spike protection in automotive applications???
spike protection in automotive applications???
(OP)
Hi guys, just want some help in providing surge protection to a circuit im designing for use in a car. The ciruit uses a pic controller so runs on 5v through a voltage regulator(L78S05CV). What i need is a cost effective choke/filter or another way of doing the job. Also will there be any problems when starting the engine as there is usually a drop in the current to the rest of the car?
Cheers for any help.
Fin
Cheers for any help.
Fin





RE: spike protection in automotive applications???
RE: spike protection in automotive applications???
RE: spike protection in automotive applications???
RE: spike protection in automotive applications???
RE: spike protection in automotive applications???
Thread67-98147
Thread67-94753
Thread240-98170
RE: spike protection in automotive applications???
When did you measure these spikes... during every start and/or stop, only during component failures like load dumps, etc.? Essentially, did you find these to be typical or once-in-a-blue-moon type of occurances?
RE: spike protection in automotive applications???
RE: spike protection in automotive applications???
- a forward series diode will eliminate the reverse spikes or connections.
- a current limiting device to control the overload inrush to the overvoltage protection device.
- an overvoltage protection device like a tranzorb. The wattage rating of the tranzorb is a function of the max current that the curent limiter will give during the energy spike. Set the voltage of the Vz high enough so that just the high spikes are absorbed, but within the regulator's range.
- LC filtering. Will also help keeping the juice (with the series diode) during crank-up. Watch if the capacitor has a max current surge rating. Many tantalums do.
- you may also want to fuse the line.
The protection circuits for an automotive application can jack up the component count and the product cost as well. It depends how serious your design is, meaning hobby or high volume. Balancing all these to have a good and cost competitive product is the engineer's job.
RE: spike protection in automotive applications???
RE: spike protection in automotive applications???
made easier. The regulator will work with 7V on its input.
Calculate a resistor that will give 5 volts of drop at the
maximum current your circuit will draw and place this in
series with the suppply.
Then a zener from regulator side of the resistor to
ground will limit the voltage.
This will limit the stress the zener endures and
maximize the transient voltage-duration product your
circuit will survive with.
Check your circuit for trouble with slowly rising power
supply though.
At one company I worked for they protected engine control
units with a 5W 27Volt zener across the power input.