overload. You'd be hard pressed to find mosfets
> that can be damaged by the sort of voltage spikes found in a car.  
>
> > >  Most of the things you plug into a fag socket don't
> > > actually run off 12 volts so will have voltage regulation somewhere -
> > > either internal or in the lead. And a standard regulator will cope with
> > > about 40 volts.
> > which isnt sufficient.
>
> Then every other piece of electronics will die too. Have you never built
> any car electronics - or is this some theory plucked from the air?  
>
> > >  Most cars these days are packed with electronics. They seem to survive
> > > this 'hostile' environment ok.
> > Theyre designed to. They have input filters that can cope with _60v.
>
> Ah so now we have a figure. Can I ask where the 60 volts comes from?  
>
> > Cars have a high current inductive power source, the alternator, and
> > the battery isnt close enough to eliminate substantial high frequency
> > overvoltage transients in the event of load dump. This is fairly basic
> > electronics stuff, maybe the OP should ask in sci.electronics.basics.
> > Diy and electronics really are 2 different animals, and ukdiy is not
> > an electronics expert group.
>
> There's lots of these theories doing the rounds that simply don't happen
> in practice. And yes, I have looked at several car systems with a 'scope.  
> Of course you get rubbish on it otherwise there's be no need to filter
> amplifier supplies etc - but those spikes ain't capable of doing damage.

How did you trigger the load dump events for these measurements?


NT

wrote in message 
news:ee57be52-c3a0-49a3-9626-b84bc62e97c2@26g2000hsk.googlegroups.com...
On Jul 29, 1:20 pm, "Dave Plowman (News)" 
wrote:
> In article
> ,
>  wrote:
>
> > > > Its certainly an issue, car electrics are very hostile in terms of
> > > > transients, and lots of appliances just dont survive them.
>
> > > What, for example?
> > Anything electronic that isnt specifically designed to run on car
> > systems.
>
> Then it won't come with a fag lighter plug?
>
> > Also some things that are - cost cutting invertors for
> > example tend to lack the ability to survive all transients, hence wont
> > last forever.
>
> More likely damaged by overload. You'd be hard pressed to find mosfets
> that can be damaged by the sort of voltage spikes found in a car.
>
> > > Most of the things you plug into a fag socket don't
> > > actually run off 12 volts so will have voltage regulation somewhere -
> > > either internal or in the lead. And a standard regulator will cope 
> > > with
> > > about 40 volts.
> > which isnt sufficient.
>
> Then every other piece of electronics will die too. Have you never built
> any car electronics - or is this some theory plucked from the air?
>
> > > Most cars these days are packed with electronics. They seem to survive
> > > this 'hostile' environment ok.
> > Theyre designed to. They have input filters that can cope with +_60v.
>
> Ah so now we have a figure. Can I ask where the 60 volts comes from?
>
> > Cars have a high current inductive power source, the alternator, and
> > the battery isnt close enough to eliminate substantial high frequency
> > overvoltage transients in the event of load dump. This is fairly basic
> > electronics stuff, maybe the OP should ask in sci.electronics.basics.
> > Diy and electronics really are 2 different animals, and ukdiy is not
> > an electronics expert group.
>
> There's lots of these theories doing the rounds that simply don't happen
> in practice. And yes, I have looked at several car systems with a 'scope.
> Of course you get rubbish on it otherwise there's be no need to filter
> amplifier supplies etc - but those spikes ain't capable of doing damage.

How did you trigger the load dump events for these measurements?


What???

He stuck a scope across the suppy and looked at the noise and spikes. End 
off.

Graham

In article <toOdnRBywJvE6BLVnZ2dnUVZ8qGdnZ2d@posted.metronet>,
   Graham  wrote:
> I'd find it difficult to list all the equipment I've used in the car,
> but it goes from valve transmitters, through to home built transistor
> transmitters and receivers, transistor RF power amps, boards with
> switching and logic and god knows what else. Never has the car
> enviroment been  problem beyond the slightly varying supply voltage,
> possible RF interferrence from ignition and protection from reverse
> polarity of the supply leads. Never has anything gone bang when
> starting the car due to the starter motor back emf. I have never
> encountered any mention of that in all the
> electronic/communications/broadcasting companies I  have worked for and
> frankly think it gets sinked back into the battery long before it could
> do any damage. Its just never been an issue anyone has ever mentioned
> as it is not a problem anyone has had.

