Yes, this chip is just transistor drivers, so it doesn't
require power.  The V+ pin goes to the + power of the motor
supply, and connects reverse diodes to the transistors.
Works great on the parallel port.  I've been doing a lot
with steppers lately, so feel free to ask anything..  2064
is another good chip, only good for 1 motor but handles 1.5A
(I think, could be just 1 A) vs the 2803's ~.5 A.  Actually
the 2803 seems to stand up ok at 1A, but runs hot and won't
last forever like that..
  Could send you some very simple pic and PC code if you
like..
Alan


Dave Vandenberg wrote:
>
> Will a ULN 2803 (8 darlington drivers) protect its inputs from back-EMF?
> In the case of a PIC driving a 2803 which drives the stepper motor coils,
> is there any danger of hurting the pic?
>
> I have mounted 2 5-wire stepper motors on a chassis (steering by
> differential drive).
> 4 PIC pins will drive both motors, with 2 XORs and 4 Inverters to derive the
> other signals for bi-phase (uni-polar) drive (0011, 0110, 1100, 1001) from
> (00,01,10,11).
> I will be trying the motors out with my parallel port first, to get the hang
> of them.
>
> Will any spikes get back to the PIC?
> Should I stick a 0.1uF or <what value> uF cap on each of the 4 PIC pins?
> Would the values of capacitance required depend on the speed of the stepping
> motors?
> Would opto-couplers be justified?
> What have I not considered?
> Any suggestions appreciated.
>
> </David_V>