On Monday 29 April 2002 09:24 L, you wrote:
> Radio Shack has a couple mini-handbooks that have a lot of simple sample
> circuits in them. A couple of transistor relay drivers and switches.
> You'll also need an 8 bit latch to catch and hold the value written to
> the parallel port. You'll have to work out all the loads backwards to
> make sure the relay can handle the solenoid, the transitor can drive the
> relay and that the transistor ciruit doesn't over draw the latch, but
> hey that's the fun of hardware. With that you would have 8 on/off
> devices. If that isn't enough, you could add a flip-flop and a couple
> And gates to make an addressing scheme where the 8th bit is a
> solenoid/address indicator and the lower 7 bits are solenoid or address
> indicators. Then you just clone the circuit with minor And gate changes
> for each address of 7 solenoids. If you do more than 2 or 3? of those,
> you'll need an 8 bit buffer so the latches don't over draw the parallel
> port. I would advise going and getting an add on printer board, they
> are cheap, just incase you blow up your printer interface.
>
I have done a lot of this sort of thing over the years, this is the most fun
part from my perspective, the part that I can see work, make it flash,
buzz or ring.. Actually 8 bits should give me more than enough addresses
for what I need, and like you say, parallel cards are cheap I can put in
more of them. Building a control board should not be that big of a deal
either.
-- Chuck Hast KP4DJT kp4djt@tampabay.rr.com To paraphrase my flight instructor; "the only dumb question is the one you DID NOT ask resulting in my going out and having to identify your bits and pieces in the midst of torn and twisted metal."
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