Re: coolant pump control questions

Hi Mark,

Try tying one side of the relay to +5, and the other to pin 1. Parallel
port pins want to "sink" current, some can do both, but if not, as in
your configuration, the pin will not be able to "source" enough
current.

You might also search the past postings (yeah, I know there are a lot of
'em) for additional discussions on this topic.

Solid state relays (SSS) can be driven this way effectively. I love my
spindle power control (Sherline)!

HTH

Alan KM6VV


"markpowerplus " wrote:

>
> Yes , the problem I have is the control side of things, I don't know
> the range of the PC . By "switching" on the coolant in the software I
> get a 5 volt reading on pin 1 of the parallel port but it will not
> switch the relay which is a 5 volt 10 ma. When I connect the relay to
> pin 1 and the other side to earth the volts drop off to almost zero I
> am guessing here at saying there is not enough current? this is the
> smallest rated relay I could find (it is a reed relay) I could not
> find a solid state relay in 5 volts.
> help please!!!!!!!!
> thanks
> Mark