[owhite]

Hey gang,

I would like to get ttl logic to toggle back and forth from high to low by pushing on a momentary contact pushbutton.

any suggestions for a circuit?

Owen

[pminmo]

Do you mean you want a logic level oscillator to start on the pulsh of a button?

Phil

[Al_The_Man]

Owen, Do you have a 7474? If I recall from my ttl days wire the PB to the Clock, connect /Q (Q bar out) back to the D input and use the Q output. If I remember correctly this will toggle the output every pulse.
I will have to dig out my old notes, unless someone has a better idea.
Al
BTW tie the clear and set high for normal operation.

[owhite]

Originally posted by pminmo
Do you mean you want a logic level oscillator to start on the pulsh of a button?

Phil

Phil, not an oscillator per se. I want to poke a momentary contact switch and have it send a circuit to high and have that circuit stay high. Then I'd like it to send the circuit to lo when it gets pushed again.

So far I've wired a 555 timer to debounce a push button switch, and now I'm looking for it to flip-flop a ttl circuit.

owen

[pminmo]

one more question, is the push button double throw? i.e. has normally open and normally closed contacs? The reason I ask is if it has both contacts you can do the dbounce with one half a flip flop.

Phil

[owhite]

Originally posted by pminmo
one more question, is the push button double throw? i.e. has normally open and normally closed contacs? The reason I ask is if it has both contacts you can do the dbounce with one half a flip flop.

Phil

single pole.

[Al_The_Man]

This one has worked for me, it has a 7404 debounce circuit into the 7474 dual D flip-flop.
Al
Oops I hope I can make the File a bit bigger!

[owhite]

Hoo boy.

I'm laughing out loud here because I'm really anxious to get a circuit and I clicked on yours and got this unreadable picture.

Al, could you be kind enough to try to post again, or just send it to [email protected]

thank much :-)

owen

[ESjaavik]

I'm glad to see someone still does it this way.
Give the problem to a student today, and there is a good chance he would come up with a PC Pentium4 3GHz w. 1GB RAM and a VB program to solve your problem. :-)

[owhite]

Al,

just to follow up, the circuit worked great. I went with using a 555 for the debouncing part because that's what I had on hand. The circuit is included here...

owen

[Al_The_Man]

Owen, Glad it worked, I date back to when we had to do this at one time with discrete components, that was a challenge!. Hail the IC.
Al

[owhite]

Al,

I think maybe we were separated at birth.

remember when it wasnt possible to go to the net and get a data sheet on chip?

because there wasnt a net...

or computers...

or chips. :-)

owen

[davesaudio]

dunno, looks too hitech to me

[owhite]

yeah I saw that one on the net. I couldnt go with the transistor approach because I'm only operating at 5 volt levels. good to include here if anyone searching this site later on.

owen