How can I use a momentary switch (like a membrane switch) To control something? I want it to turn the device On or off by pressing the button. Ive tried latches, but it seems you need 2 Switches for the device to work.

 

You could also use either a J-K flip-flop or D-Latch flip-flop circuit to get the desired results. If memory serves me well, a similar post addressed this very same topic.

Try using the search function and search for those key-words, or the IC's 4013, 7474 (D-Latch) or 7476 (J-K)

Some Examples ... http://www.cpemma.co.uk/flipflop.html

 

You can do it with one switch and a JK or D type Flip Flop.

However, you need a bounce suppressor to eliminate contact bounce from the switch. Otherwise, the FF will toggle at every bounce and, when the bouncing has finished, be either in the set or reset state depending on whether there was an odd or even number of bounces.

Connect the switch to the bounce suppressor and the output of the BS to the Ck input of the FF. For a D type FF connect D to Q bar.

Do a search for "bounce" in this forum. There have been several circuits posted in the past including some by myself.

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Len

 

Try This Diagram I already built.Working fine.but it has about 1s (Propogation delay) delay.(output swtching Delay)

Attached Images

Latch.gif (5.7 KB, 59 views)

 

This circuit uses a momentary pushbutton. Push and it is on. Push again and it is off. Push again and it is on again, etc. It can drive a transistor or Mosfet for more output power.

Attached Images

Alternate-action.gif (3.6 KB, 71 views)

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Uncle $crooge

 

A very interesting, clever design,
from an old book on relay circuit design (probably 1951),
a toggle flip-flop, using only two relays, is shown in
attachment toggle1.png

Attached Images

toggle1.png (1.8 KB, 51 views)

 

This circuit should be a sticky somewhere. It is requested about once every 6 weeks!

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"Everything that is done in the world is done by hope." -Martin Luther
"There are two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle."-Albert Einstein

 

Interesting. I ran a simulation on that circuit using multisim, It oscillates when the switch is open, and when the switch closes (for 1 Moment in time-I used a momentary) it stops. If I press it again it doesnt change states.

ADD: Got it to do what I want. I used a D type FF used as a toggle FF.

http://www.doctronics.co.uk/4013.htm

 

The latching circuit with two inverters works fine. Multisim doesn't know if it is coming or going.

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Uncle $crooge

 

Audio, Are you sure?

I designed to attached circuit a year or 3 ago and found that the oscillator (which is similar to your latch) had ringing at each edge. I solved it by adding C4 at the input to IC1a.

Attached Images

Digital Dice_1.gif (12.2 KB, 32 views)

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Len

 

Hi Len,
You used the Classic Cmos Oscillator circuit but you used a Schmitt-trigger IC instead of a regular one. You could have used only a single Schmitt inverter instead.

Attached Images

Cmos Oscillators.PNG (16.3 KB, 25 views)

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Uncle $crooge

 

Yes, I know Audio, I have used the single one occasionally but, what I don't like about it is that it is always working in the active region and therefore needs more supply current than the 2 inverter one.

This is because the 2 Inv one causes the input voltage (ie. to the second Schmitt) to go above Vcc at the transition and decay to the lower threshold level where it switches regeneratively to the other state and so the input voltage goes negative and then decays to the upper threshold etc.

So there is less time spent in the active region, therefore less supply current.

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Len

 

Hi Len,
I made 3 LED Chaser projects. This one uses ordinary Cmos Schmitt trigger inverters in oscillators from a 6V battery that lasts "forever". I also have it made with 74HC Cmos Schmitt trigger inverters so it can operate from a 3V battery that drops to 2V. The current is very low.

Attached Images

6V LED Chaser schematic.JPG (91.6 KB, 35 views)

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Uncle $crooge

 

G'day Audio, That's interesting, I've never bothered to measure the supply current of the one Schmitt Oscillator nor look at the Schmitt data sheets (as far as supply current is concerned). So I assume that the Schmitts are designed to not consume excess current while the input is in the mid range.

Thanks for the info.

have a good Xmas

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Len