> I have some darlington arrays here they are ttl compatible so will
> they harm the board if i hook a led to each poll of the darlington and
> use the boards pins to turn them on and off
That should work fine, just watch what you intend to use for a power
supply, as that current has to be dissipated in the linear regulator.
If you are using a 5V regulated supply it should be OK, if you want to
get to the 500mA rated current the input voltage will have to be lower,
or the positive supply can use the input voltage supply.