SR latch

[duncan webster 1Participant @duncanwebster1]

I want to make a circuit with 2 switches such that one switch turns the output on, and the second turns it off. A square wave output. Once it's on, switch 1 should have no further effect, similarly switch 2 shouldn't have any effect once its turned off. This is easy enough, if that's all I wanted I'd use a couple of NAND gates, but I then want a second square wave at half frequency. What I've come up with is to use a 4013 dual d type flip flop, attach the switches to the set and reset of one with data and clock gounded and then use one of the outputs to clock the second flip flop which would have Q- connected to Data and set/reset grounded. Is this likely to work? I'll use FETs to get some output capability. The 4013 has the advantage that I've got one, and it's not too fussy about voltage. I've tried to post the schematic

Edited By duncan webster on 22/03/2018 05:23:57

Edited By duncan webster on 22/03/2018 05:26:46

[duncan webster 1Participant @duncanwebster1]

[Joseph Noci 1Participant @josephnoci1]

Hi Duncan. That will work fine. Just connect the unused inputs to GND or Vcc ( your supply voltage), ie, the first D type CLK and D input and the second D type ( the divide by two) R and S inputs. CMOS inputs left floating cause lots of problems…Also, add a 1uf and a 0.1uf capacitor across supply and ground, close to the device supply pins..

Happy switching.

Joe

[Joseph Noci 1Participant @josephnoci1]

Ducan, sorry, Brain not in gear…

The second D type R and S inputs must be connected to GND, NOT Vcc….Connected to Vcc will just set the Q output permanently..

In general, I connect unused inputs to GND..

Joe

[duncan webster 1Participant @duncanwebster1]

Thanks Joseph, as you can se by the time of my post, it was keeping me awake!

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