How do i make this logic switch?

[AcousticBruce]

I would like to make a logic switch.

Lets say you push the switch once it starts a LED.
You push the same switch again and stops the LED.

How can I accomplish this with one push switch?

I have already successfully made a smiler circuit with 2 push switches. one switch turned on the LED the other turned it off. I figured you called this a logic switch... correct me if im wrong please.


EDIT ********************************************************

I have an aquarium that needs all the power heads to be shut off for ~15min during feeding time. So What I would like is a SIMPLE custom circuit that you can push a button and it cuts the AC for 15 min.

I understand how to make the timer portion of the circuit. I need a logic switch to control a Junction FET or a relay.

I was trying to do this without asking how to design the whole thing. So I just wanted the logic switch portion. I figured I can have in place of that led a high power transistor (or similar component). But a timer circuit would drive the logic switch to cut the power.

I posted this picture because this is the basic idea of what I am going to build. The difference is the timer will be strictly 15 minutes (possibly a potentiometer). Just one push of a button cuts the power and strarts a timer, when the timer is up the power is back on.


**broken link removed**



thanks
MikeBruce

 

[Roff]

**broken link removed**

 

[audioguru]

This discrete circuit does what you want.

 

[AcousticBruce]

**broken link removed**

Thanks there is some interesting circuits on there.

This discrete circuit does what you want.

Ill look this over thank you. It is quite a bit more complex than I thought it would be.

 

[audioguru]

The circuit with a logic chip is very simple and you can make 3 of the circuits from one cheap IC.

 

[Leftyretro]

I would like to make a logic switch without a IC.

Lets say you push the switch once it starts a LED.
You push the same switch again and stops the LED.

How can I accomplish this with one push switch?

I have already successfully made a smiler circuit with 2 push switches. one switch turned on the LED the other turned it off. I figured you called this a logic switch... correct me if im wrong please.


thanks
MikeBruce

And of course there are mechanical switches avalible that do that function, push once contacts close, push again contacts open. I think they are called alternate action.

Therefore no other other components required other then the LED and it's current limiting resistor.

Lefty

 

[saturn1bguy]

Lets say you push the switch once it starts a LED.
You push the same switch again and stops the LED.

How can I accomplish this with one push switch?

Must you use a circuit? Why not just a non-momentary pushbutton? Jameco P/N 164494.

EDIT: It looks like Lefty beat me to it...

 

[Mikebits]

The circuit with a logic chip is very simple and you can make 3 of the circuits from one cheap IC.

AG, you should write a circuit cookbook. Kinda like RS had a few decades ago.

 

[audioguru]

AG, you should write a circuit cookbook. Kinda like RS had a few decades ago.

Forrest Mimms is on one of these electronics chat forums lately.

 

[AcousticBruce]

Must you use a circuit?

It must be a circuit regardless if there is a perfect mechanical solution. Because I am in learning mode.


More info on what I am doing....

I have an aquarium that needs all the power heads to be shut off for ~15min during feeding time. So What I would like is a SIMPLE custom circuit that you can push a button and it cuts the AC for 15 min.

I was trying to do this without asking how to design the whole thing. So I just wanted the logic switch portion. I figured I can have in place of that led a high power transistor (or similar component). But a timer circuit would drive the logic switch to cut the power.

I posted this picture because this is the basic idea of what I am going to build. The difference is the timer will be strictly 15 minutes (possibly a potentiometer). Just one push of a button cuts the power and strarts a timer, when the timer is up the power is back on.


**broken link removed**

 

[fingaz]

Hi,

If it was me, I'd use a ne555 timer ic (monostable mode) and a relay to cut the AC power.
Have a look and see what you can find on google about the 555, they are relatively cheap and you would only need a few other components to build a suitable circuit.

Neil

 

[AcousticBruce]

fingaz If it was me, I'd use a ne555 timer ic...

I have been studying a 555 and it is probably a must for this design.

A relay or a high power junction FET is what I was thinking. But I want to drive these with a logic switch. When I start the timer I would like it to send a signal to the LOGIC SWITCH which sends a signal to the JFET and in ~15 min the LOGIC SWITCH will invert and no more power to the JFET, which allows for the 120V to flow freely.

I was thinking a Junction FET would be best. Do you agree?

AudioGuru The circuit with a logic chip is very simple and you can make 3 of the circuits from one cheap IC.

Yes i am thinking the IC will be best to use. As for the other "discreet" circuit you posted. I just did not get that to work. But do I really need that many transistors anyway for a Logic switch that just inverts from off to on?



thanks everyone for your patients
MikeBruce

 

[audioguru]

The logic circuit does more than just turn on and off. It latches the output until the button is pushed again then it changes direction and latches again like a flip-flop.

15 minutes is too long for a 555 timer. The timing capacitor must be a huge and expensive one, not a cheap little electrolytic type that has too much leakage current.
An oscillator/counter/timer like the CD4541 is suitable.

 

[fingaz]

The logic circuit does more than just turn on and off. It latches the output until the button is pushed again then it changes direction and latches again like a flip-flop.

15 minutes is too long for a 555 timer. The timing capacitor must be a huge and expensive one, not a cheap little electrolytic type that has too much leakage current.
An oscillator/counter/timer like the CD4541 is suitable.

Sorry to be argumentative, but here is an excerpt from the ne555 datasheet which can be found here: https://www.electro-tech-online.com/custompdfs/2008/11/555an.pdf

7. What is the longest time I can get out of the timer?
Answer: Times exceeding an hour are possible, but not always
practical. Large capacitors with low leakage specs are quite
expensive. It becomes cheaper to use a countdown scheme (see
Figure 15) at some point, dependent on required accuracy.
Normally 20 to 30 min. is the longest feasible time.

So it really depends on the accuracy required. If timing to within a minute is accurate enough, then the 555 can still be used.

Neil

 

[blueroomelectronics]

Here's a CD4060 circuit for an AC timer.
Electronics timer by CD4060