In <199710271825.KAA22493@unix.infoserve.net>, Ross MacPherson wrote:
>The lamp dimmers internals are designed to work with household AC supply. A
>similar circuit suitable for the dash lights could be put together easily
>(and cheaply) by the electronicly skilled for only a few bucks. Because the
>car's supply is DC an SCR must be used instead of a Triac. This bares
>looking into.
Well, not quite. The reason that house-type dimmers can be made
so cheaply is due to the use of AC. Neither triacs nor SCRs work with
DC, unless it is pulsating DC. To make this kind of dimmer for
your dash you need a timing circuit, power switchers, SCR and a gating
circuit. It would be efficient (fairly low heat) but complex. I just
jumper my dash dimmer out of the circuit. The instruments are barely
legible in that case and I can't imagine wanting them lit more
dimly....
A. B. Bonds
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