My experience too.

-- 
*Reality is the illusion that occurs due to the lack of alcohol *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In article
,
    wrote:
> > > Cars have a high current inductive power source, the alternator, and
> > > the battery isnt close enough to eliminate substantial high
> > > frequency overvoltage transients in the event of load dump. This is
> > > fairly basic electronics stuff, maybe the OP should ask in
> > > sci.electronics.basics. Diy and electronics really are 2 different
> > > animals, and ukdiy is not an electronics expert group.
> >
> > There's lots of these theories doing the rounds that simply don't
> > happen in practice. And yes, I have looked at several car systems with
> > a 'scope.   Of course you get rubbish on it otherwise there's be no
> > need to filter amplifier supplies etc - but those spikes ain't capable
> > of doing damage.

> How did you trigger the load dump events for these measurements?

I didn't. I simply don't go around disconnecting alternators with the
engine running. I try and design stuff to be foolproof, idiot proof even -
but not c**t proof.

-- 
*I'm not a complete idiot, some parts are missing *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

On Jul 28, 7:23 pm, "Dave Plowman (News)" 
wrote:
> I'm not quite sure how you'd get 'surges' in power in a car, given it has
> an extremely low impedance vast capacitor sitting across the line - the
> battery.

  Assumptions contradict well proven standards.  Load dump is defined
up to 270 volts on the 12 volts.  All car electronics includes designs
to make load dump irrelevant.  But some appliances selling on the
cheap may simply forget that option.

  Most all semiconductor manufacturers make power supply chips so that
12 volts can supply regulated voltages to electronics.  Then they make
special versions for automotive use due to higher voltages such as
load dump.  National Semiconductor has a specific line just for
automotive use.  Does you adaptor manufacturer used the standard and
cheap voltage regulators - or those designed for automotive use.

  Standards that define load dump including SAE J1455 and  ISO
7637-1.  Load dump can be defined by:
>>  Peak voltage 80 to 100 volts
>>  Duration 300 to 400 milliseconds
>>  Series resistance 0.2 to 1 ohms

  Some designs call for a protection circuit that can withstand up to
270 volts and 50 joules.  Why do some manufacturers sell the
equivalent 12 volt power source for more money?  What does the
manufacturer spec say about load dump?

On Jul 29, 11:54 pm, w_tom  wrote:
> On Jul 28, 7:23 pm, "Dave Plowman (News)" 
> wrote:
>
> > I'm not quite sure how you'd get 'surges' in power in a car, given it has
> > an extremely low impedance vast capacitor sitting across the line - the
> > battery.
>
>   Assumptions contradict well proven standards.  Load dump is defined
> up to 270 volts on the 12 volts.  All car electronics includes designs
> to make load dump irrelevant.  But some appliances selling on the
> cheap may simply forget that option.
>
>   Most all semiconductor manufacturers make power supply chips so that
> 12 volts can supply regulated voltages to electronics.  Then they make
> special versions for automotive use due to higher voltages such as
> load dump.  National Semiconductor has a specific line just for
> automotive use.  Does you adaptor manufacturer used the standard and
> cheap voltage regulators - or those designed for automotive use.

Very often, there's feck all difference between parts supplied for
normal or other environments. It's just not economical to do
otherwise. Look at the way the supply of "military" grade silicon
virtually disappeared.

Selling into the automotive market relies on implementing, and being
able to prove you've implemented very strict QA processes. Another
aspect is traceability of supply. Don't even mention the liability
terms that automotive manufacturers will try to apply.

