dual d flip flop, oscillator

[henrymonkey]

have dual d cmos ff, would like to build a 1 hz square wave oscillator, waiting for 555 to come in mail, wanting to keep beard boarding till mail man come

 

[crutschow]

Why do you need the FF if you are getting a 555 to generate the frequency? Do you need an exact 50% duty-cycle? If so then just connect the /Q output to the D input of the FF to form a toggle FF. Then you feed a 2Hz signal from the 555 to the Clock input of the FF to generate a 1Hz square-wave with 50% duty-cycle.

 

[henrymonkey]

thank you. im building a project and realized I don't have any more 555. just need a square wave generator to test it on bread board . the 555 I ordered wont be here till Monday, I tried a series of inverters with a rc constant but don't work guess it isn't a good enuf square wave. just wanting a generator with what I have on hand till I get my package.. I have quad nand and ex or, also op amp . maybe I should just take beark and wait till mail runs on Monday I have 10daul d flipflops on hand

 

[MrAl]

Hi,

You can make an RC oscillator out of the NAND gates. Use one or two of them as an inverter by connecting the two inputs together. Make an RC oscillator and use one as output butter. Drive the FF with that you'll get a 50 percent duty cycle out .
What frequency do you need, anything specific?

 

[henrymonkey]

thank you, I can see that. im looking for about 1 or 2 hz, slow enough to be able to see the operations for now to help work out bugs, been using a debounced switch for one pulse at a time but as circuit grows it is too much to keep pushing button...when finished will clock about 10khz. appreciate your reply..

 

[MrAl]

Hi,

For that slow speed i think a 555 would work better, or an inverter type RC oscillator with a divide down counter string.
I am suggesting these things based on what i think you have available, but i cant be sure what parts you already have unless you list them all here, and if you care to do that i'll try to use those parts only.

 

[henrymonkey]

I have 10 cmos 4013 dual d flipflops, quad op amp 33174p,4011 quad nand, 4049 hex inverter,cd4017 decade counter,cd4018 divide by n counter, and most all discrete components also 10 npn transistors, 4023 3 input nand,4066 quad switch, think with these maybe I can fashion a low speed clock.

 

[MrAl]

Hi,

I think you can use your op amp for this circuit. You can vary the cap and/or R5 to change the frequency.

Using the 4049 inverter you might use the cap and resistor alone.

In any case you might want to use a FF on the output to square up the wave and make it 50 percent duty cycle.

 

[alec_t]

.... or you could try this:

 

[MrAl]

.... or you could try this:
View attachment 85467

Hi,

That's nice, but would you seriously use two capacitors and two resistors and two diodes and a flip flop rather than one cap and one resistor and either a single NAND gate, NOR gate, or inverter, or even single comparator or op amp?

 

[alec_t]

would you seriously use two capacitors and two resistors and two diodes and a flip flop

Personally, I wouldn't. But the OP wanted to use a D-flop. The thread title gives a bit of a clue

 

[henrymonkey]

thank you for all your input,, I made the one op amp changed the 10 uf to a 1uf and gated the out through an inverter on 4049, 2working super.... just right speed for me to visualize the functions and adjust gating accordingly.. a simple but effective solution, very much appreciated!!

 

[MrAl]

Personally, I wouldn't. But the OP wanted to use a D-flop. The thread title gives a bit of a clue

Hi,

Oh yes that makes sense now. I was wondering about that