Cmos bistable momentary push button help

diy didi · Jun 16, 2019

Hi guys.
I have a need for a simple Cmos IC type bistable circuit.
My requirements are:
Must be able to work with 12V supply
Must have two output pins that go “hi”. If one goes HI, the other toggles LOW, and visa versa.

I have had a look at the 555 timer but it only has one output pin.
Any ideas would be much appreciated.
Thank you.

crutschow · Jun 16, 2019

A 555 will work as a set/reset bistable circuit, not readily as a toggle flip-flop.

Here's a push-button controlled, bistable circuit using a CMOS CD4013 D-FlipFlop that includes a debounce function (R1-C2) for a mechanical push-button.
The Out and Not_Out are complementary outputs.
It can operate from a 3V to 15V supply.

diy didi · Jun 17, 2019

crutschow said:
A 555 will work as a set/reset bistable circuit not readily as a toggle flip-flop.

Here's a push-button controlled, bistable circuit using a CMOS CD4013 D-FlipFlop that includes a debounce function (R1-C2) for a mechanical push-button.
The Out and Not_Out are complementary outputs.
It can operate from a 3V to 15V supply.

View attachment 118927

Thank you soo much. Appreciate it.

diy didi · Jun 19, 2019

crutschow said:
A 555 will work as a set/reset bistable circuit, not readily as a toggle flip-flop.

Here's a push-button controlled, bistable circuit using a CMOS CD4013 D-FlipFlop that includes a debounce function (R1-C2) for a mechanical push-button.
The Out and Not_Out are complementary outputs.
It can operate from a 3V to 15V supply.

View attachment 118927

What is the function of R1 and c2?

audioguru · Jun 19, 2019

R1 and C2 prevent the pushbutton contact bouncing from causing many alternations of this circuit when you push the button only one time.
You did not mention how much output current you need then the CD3013 might be too weak.

gophert · Jun 19, 2019

Minor typo...

audioguru said:
You did not mention how much output current you need then the ~~CD3013~~ CD4013 might be too weak.

crutschow · Jun 19, 2019

diy didi said:
What is the function of R1 and c2?

R1 and C2 delay the change in state of the D input (which occurs at about 1/2 the supply voltage) until any switch bounces has passed (delay time about 0.7RC).
Thus the flip-flop can only change state once, no matter how many switch-bounce clock pulses occur within that delay time.
Once past that delay time, the D input goes to the opposite state, and the FF can again change states from an input clock pulse.

Make sense?

diy didi · Jun 19, 2019

So basically a debounce help circuit?

crutschow · Jun 19, 2019

diy didi said:
So basically a debounce help circuit?

What do you mean "help".
It's normally just called a "debounce circuit".
It inhibits the circuit from responding to the bounce signals from a mechanical switch.

Cmos bistable momentary push button help

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Cmos bistable momentary push button help

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