MBQ

On Jul 29, 11:27 pm, "Dave Plowman (News)" 
wrote:
> In article
> ,
>     wrote:

> > > > Cars have a high current inductive power source, the alternator, and
> > > > the battery isnt close enough to eliminate substantial high
> > > > frequency overvoltage transients in the event of load dump. This is
> > > > fairly basic electronics stuff, maybe the OP should ask in
> > > > sci.electronics.basics. Diy and electronics really are 2 different
> > > > animals, and ukdiy is not an electronics expert group.
>
> > > There's lots of these theories doing the rounds that simply don't
> > > happen in practice. And yes, I have looked at several car systems with
> > > a 'scope.   Of course you get rubbish on it otherwise there's be no
> > > need to filter amplifier supplies etc - but those spikes ain't capable
> > > of doing damage.
> > How did you trigger the load dump events for these measurements?
>
> I didn't. I simply don't go around disconnecting alternators with the
> engine running. I try and design stuff to be foolproof, idiot proof even > but not c**t proof.

That would explain your failure to see the spikes. Try repeatedly
switching off the rear window heater while measuring next time. Then
try it for real: switch off all accessories and waggle the loose
battery connection. Dont have your laptop connected :)

If the op wants to play chance games with their lappy they can, but at
least they're more aware of the problem now.

If these events didnt occur IRL no-one would write about them, and car
electronics designers wouldnt design equipment to withstand them. They
do.


NT

On Jul 29, 8:53 pm, "Graham"  wrote:
> "robgraham"  wrote in message
>
> news:1ca0f39d-cf87-41c4-b8bc-
>
> The real cruncher is that no-one at all has made a statement about
> experiencing any such failures - or knowing anyone who has, or hearing
> of any such failure through the likes of this inter-webby thing.  The
> conclusion surely is therefore that it just doesn't happen.
>
> I quite happily have my satnav and mobile on charge while starting and
> driving - I would really doubt that anyone would want to have a laptop
> running while starting the car, but as they too have a dirty great
> 'capacitor' across the supply I wouldn't have thought problems would
> have occurred.
>
> Agreed. I have used all sorts of vulnerable equipment in all sorts of cars
> going back 30 years and never had any hint of the car causing spikes that
> could damage anything. I've been building all sorts of electronic stuff for
> years and long before regulators were available in a single 3 pin package so
> most of the stuff didn't have a regulator and was designed to run straight
> off the car. The only time you would go to the trouble of actually building
> a regulator was if it needed a fixed voltage for stable operator as in an
> oscillator for instance.
>
> I'd find it difficult to list all the equipment I've used in the car, but it
> goes from valve transmitters, through to home built transistor transmitters
> and receivers, transistor RF power amps, boards with switching and logic and
> god knows what else. Never has the car enviroment been  problem beyond the
> slightly varying supply voltage, possible RF interferrence from ignition and
> protection from reverse polarity of the supply leads. Never has anything
> gone bang when starting the car due to the starter motor back emf. I have
> never encountered any mention of that in all the
> electronic/communications/broadcasting companies I  have worked for and
> frankly think it gets sinked back into the battery long before it could do
> any damage. Its just never been an issue anyone has ever mentioned as it is
> not a problem anyone has had.
>
> Graham

Disconnection of the starter motor is not the problem. The inductive
current source is the alternator, and this is producing more or less
nothing during starting.


NT

On Wed, 30 Jul 2008 13:53:04 +0100,  wrote:

> On Jul 29, 11:27 pm, "Dave Plowman (News)" 
> wrote:
>> In article
>> ,
>>     wrote:
>
>> > > > Cars have a high current inductive power source, the alternator,  
>> and
>> > > > the battery isnt close enough to eliminate substantial high
>> > > > frequency overvoltage transients in the event of load dump. This  
>> is
>> > > > fairly basic electronics stuff, maybe the OP should ask in
>> > > > sci.electronics.basics. Diy and electronics really are 2 different
>> > > > animals, and ukdiy is not an electronics expert group.
>>
>> > > There's lots of these theories doing the rounds that simply don't
>> > > happen in practice. And yes, I have looked at several car systems  
>> with
>> > > a 'scope.   Of course you get rubbish on it otherwise there's be no
>> > > need to filter amplifier supplies etc - but those spikes ain't  
>> capable
>> > > of doing damage.
>> > How did you trigger the load dump events for these measurements?
>>
>> I didn't. I simply don't go around disconnecting alternators with the
>> engine running. I try and design stuff to be foolproof, idiot proof  
>> even -
>> but not c**t proof.
>
> That would explain your failure to see the spikes. Try repeatedly
> switching off the rear window heater while measuring next time. Then
> try it for real: switch off all accessories and waggle the loose
> battery connection. Dont have your laptop connected :)
>
> If the op wants to play chance games with their lappy they can, but at
> least they're more aware of the problem now.
>
> If these events didnt occur IRL no-one would write about them, and car
> electronics designers wouldnt design equipment to withstand them. They
> do.
>
>
> NT


