Using one push button to enable and disable a LED permanently without uC

Thread Starter

dman92

Joined Apr 30, 2021
4
Hello,

I'm searching for an IC able to keeping enabled or disabled multiple LEDs with a push-button without a uC, but I haven't found anything.

Thanks!!

I don't want a mechanical button.
 

LesJones

Joined Jan 8, 2017
3,570
You will need to define what you require more precisely. Do all the LEDs go on and off together? Is it just to tooggle between on and off or is it a more complex requirement ? Does it have to remember the state when power is removed from the circuit ?
Will a push on / push off push button not meet your requirement ?

Les.
 

Thread Starter

dman92

Joined Apr 30, 2021
4
Hello,

First thanks for your answer. The only purpose is to keep the LEDs on or off. Doesn't matter the state when the power is removed.

I need to use a simple pushbutton, not a switch o mechanical push button.

EDIT: The push-button will mount on a PCB.

Some like this:
1629113708943.png
 

AnalogKid

Joined Aug 1, 2013
9,471
I need to use a simple pushbutton, not a switch o mechanical push button.
First, some clarity. A "pushbutton" almost always *is* a mechanical switch.

One way to do this is with an alternate-action switch- push once and and release, and the circuit stays on; push again and release, and the circuit stays off; repeat - but I suspect that this is what your aree trying to say that you do not want. If so, then what you want is a toggle flipflop circuit. this can be formed with two transistors, or two logic gates, or one D-type flipflop chip plus some resistors and capacitors. There are many schematics on the innergoogle. Depending on the circuit, you can get two or three independent circuits with only one very low cost chip.

Here is a circuit from Crutschow, a regular contributor on this forum. To drive LEDs, add a small power MOSFET to the output. Another approach is to find and buy a specialty IC specifically designed to be an LED switch, like the ones used in flashlights.

ak

Toggle-Dff.png
 
Last edited:

LesJones

Joined Jan 8, 2017
3,570
Out of interest while looking for push on push off (Latching.) push buttons on Farnell's website I found this IC on the page for push button switches. It seems to do what the TS requested but to my mind a latching push button is a better solution. This IC would probably require a transistor or mosfet to drive the LEDs

Edit. I had missed the but about excluding a mechanical switch. I have seen a Hall effect push button (That looked like a V3 micro switch.) but even that has a magnet that moves in relation to the Hall sensor. A capacitive switch is the only thing I can think of that would not be excluded.

Les.
 
Last edited:

Reloadron

Joined Jan 15, 2015
6,203
They make simple push button switches to do that. Push once and it's On, push again and it's Off, all mechanically done. I have some Leviton manufacture sitting here but Hillman and Carling also make them. If you want to go with electronic The Circuit from Crutschow in post #5will do and includes debounce. The CD4013 is an old classic D flip flop. The link by Les Jones is a newer version and also takes care of switch debounce. So you have purely mechanical and simple or a few electronic flavors to work with. The rest depends on your load current.

Ron
 

metermannd

Joined Oct 25, 2020
232
I concur on using a latching pushbutton.

I ordered a pushbutton for a board I put together recently and I didn't look close enough and realized too late I'd ordered a latching pushbutton rather than the momentary I wanted. The switch I wound up with is part CW181-ND at Digikey.
 

AnalogKid

Joined Aug 1, 2013
9,471
In his own way, I think the (invisible) TS was clear about using a SPST momentary pushbutton switch, with a circuit of some kind to provide debounced, alternate-action functionality.

ak
 

crutschow

Joined Mar 14, 2008
28,155
Here's a two MOSFET version of the circuit in post #7:
They both have the advantage of using no ICs and not requiring an added transistor to drive the LEDs.
MOSFET M2 just needs to be sized to carry the total LED current.
If the supply voltage is less than 10V then M2 should be a logic-level type [Vgs(th) max ≤2v].

1629210918485.png
 

Ian0

Joined Aug 7, 2020
3,739
Here's a two MOSFET version of the circuit in post #7:
They both have the advantage of using no ICs and not requiring an added transistor to drive the LEDs.
MOSFET M2 just needs to be sized to carry the total LED current.
If the supply voltage is less than 10V then M2 should be a logic-level type [Vgs(th) max ≤2v].

View attachment 245829
Not only is it a 2-MOSFET version of the circuit in post #7, it is also a two-MOSFET version of the two-inverter circuit! (Post #13)
 

crutschow

Joined Mar 14, 2008
28,155
Not only is it a 2-MOSFET version of the circuit in post #7, it is also a two-MOSFET version of the two-inverter circuit! (Post #13)
Yes, it basically is.
The choice between the posted circuits thus appears depend mostly on whether you want to use a design with an IC (which requires a buffer transistor) or one that just uses transistors.
 
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