Re: Lighting questions

["Mark L. Chang" <mchang@ece.nwu.edu>]

On Sat, 8 Aug 1998, Huw Powell wrote:

> > Hella suggests relays with resistors and diodes on the control circuit
> > to avoid voltage spikes up to 500 volts produced by the relay closing.
> > I noticed the resistor and diode are on the control side.  So now my
> > relays will blow my brittle headlight switch, I can't win! ;)
> 
> If that's happening, what about all the other relays in the car?  That
> "spike" must be very short lived, generated by the relays coil.  Not
> many electrons...

In testing relays while debugging some of our transformer designs at my
father's company, we came across a similar situation.  Looks like a
inductive kick-back possibly from the relay coils -- but, what we saw was
a current spike in the neighborhood of 3x to 10x rated latching current --
but we weren't looking for anything else.  Blew out our circuit breakers
too often!  Strange ... YMMV.

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