Most of us here don't have loose battery connections.

wrote in message 
news:35b118f9-1579-4360-a4ed-5691bd61e131@34g2000hsf.googlegroups.com...
On Jul 29, 8:53 pm, "Graham"  wrote:
> "robgraham"  wrote in message
>
> news:1ca0f39d-cf87-41c4-b8bc-
>
> The real cruncher is that no-one at all has made a statement about
> experiencing any such failures - or knowing anyone who has, or hearing
> of any such failure through the likes of this inter-webby thing. The
> conclusion surely is therefore that it just doesn't happen.
>
> I quite happily have my satnav and mobile on charge while starting and
> driving - I would really doubt that anyone would want to have a laptop
> running while starting the car, but as they too have a dirty great
> 'capacitor' across the supply I wouldn't have thought problems would
> have occurred.
>
> Agreed. I have used all sorts of vulnerable equipment in all sorts of cars
> going back 30 years and never had any hint of the car causing spikes that
> could damage anything. I've been building all sorts of electronic stuff 
> for
> years and long before regulators were available in a single 3 pin package 
> so
> most of the stuff didn't have a regulator and was designed to run straight
> off the car. The only time you would go to the trouble of actually 
> building
> a regulator was if it needed a fixed voltage for stable operator as in an
> oscillator for instance.
>
> I'd find it difficult to list all the equipment I've used in the car, but 
> it
> goes from valve transmitters, through to home built transistor 
> transmitters
> and receivers, transistor RF power amps, boards with switching and logic 
> and
> god knows what else. Never has the car enviroment been problem beyond the
> slightly varying supply voltage, possible RF interferrence from ignition 
> and
> protection from reverse polarity of the supply leads. Never has anything
> gone bang when starting the car due to the starter motor back emf. I have
> never encountered any mention of that in all the
> electronic/communications/broadcasting companies I have worked for and
> frankly think it gets sinked back into the battery long before it could do
> any damage. Its just never been an issue anyone has ever mentioned as it 
> is
> not a problem anyone has had.
>
> Graham

Disconnection of the starter motor is not the problem. The inductive
current source is the alternator, and this is producing more or less
nothing during starting.

So as previously stated, there is no problem. You carry on with your bad 
self and I'll carry on without the problems I've not had.

Graham

In article <op.ue3wiyg6haghkf@lucy>,
   Duncan Wood  wrote:
> Most of us here don't have loose battery connections.

And if we did the car wouldn't start which means 'current dump' into an
accessory couldn't happen...

-- 
*According to my calculations, the problem doesn't exist.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In article
,
    wrote:
> > I didn't. I simply don't go around disconnecting alternators with the
> > engine running. I try and design stuff to be foolproof, idiot proof
> > even - but not c**t proof.

> That would explain your failure to see the spikes. Try repeatedly
> switching off the rear window heater while measuring next time.

What's that supposed to do?

> Then try it for real: switch off all accessories and waggle the loose
> battery connection. Dont have your laptop connected :)

Err, why are you deliberately introducing a red herring? If a battery
terminal is loose the car won't start. 

> If the op wants to play chance games with their lappy they can, but at
> least they're more aware of the problem now.

You use a laptop on the move? Takes all types.

> If these events didnt occur IRL no-one would write about them, and car
> electronics designers wouldnt design equipment to withstand them. They
> do.

Including the PS built into the fag lighter adaptor?

I'm not denying you could possibly mess up something by adapting it to run
off a fag lighter socket - but that wasn't the question.

And I've got lots of home designed electronics in one car where I made
absolutely no provision for the sort of over voltage you imply. Without
failure.

-- 
*If you ate pasta and anti-pasta, would you still be hungry?

