> > A 2803 has bleeder diodes to the Vcc, which is the only function of the
> Vcc
> > pin. Don't forget to connect it, otherwise things will work normally
but
> > only for a short time. The bleeder diodes protect the 2803, the circuit
> > driving the 2803 won't notice any spikes.
>
> The motor windings should not be running from VCC, and returning those
> diodes to VCC will be potentially a very interesting experience. You
should
> return them to the motor supply voltage.
>
> Returned to VCC, all the spikes from motor coil switching are dumped onto
> your VCC line. Further, if your motor voltage is more than a diode drop
> higher than VCC, you will be running current from the motor supply onto
your
> VCC, which has serious consequences for any regulation you might be
trying
> to achieve on VCC.

But would that have any negative consequences when the motor's
Vcc is 12V and the PICs uses 5V derived from the 12V via a 7805?
At least I used this setup for some time without noticing any
problems. The impedance of my 12V is very low (nicads, big C).

Wouter.