--- In
68HC12@..., "Vernon Lermond" <VERNON9998@...> wrote:
> I use a ULN2803A darlington array to drive relays. The chip has
> surpressor diodes to absorb the energy in the relay magnetic field
> when it is shut off and will sink 500ma per darlington. The
> processor should not be used to drive relays directly as the current
> requirement is likely to exceed the output rating of the chip and
> the "spike" when the relay is shut off may damage the processor
> output or cause a "noise crash" - and require a reset.
In fact the Dragon12 has an "application corner" where there is a
circuit (without the parts stuffed) for a relay driven by NPN
transistor (i.e. 2N2222). It accomodates a 1K on the gate and 1N4004
to protect the silicon, but who knows whether b_scheibe is using this
circuit? It would not likely be that same relay because... how much
power might one supply to power a "heater"?