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In article , Dave Plowman (News) 
says...
> > Never has anything gone bang when
> > starting the car due to the starter motor back emf. I have never
> > encountered any mention of that in all the
> > electronic/communications/broadcasting companies I  have worked for and
> > frankly think it gets sinked back into the battery long before it could
> > do any damage. Its just never been an issue anyone has ever mentioned
> > as it is not a problem anyone has had.
> 
> My experience too.
> 
And last night I started my Renault Premium which had my Satnav plugged 
into the 24V socket and a 300W Mains Inverter plugged into the 12V 
socket and my lappy plugged into that. Apart from them cutting out 
momentarily as the ignition key changed positions, they kept working 
throughout. It's not the first time I've done it either. At one point, 
it was happening several times a night when I was doing a night trunk 
for a pallet company. Lappy is still working fine, inverter is still 
working fine. So is moby and Satnav.

And I can guarantee that any back EMF you'd get from a 24V starter 
motor on a 12 litre diesel engine is going to far exceed anything you'd 
get from a poxy car one.


-- 
Conor

I only please one person per day. Today is not your day. Tomorrow isn't 
looking good either. - Scott Adams

In article <cc3c2337-405c-4e1c-9c7e-35359c976734
@b1g2000hsg.googlegroups.com>,  says...

> That would explain your failure to see the spikes. Try repeatedly
> switching off the rear window heater while measuring next time. Then
> try it for real: switch off all accessories and waggle the loose
> battery connection. Dont have your laptop connected :)
> 
Fuck all happened. Difference is I had the night heater in the truck 
instead of a heated window. A night heater is a bit of kit which has an 
electrode which heats up diesel and a fan to blow the resulting hot air 
into the cab. Works like central heating in the fact that you set a 
temperature and it comes on and off to maintain that.

A night heater draws more current than a window heater and the 
electrical noise from the fan far exceeds that of the window heater to 
the point where it can be seen as RF interference on a TV.

And my laptop still works.

So again, you're talking out of your arse.

-- 
Conor

I only please one person per day. Today is not your day. Tomorrow isn't 
looking good either. - Scott Adams

In article , Dave Plowman (News) 
says...

> You use a laptop on the move? Takes all types.

I use my laptop in my lorry. Its exposed to far more electrical noise 
and far higher potential back EMF than you'd get in a car yet my lappy 
is working fine.

-- 
Conor

I only please one person per day. Today is not your day. Tomorrow isn't 
looking good either. - Scott Adams

"Conor"  wrote in message 
news:6fbp7bFar3a0U4@mid.individual.net...
> In article <cc3c2337-405c-4e1c-9c7e-35359c976734
> @b1g2000hsg.googlegroups.com>,  says...
>
>> That would explain your failure to see the spikes. Try repeatedly
>> switching off the rear window heater while measuring next time. Then
>> try it for real: switch off all accessories and waggle the loose
>> battery connection. Dont have your laptop connected :)
>>
> Fuck all happened. Difference is I had the night heater in the truck
> instead of a heated window. A night heater is a bit of kit which has an
> electrode which heats up diesel and a fan to blow the resulting hot air
> into the cab. Works like central heating in the fact that you set a
> temperature and it comes on and off to maintain that.

Yeah, Eberspächer. Got one in my campervan. Brilliant things. Even during -6 
nights I was almost too warm. and had to turn the themostat down.

Graham

In article <59udnUfUDd8MLg3VRVnyvgA@posted.metronet>, Graham says...
> 
> "Conor"  wrote in message 
> news:6fbp7bFar3a0U4@mid.individual.net...
> > In article <cc3c2337-405c-4e1c-9c7e-35359c976734
> > @b1g2000hsg.googlegroups.com>,  says...
> >
> >> That would explain your failure to see the spikes. Try repeatedly
> >> switching off the rear window heater while measuring next time. Then
> >> try it for real: switch off all accessories and waggle the loose
> >> battery connection. Dont have your laptop connected :)
> >>
> > Fuck all happened. Difference is I had the night heater in the truck
> > instead of a heated window. A night heater is a bit of kit which has an
> > electrode which heats up diesel and a fan to blow the resulting hot air
> > into the cab. Works like central heating in the fact that you set a
> > temperature and it comes on and off to maintain that.
> 
> Yeah, Eberspächer. Got one in my campervan. Brilliant things. Even during -6 
> nights I was almost too warm. and had to turn the themostat down.
> 
That's the jobbie. Only downside to them is getting them to fire up for 
the first time after a summer being unused.


