[DerAlte]

@anthiltg, relax, the surges that come on the +12V line are low energy content. Most of the 'surges' are due to the relay contact bounce in the higher power circuits - lighting, AC, etc.. But these don't reach the +12V line as surges (spike on load-side of relay, not coil-side), only as RF interference. The largest surge producer should be the Starter solenoid (Starter is largest current consumer in a car + mechanical switching), but one hears seldom, if ever, about electronic equipment getting bricked due to that. By convention, all loads must decouple on starter crank (signal from the Key Switch comes before the starter solenoid engages, and goes away after the solenoid disengages), including lighting, AC, music system etc.

Most electronic equipment in the car have a surge suppressor / RF spike suppressor at the 12V input. Beyond that, equipments that have a switching DC-DC supply - like an off-the-shelf Car PC power supply - are not affected by design. Downstream consumers of the PSU - motherboard, HDD, etc. - are functionally disabled by the PSU ('unreliable DC voltage' signal) during the crank cycle, since the Key Switch signal is connected to it. Haven't heard of anyone who has installed a Car PC ever complaining about a PSU failing due to surges.

If one is carrying over memories of laptop PSU and other switched mode wall supplies like chargers etc. blowing up due to surge on the domestic electricity line: no comparison. That surge is high energy (lightning strike, transformer malfunction etc.), and results in a 2x (at least) surge voltage - of the order of 400V or more.

[Sutripta]

Originally Posted by anthiltg

Actuall idea is to install pc(media/audio) inside the car. It would not be good to directly to put +12V battery directly interfaced to pc without having knowledge of understanding the behaviour of a battery, even though the system(carpc) has power supply management, This should not burden my pocket cost of direct mistake.

Is it a proper carputer, or something you are jury rigging for use in a car?

Regards
Sutripta

[DerAlte]

Originally Posted by Sutripta

Is it a proper carputer, or something you are jury rigging for use in a car?

Regards
Sutripta

Err... What is the difference, dada? You are breaking the heart of all the DIY guys out there! :(

[Sutripta]

Originally Posted by DerAlte

What is the difference, dada?

Difference between fit and forget, and fit and worry

Regards
Sutripta

PS Dada to the Old One?

[DerAlte]

No longer 'fit and worry'! Even DIY people use robust off-the-shelf components rather than jury-rigging sub-assemblies. Gone are the days of buying components, making a PCB and soldering components (unless you are creating a design never made before by anyone) - OTS sub-assemblies are cheaper and hassle-free.

PS: Because you are dada beyond age-differences!!!

[Sutripta]

Originally Posted by DerAlte

Even DIY people use robust off-the-shelf components rather than jury-rigging sub-assemblies.

I think we should leave the trials and tribulations of following Linsley Hood and Steve Ciarcia etc. to some electronics forum. And electronics for use in automobiles a very different kettle of fish. TBhp certainly not the place for it!

Regards
Sutripta

[DerAlte]

http://www.team-bhp.com/forum/diy-do...er-thread.html
http://www.team-bhp.com/forum/ask-gu...-fiesta-s.html
http://www.team-bhp.com/forum/diy-do...ter-setup.html
http://www.team-bhp.com/forum/diy-do...-carputer.html
http://www.team-bhp.com/forum/diy-do...brication.html
http://www.team-bhp.com/forum/diy-do...ing-stage.html
http://www.team-bhp.com/forum/diy-do...tallation.html

Team-BHP is certainly the place for it!!! Electronics for automobiles is the same as that in consumer and industrial electronics today. Nothing esoteric there, other than the reliability and environmental testing that goes in for the function-critical ECUs. Even for the non-critical parts like Car PCs, the scene is not that bad!

Linsey Hood, Steve Ciarcia? The world has moved on since then, dada!

[Aroy]

Originally Posted by DerAlte

Team-BHP is certainly the place for it!!! Electronics for automobiles is the same as that in consumer and industrial electronics today. Nothing esoteric there, other than the reliability and environmental testing that goes in for the function-critical ECUs. Even for the non-critical parts like Car PCs, the scene is not that bad!

Any thing to do with cars is in Team BHP's purview.

That said please keep in mind

. Consumer electronics is at the lowest level of specifications and reliability outside the specs.
. Industrial Electronics comes next
. Military Specs (MIL) are the toughest.

With Temperature range of -55 to +125 degrees and extreme shock & vibration as well as radiation hardening conditions, the MIL specifications are nearest to the conditions faced by vehicles operated in hostile environment (Arctic to Sahara). Even for those who drive mostly in the city, the heat and high humidity of Chennai or frigid temperatures of Mid West US, would ruin most consumer electronics in the long run.

That is why vehicle electronics needs to have specifications between the Industrial and Military. Now you have an inkling of why European Vehicle Electronics fails much more than the Japanese ones. The Japs simply have tighter specifications! (This is contrast to the Military Vehicles, where European or US vehicle electronics is extremely robust).

[Sutripta]

Originally Posted by DerAlte

Linsey Hood, Steve Ciarcia? The world has moved on since then, dada!

Mentioned those as an inside joke. Only people of our age would know what we are talking about!

Electronics for automobiles is the same as that in consumer and industrial electronics today.

Disagree. Else the qualifiers (consumer, industrial etc) would not have been necessary.

Anyway, lets say our PoV/ perceptions etc differ (so what else is new ) and close 'our' discussion. Esp. since the OP seems to have got some answer.

@ARoy: In my mind the question of this thread is not primarily about reliability, but about the effect of less than perfect power sources on various modules.

Regards
Sutripta

[Aroy]

Originally Posted by Sutripta

@ARoy: In my mind the question of this thread is not primarily about reliability, but about the effect of less than perfect power sources on various modules.

