I did a simulation. There was a glitch on one output if the relays close faster than they open -- which is often the case, particularly with DC relays snubbed with diodes.
The minor modification fixes that without requiring any more relays. Relay count now is:
If your relay coils aren't the same voltage as your load, then you may need to add a couple of SPST load relays.
This was fun. I haven't designed relay logic for decades!
Hello Don,
And now on to tube logic :-)
Cross-coupled 6146's comprising Eccles-Jordan flops -- yeah!
Why use 3 relays when one can put together a microcontroller, write and debug software, do signal conditioning of input, add relay drivers and output relays or load switches, find a power supply, and put it all in a box -- or buy a PLC, hook that up and program it with (ta dahhh) RELAY LADDER LOGIC?
I see some elegance in a rugged 2-bit state machine with a speed of ...uh...Hertz, that goes clackity clack and does the job, and can be built in an hour with 3 relays, some wire, a bag of crimp terminals and a crimper.
Hello Don,
Don't forget that can of contact spray ;-)
How about a one-shot? :-)
What's the delay mechanism? Capacitor,or just actuation delay time of one or more relays?
Hello Don,
The one in our heat pump had a transistor, some resistors and an electrolytic (which, of course, failed after 10 years or so).
The weirdest relay one-shot I ever saw had a cam that was lifted onto a notched wheel. Upon triggering it would start a little gearmotor. Rat-tat-tat-rrrrrrrrrrrrrrr-KLUNK.
You can still find similar schemes in washing machine timers. Those are probably "the" epitome of electromechanical control.
Capacitor.
Nah, in them days they were called condenser :-)
Ok - no takers. Here it is: relay one-shot (view in courier font)
And Tweakers! don't forget your contact tweakers!
I used to do SxS maintenance... 8-)
Charlie
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