-- 
Conor

I only please one person per day. Today is not your day. Tomorrow isn't 
looking good either. - Scott Adams

On Jul 30, 7:11 pm, Conor  wrote:
> In article <cc3c2337-405c-4e1c-9c7e-35359c976734
> @b1g2000hsg.googlegroups.com>,  says...
>
> > That would explain your failure to see the spikes. Try repeatedly
> > switching off the rear window heater while measuring next time. Then
> > try it for real: switch off all accessories and waggle the loose
> > battery connection. Dont have your laptop connected :)
>
> Fuck all happened. Difference is I had the night heater in the truck
> instead of a heated window. A night heater is a bit of kit which has an
> electrode which heats up diesel and a fan to blow the resulting hot air
> into the cab. Works like central heating in the fact that you set a
> temperature and it comes on and off to maintain that.
>
> A night heater draws more current than a window heater and the
> electrical noise from the fan far exceeds that of the window heater to
> the point where it can be seen as RF interference on a TV.
>
> And my laptop still works.
>
> So again, you're talking out of your arse.

Can you read ok Conor? 'Dont disconnect the battery with the laptop
connected' is what was said. Tell you what, since theres no problem
why dont you try it and prove it to us.


NT

Graham wrote:

> So as previously stated, there is no problem. You carry on with your bad 
> self and I'll carry on without the problems I've not had.

If there's no problem why is the subject of 'load dump' and other 
transient overvoltages taken so seriously in the automotive electronics 
industry?  Why are detailed specifications and standards written and a 
great deal of testing done?  Why do the semiconductor manufacturers 
develop and make automotive-rated devices?  Why does Google return over 
7,000 hits for "automotive load dump" and nearly 84,000 for "load dump" 
most of them probably automotive-related?

-- 
Andy

On Jul 30, 6:20 pm, "Dave Plowman (News)" 
wrote:
> In article
> ,
>     wrote:
>
> > > I didn't. I simply don't go around disconnecting alternators with the
> > > engine running. I try and design stuff to be foolproof, idiot proof
> > > even - but not c**t proof.
> > That would explain your failure to see the spikes. Try repeatedly
> > switching off the rear window heater while measuring next time.
>
> What's that supposed to do?
>
> > Then try it for real: switch off all accessories and waggle the loose
> > battery connection. Dont have your laptop connected :)
>
> Err, why are you deliberately introducing a red herring? If a battery
> terminal is loose the car won't start.
>
> > If the op wants to play chance games with their lappy they can, but at
> > least they're more aware of the problem now.
>
> You use a laptop on the move? Takes all types.
>
> > If these events didnt occur IRL no-one would write about them, and car
> > electronics designers wouldnt design equipment to withstand them. They
> > do.
>
> Including the PS built into the fag lighter adaptor?
>
> I'm not denying you could possibly mess up something by adapting it to run
> off a fag lighter socket - but that wasn't the question.
>
> And I've got lots of home designed electronics in one car where I made
> absolutely no provision for the sort of over voltage you imply. Without
> failure.

I'm surprised you dont seem to spot the flaws in these points. But I'm
not really concerned, enjoy your appliances.


NT

On 2008-07-30 19:11:52 +0100, Conor  said:

> In article <cc3c2337-405c-4e1c-9c7e-35359c976734
> @b1g2000hsg.googlegroups.com>,  says...
> 
>> That would explain your failure to see the spikes. Try repeatedly
>> switching off the rear window heater while measuring next time. Then
>> try it for real: switch off all accessories and waggle the loose
>> battery connection. Dont have your laptop connected :)
>> 
> Fuck all happened. Difference is I had the night heater in the truck
> instead of a heated window. A night heater is a bit of kit which has an
> electrode which heats up diesel and a fan to blow the resulting hot air
> into the cab. Works like central heating in the fact that you set a
> temperature and it comes on and off to maintain that.
> 
> A night heater draws more current than a window heater and the
> electrical noise from the fan far exceeds that of the window heater to
> the point where it can be seen as RF interference on a TV.
> 
> And my laptop still works.
> 
> So again, you're talking out of your arse.

