🚀 go-pugleaf

In article <1395@crash.CTS.COM> rpluth@pnet01.CTS.COM (Ron Pluth) writes:
>
>    I have a couple questions about TTL logic that I hope can be
>answered here...
>
>    1.  What's the easiest way to go about interfacing a TTL
>output (from, say, a standard S or LS AND gate) to a relay, for
>controlling anything from automobile (12VDC) to house (120VAC)
>environments?  These are two *different* situations.   I'm look
>ing for hardware that can be easily picked up at Radio Shack
>(gasp!)... if anyone would even happen to know part numbers from
>such equipment, this would also be great.

Well, it all depends on how much currentthe coil in the relay needs to
activate. I'll assume that your digital output is around 5 volts, and
that your relay coil needs to support at least 3 amps. If you can, use
relay (Cat. # 275-214 - $4.69). Then, you need some sort of transistor
that will support (E) 5 / (R) 150 = (I) 33.3 Ma. The transistor doesn't
have to be very powerful in terms of wattage, so we'll use the NPN transistor
(Cat. # 276-2030 - $.79). Now, connect the collector at +12V. Connect the
emitter to one of the coil leads on the relay. Connect the remaining lead
to ground. Now, connect the base to the output wire of your digital logic
circuit. You can now figure out how to wire the rest of the relay up yourself.
You're looking at about 5 bucks total, but you can cheapen the price if you
need less than 3 Amps. If you don't need that much current, use a smaller
comparable one - There shouldn't be any problem in current handling in the
transistor.

-->Chris
..tektronix!reed!percival!bucket!chrisb