On Monday 29 April 2002 09:24 am, 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.
>
> Todd
Also another idea, I think. About a year ago I saw a controller at
Radio Shack that was used for security/home lighting that was PC
controlled. If I am right I don't see why that couldn't be adapted
for a sprinkler system.
Bob S
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