Electrical Noise in an Automotive Environment

[RomanM]

I am considering developing some products for the automotive industry and I need to know what kind of transient voltage spikes I have to allow for. What guidelines are there to follow or better yet, some 'rule of thumb' guidelines. I already know that the voltage is generally about 13.8 volts but that's about it.
I want to know how durable my input cicuitry has to be.
Any help would be appreciated.

Also what guidelines do I have to follow so I don't wreak havoc on the system. I don't want to pay $1000 for an SAE book.

 

[jons999]

Actually if the alternator is in good shape the voltage at the battery can reach 14.5VDC. The battery is supposed to act as a diode and regulator so i don't think you would get too many voltage spikes, most of the ecu's in the car are pretty fragile. Why not hook up an ocilloscope to your cars power outlet and drive around for a while? Some of the portable battery powered scopes have a feature which will automatically record the highest and lowest readings.

-Jon

 

[GregLocock]

There's a section in the Bosch blue book that details this, but for a non safety related item you need to design for transients of the order of +35V for 400 ms if the battery lead falls off, and switching transients of 25 V from accessories. System voltage during starting should lie between -3 (!) and 12 V. The latter is obviously a bit daft - I think the EEC etc have to work down to 8V.

It is much more complicated than this, of course if you need to get certification or if the system is in any way important. Cheers

Greg Locock

 

[RomanM]

Thanks for the information.

I have some posts in the electrical engineering forum and some responses were saying that I have to worry about +/-150V but they didn't say for how long.

Some responses were saying that I have to worry about 1500V. Thats a tough spike.

Roman

 

[RomanM]

I just got this from one of the other posts. It is what I was looking for:

http://www.schaffner.com/index.asp?menu=emclib&pagemenu=homepage&scopy=wallchart