Really all that you can deduce from that is that nothing bad happens in 
your environment.   It doesn't give the data to say that it can never 
happen in other cases.

In my early engineering career, I designed electronics, control and 
communication systems that were often fitted into military vehicles of 
various types.

In general it was necessary to incorporate various filtering and 
protection into the DC supplies to the electronics, because of 
electrical spikes and noise from the vehicle systems.       Primarily, 
this was to avoid damage to certain sensitive semiconductors  in the 
equipment and did so successfully.

The far harder problem was dealing with the sensitivity of the radio 
receivers, that were working in the 2-30MHz range from being swamped by 
the general electrical noise.

For example, on a tank, when the turret was rotated, one could find 
sharp rising spikes of 600-800v on some of the wiring.

I suspect that in a typical domestic car and possibly even a commercial 
truck, the potential for problems is not as great and certainly 
electronics has been improved from the EMC perspective over the last 
decade.     Nonetheless, the mechanisms for bad things to happen are 
certainly present in a motor vehicle.

On Thu, 31 Jul 2008 01:57:40 +0100, Andy Wade  
 wrote:

> Graham wrote:
>
>> So as previously stated, there is no problem. You carry on with your  
>> bad self and I'll carry on without the problems I've not had.
>
> If there's no problem why is the subject of 'load dump' and other  
> transient overvoltages taken so seriously in the automotive electronics  
> industry?  Why are detailed specifications and standards written and a  
> great deal of testing done?  Why do the semiconductor manufacturers  
> develop and make automotive-rated devices?  Why does Google return over  
> 7,000 hits for "automotive load dump" and nearly 84,000 for "load dump"  
> most of them probably automotive-related?
>


Because if the elctronics inside the car failed at that point then a loose  
battery lead would write the car off. Which would be highly embarassing to  
have to explain on watchdog & have enormous liability issues for anything  
safety critical. & it's most likely to occur during initial startup &  
subsequent servicing, your laptop/pda etc. are orders of magnitude more  
likely to be stolen because they didn't fit laminated glass to the windows.

"Dave Plowman (News)"  gurgled happily, sounding
much like they were saying:

>> Most of us here don't have loose battery connections.

> And if we did the car wouldn't start

Umm, cobblers. Many's the time I've come to remove a battery terminal 
only to find it's loose - and the thing's been running fine.

"Dave Plowman (News)"  wrote in message 
news:4fc718fd8cdave@davenoise.co.uk...
> In article
> ,
>    wrote:
>> > I didn't. I simply don't go around disconnecting alternators with the
>> > engine running. I try and design stuff to be foolproof, idiot proof
>> > even - but not c**t proof.
>
>> That would explain your failure to see the spikes. Try repeatedly
>> switching off the rear window heater while measuring next time.
>
> What's that supposed to do?
>
>> Then try it for real: switch off all accessories and waggle the loose
>> battery connection. Dont have your laptop connected :)
>
> Err, why are you deliberately introducing a red herring? If a battery
> terminal is loose the car won't start.
>
>> If the op wants to play chance games with their lappy they can, but at
>> least they're more aware of the problem now.
>
> You use a laptop on the move? Takes all types.

Ever heard of passengers? My lot are fiddling with countless gadgets while 
on the move. Some connected to car. The wife has been known to bid on ebay 
while we are travelling.

Graham

"Graham"  wrote in message
>
> Ever heard of passengers? My lot are fiddling with countless gadgets while 
> on the move. Some connected to car. The wife has been known to bid on ebay 
> while we are travelling.

Maybe for a new laptop, just in case the old one fries due to loose battery 
terminals :-) Oh, wait a minute, can't happen, the car would never start, 
not with a loose battery terminal - the electrons would go on strike..... 
what a load of twaddle people spout.

Julian.

In article <4891478d@qaanaaq>,
   Andy Hall <andyh@hall.nospam> wrote:
> The far harder problem was dealing with the sensitivity of the radio 
> receivers, that were working in the 2-30MHz range from being swamped by 
> the general electrical noise.

That's a different matter from the topic under discussion.

