Circuit Protection on an automotive electronics application 2

[djroseman]

Hi,

I have a requirement to make a protection unit to prevent damage to our telematics system from large voltage and current spikes, both from the vehicle and attempted sabotage by operators.

The normal operating voltage is 24V, but it is possible to have up to 80V or more spikes. My current thinking is to use a clamp or crowbar circuit with inline fuses, which should pop instead of burning out the tracks. Any ideas on this? Also, what sort of current handling can I expect on 100thou PCB tracks in 1oz Cu?

Thanks

Dave Roseman

 

[Warpspeed]

Probably, until some rural mechanic connects a mains powered fast battery charger to it.

These usually consist of a transformer, rectifier, and (sometimes) a rudimentary filter choke. If the average dc charging voltage is something like 28 volts, the voltage peaks could in theory go as high as 28/.637 or 44 volts.

Voltage clamping the odd stray spike is trivial. Voltage clamping an alternator dump for several seconds is tolerable. But clamping sustained repetive voltage peaks, from a source that can supply possibly tens of continuous amps is a big ask.

 

[Comcokid]

I used to design electronics for industrial off road vehicles. One OEM had a spec that 24 volt systems be able to withstand 80 volts for 2 minutes. This is because at some minning sites the operators would jump a dead battery from battery power minning cart, and they were 80 volts. It gets hard to shunt or clamp this much overvoltage, so some designs just used a zener to trigger a transistor circuit to open-up the power to the device under overvoltage.

When operators have down equipment, they will use whatever they have at hand to get it running.