Regards
Sutripta

Reliability is "will not fail" under working conditions. Of course the description of "working conditions" varies. In my opinion reliability should ensure that the device works under
. Power supply voltage variation of +- 30% (or 9V to 16V for 12V systems)
. Temperature range the vehicle will be subjected to plus a cushion : -30 to +100 degrees centigrade. In fact at 50 degree ambient of a desert, you can expect some components to reach 100 degrees.
. Vibration & jerks the vehicle is expected to experience, including emergency case
. Humidity upto 100% at 45 degrees or more

These are pretty tough conditions, and in my knowledge most industrial specs do not come close. So In my opinion there should be a spec in between the Industrial and MIL to cater to automotive electronics.

[Sutripta]

Originally Posted by Aroy

Reliability is "will not fail" under working conditions. Of course the description of "working conditions" varies.

Question is of 'Working as expected/ working as advertised'.
Reliability (as in 'will not fail') is just one aspect of the matrix.

These are pretty tough conditions, and in my knowledge most industrial specs do not come close. So In my opinion there should be a spec in between the Industrial and MIL to cater to automotive electronics.

I think there are. (Though not being laid down by the US DoD, these can be taken, as Johnny Depp said, guidelines rather than rules.)
There are enough members who are working in electronics/ software in the auto industry. I think they can provide more comprehensive answers.


Regards
Sutripta

[vina]

Originally Posted by Aroy

Reliability is "will not fail" under working conditions. Of course the description of "working conditions" varies. In my opinion reliability should ensure that the device works under
. Power supply voltage variation of +- 30% (or 9V to 16V for 12V systems)
. Temperature range the vehicle will be subjected to plus a cushion : -30 to +100 degrees centigrade. In fact at 50 degree ambient of a desert, you can expect some components to reach 100 degrees.
. Vibration & jerks the vehicle is expected to experience, including emergency case
. Humidity upto 100% at 45 degrees or more

These are pretty tough conditions, and in my knowledge most industrial specs do not come close. So In my opinion there should be a spec in between the Industrial and MIL to cater to automotive electronics.

Originally Posted by Sutripta

Question is of 'Working as expected/ working as advertised'.
Reliability (as in 'will not fail') is just one aspect of the matrix.


I think there are. (Though not being laid down by the US DoD, these can be taken, as Johnny Depp said, guidelines rather than rules.)
There are enough members who are working in electronics/ software in the auto industry. I think they can provide more comprehensive answers.


Regards
Sutripta

I think this discussion would better be on this thread http://www.team-bhp.com/forum/techni...liability.html



Automotive grade ICs usually conform to -40C to 125C for temperature, (internal design targets are usually up to 150C). However this is junction temperature, the package temperature is usually lower.

Supply voltage requirements for all chips depend on the application in question - e.g Cellphone chips for example work off 4.3V to 2.7V (Li-ion batteries charge at 4.2V and terminal voltage is roughly 2.9V at full discharge, rest is margin). However all electronic systems usually separate the power management function from the rest of the system, the exception are high-power systems that must be connected directly to raw power source (battery or AC-DC converters etc.). The systems that do not connect to raw power source but get their power via a power management unit (PMU) usually support +/-5% supply variation - though they are designed for +/-10%. The spec for automotive/MIL is usually +/-10% if there is a PMU expected in the system.

PMU chips are specified based on the raw-power. For Cars lead-acid battery voltage (during charging) can be as high as 16V during charging and as low as 8V at full discharge - this is the reason PMU section is designed for such variation. It is not because anybody want +/-30%.


To meet humidity requirements most of the time package is hermetically sealed - but this depends on the buyers of the chip (e.g. a chip that will remain inside the cabin doesn't have to get an expensive package).




The "grades" of the chips are usually general guidelines only. Very few consumer grade ICs are acutally designed for 85C - chips are designed usually for 125C because even in consumer applications customers routinely demand 125C of junction temperature (cheap poor package + poor thermal design of equipment chassis + 45C temperature in sun can easily cause juntion temperature to be 125C) due to system cost constraints. Similarly chips that military uses need not really conform to the usual MIL standards (of which there are many) - some chips for example will not work properly unless cooled by liquid nitrogen.

[anthiltg]

Originally Posted by DerAlte

@anthiltg, relax, the surges that come on the +12V line are low energy content. Most of the 'surges' are due to the relay contact bounce in the higher power circuits - lighting, AC, etc.. But these don't reach the +12V line as surges (spike on load-side of relay, not coil-side), only as RF interference. The largest surge producer should be the Starter solenoid (Starter is largest current consumer in a car + mechanical switching), but one hears seldom, if ever, about electronic equipment getting bricked due to that. By convention, all loads must decouple on starter crank (signal from the Key Switch comes before the starter solenoid engages, and goes away after the solenoid disengages), including lighting, AC, music system etc.

Most electronic equipment in the car have a surge suppressor / RF spike suppressor at the 12V input. Beyond that, equipments that have a switching DC-DC supply - like an off-the-shelf Car PC power supply - are not affected by design. Downstream consumers of the PSU - motherboard, HDD, etc. - are functionally disabled by the PSU ('unreliable DC voltage' signal) during the crank cycle, since the Key Switch signal is connected to it. Haven't heard of anyone who has installed a Car PC ever complaining about a PSU failing due to surges.

If one is carrying over memories of laptop PSU and other switched mode wall supplies like chargers etc. blowing up due to surge on the domestic electricity line: no comparison. That surge is high energy (lightning strike, transformer malfunction etc.), and results in a 2x (at least) surge voltage - of the order of 400V or more.

ok, the board i am using for car pc has power supply management unit, but still on the safer side any electronics that i can place between relay and the carpc. [knowing the factor its decoupled and isolated while ignition]. Any more prevention is still better.