> For example, on a tank, when the turret was rotated, one could find 
> sharp rising spikes of 600-800v on some of the wiring.

So you don't use that wiring as pickup points for accessories.

> I suspect that in a typical domestic car and possibly even a commercial 
> truck, the potential for problems is not as great and certainly 
> electronics has been improved from the EMC perspective over the last 
> decade.     Nonetheless, the mechanisms for bad things to happen are 
> certainly present in a motor vehicle.

What you're implying is that laptop makers who supply leads for car use
are unaware of this?

-- 
*Do infants enjoy infancy as much as adults enjoy adultery? *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In article ,
   Andy Wade  wrote:
> Graham wrote:

> > So as previously stated, there is no problem. You carry on with your
> > bad self and I'll carry on without the problems I've not had.

> If there's no problem why is the subject of 'load dump' and other 
> transient overvoltages taken so seriously in the automotive electronics 
> industry?  Why are detailed specifications and standards written and a 
> great deal of testing done?  Why do the semiconductor manufacturers 
> develop and make automotive-rated devices?  Why does Google return over 
> 7,000 hits for "automotive load dump" and nearly 84,000 for "load dump" 
> most of them probably automotive-related?

People have too much time on their hands. It's simply not a problem in
practice.

-- 
*Why is the word abbreviation so long? *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In article ,
   Adrian  wrote:
> >> Most of us here don't have loose battery connections.

> > And if we did the car wouldn't start

> Umm, cobblers. Many's the time I've come to remove a battery terminal 
> only to find it's loose - and the thing's been running fine.

Well if if it's capable of handling starter current it's not going to
cause problems with the much lower currents from an alternator...

-- 
*Monday is an awful way to spend 1/7th of your life *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

On 2008-07-31 11:21:45 +0100, "Dave Plowman (News)" 
 said:

> In article <4891478d@qaanaaq>,
>    Andy Hall <andyh@hall.nospam> wrote:
>> The far harder problem was dealing with the sensitivity of the radio
>> receivers, that were working in the 2-30MHz range from being swamped by
>> the general electrical noise.
> 
> That's a different matter from the topic under discussion.

Of course.     I'm simply making the point that conducted spikes in a 
vehicle do have the potential to cause damage.

> 
>> For example, on a tank, when the turret was rotated, one could find
>> sharp rising spikes of 600-800v on some of the wiring.
> 
> So you don't use that wiring as pickup points for accessories.

In a tank you don't get a lot of choice.



> 
>> I suspect that in a typical domestic car and possibly even a commercial
>> truck, the potential for problems is not as great and certainly
>> electronics has been improved from the EMC perspective over the last
>> decade.     Nonetheless, the mechanisms for bad things to happen are
>> certainly present in a motor vehicle.
> 
> What you're implying is that laptop makers who supply leads for car use
> are unaware of this?

I would say that that depends on the laptop maker and the accessory.    
 If the accessory comes from the manufacturer of the laptop as an 
adaptor specifically for the purpose, then I would expect them to have 
done diligent engineering and if it breaks they get to own the problem. 
   If I were to buy a cheap Chinese generic accessory, I would have 
little confidence in the engineering and not expect redress.   Ergo, I 
would not buy cheap Chinese car accessory lead.

On 2008-07-31, Dave Plowman (News)  wrote:
> In article ,
>    Adrian  wrote:
>> >> Most of us here don't have loose battery connections.
>
>> > And if we did the car wouldn't start
>
>> Umm, cobblers. Many's the time I've come to remove a battery terminal 
>> only to find it's loose - and the thing's been running fine.
>
> Well if if it's capable of handling starter current it's not going to
> cause problems with the much lower currents from an alternator...

The car is rarely moving when the starter is being used.

-- 
David Taylor

In article ,
   David Taylor  wrote:
> On 2008-07-31, Dave Plowman (News)  wrote:
> > In article ,
> >    Adrian  wrote:
> >> >> Most of us here don't have loose battery connections.
> >
> >> > And if we did the car wouldn't start
> >
> >> Umm, cobblers. Many's the time I've come to remove a battery terminal 
> >> only to find it's loose - and the thing's been running fine.
> >
> > Well if if it's capable of handling starter current it's not going to
> > cause problems with the much lower curren