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Turn Circuit On/Off With Momentary Contact

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martianman

New Member
Hello All,
I want to turn a circuit on and off using a momentary contact switch. I have a 4011 NAND Gate and and CD4027BE flip flop but every circuit diagram I've found doesn't do what I want. I'm using a 5v and 500mA power source. Any help is much appreciated! :)

P.S. I only want to use 1 switch. I found a circuit that used 2 bits with 2 switches using a 4011 NAND Gate: one set and one reset. This is not what I want.
 

ericgibbs

Well-Known Member
Most Helpful Member
Hello All,
I want to turn a circuit on and off using a momentary contact switch. I have a 4011 NAND Gate and and CD4027BE flip flop but every circuit diagram I've found doesn't do what I want. I'm using a 5v and 500mA power source. Any help is much appreciated! :)

P.S. I only want to use 1 switch. I found a circuit that used 2 bits with 2 switches using a 4011 NAND Gate: one set and one reset. This is not what I want.
hi,
For a 4027 this circuit will toggle the output for each clock input.
 

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martianman

New Member
Hi Eric,
I tried out your circuit in a few different ways and I couldn't figure out how to work it correctly. Let me give an example to make this easier for me. I want to use a 4027 or 4011 IC with one momentary contact switch to turn on and off an LED with one push. :)
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi Eric,
I tried out your circuit in a few different ways and I couldn't figure out how to work it correctly. Let me give an example to make this easier for me. I want to use a 4027 or 4011 IC with one momentary contact switch to turn on and off an LED with one push. :)
hi,
Look at this dwg, it does work.

If your push switch is 'noisy' [contact bounce produces multilple inputs]
you will have to use a debounce circuit for the clock.

What type of switch is it.?
 

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martianman

New Member
Ok I tried the second diagram you gave me Eric; that one didn't work for me either. Maybe I'm just hooking it up wrong... Could you give me a diagram with the pin names and pin numbers? I'm extremely confused here...
 

hdc090360

Member
Debounce

Using a momentary contact switch in Eric's circuit is always dodgy.

They normally produce a stream of pulses "switch bounce" and your output will be random depending on whether you get an odd or even number of bounces big enough to toggle the flip-flop.

Try putting a cap (1-10µF) across the switch or a debounce circuit using your 4011 chip.

debounce.JPG
 

ericgibbs

Well-Known Member
Most Helpful Member
Ok I tried the second diagram you gave me Eric; that one didn't work for me either. Maybe I'm just hooking it up wrong... Could you give me a diagram with the pin names and pin numbers? I'm extremely confused here...
hi,
Post your circuit diagram, lets see how you have the 4027 configured.:)

Note what I said about a 'noisy' push switch, debounce will be required.
Do you have a 4093 or 40106 ic on the bench.?? or any Schmitt type ic.?
 

ericgibbs

Well-Known Member
Most Helpful Member
Using a momentary contact switch in Eric's circuit is always dodgy.

They normally produce a stream of pulses "switch bounce" and your output will be random depending on whether you get an odd or even number of bounces big enough to toggle the flip-flop.

Try putting a cap (1-10µF) across the switch or a debounce circuit using your 4011 chip.

View attachment 31766
hi hdc,
Your circuit works fine with a change over switch, not with a simple push to close switch.

I would guess if the OP has a change over switch he wouldnt need any logic ic's.:)
 
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