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I need a certain button... Answered

I'm thinking of a project that requires a certain button. it needs to be low-profile, and be an on/off button (push on, push off) that doesn't pop up when it's off (like some buttons do so you can see if it's on or not). it just basically needs to be small (about the size of an LED, but in a square shape) and short (like a low-profile LED), and needs to be a push on, push off type button, like some flashlights have.

any search terms might help (like I know momentary switch, but I don't know what a.... well, non-momentary switch would be called). I also need a lot of them cheap.

I'm kind of crossing my fingers as to this actually existing....


I think the word you are looking for is "latching", but it refers to a circuit rather than a switch. A latching circuit and a SPST momentary push button work together to do the action you describe, i.e. push the button once and the device turns on. Pushing the button again, after some small amount of time, turns the device off.

By the way, for this trick to work there has to be some small small circuit that is always on. It is the job of this circuit to wait patiently for the button press, and then turn everything else on. However this circuit can be something that uses so little power, that for practical purposes, the device is essentially "off". For those who like to be pedantic, the phrase "sleeping" or "sleep mode", is a better description.

You can make such a circuit with something as simple as a single flip-flop ic, and maybe a few external components to add some hysteresis to it.  Reply if you are interested in more details on how to build this circuit. 

If you are looking for such a circuit in module form, it may exist somewhere, being sold by someone.

The picture of the momentary switches came from here:

the only problem with that is that I'm planning on making a big display that is essentially a checkerboard of lights and switches; the light is controlled by the switch next to it.. you run your finger over everything and you kind of draw with light.

Right.  You want a whole N-by-N array of these things.  

I think the traditional  way of doing such things is to use a microcontroller to sort of scan through an array of LEDs, briefly turning (or not turning) each one on, and doing it so quickly that each individual LED looks to the eye like it is turned completely on or off.

In a similar way you can also scan through an array of SPST buttons, to determine which one(s) is(are) being pressed.

And if you were really clever, you could maybe figure out a way to sort of merge the switch and the LED into the same element, e.g. by putting a (normally open) switch and LED in parallel.  That way you could use less microcontroller pins to do the same task.

Of course this microcontroller approach assumes that you are actually making things cheaper, on a cost per pixel element basis.  I mean cheaper than using a single flip-flop, or whatever, for each pixel.

 Instructables has a number of examples of microcontroller based LED matrix displays, um here:

The usual sizes of these example projects are circa 8*8=64 LEDs.

Also you've got the additional requirement of putting a button on each LED.

Good point. Using electronics rather than mechanics to obtain the latching behavior may be cheaper and gives you more switches to choose from. One caveat: When taking input from switches to logic circuits, be sure to debounce the switch; searching on that word will find details.

Sorry about the lack of picture, but the uploader is giving me difficulties today:

"Could not upload file 'Tactile_switches.jpg'. Please try again as it may simply have been corrupted in transit."

how about this button? http://parts.digikey.com/1/parts/961837-switch-pb-square-wht-mom-spst-no-d6-c-00.html i think what you want is a SPST, single pole single throw push button. single pole indicates the number of circuits for example a light switch controls one circuit (it connects two separated wires, one circuit) and single throw simply indicates the number of positions it can be in for example a button that returns to the same position it was in before it was pressed and a light switch would be a SPDT single pole double throw (two positions). so there you have it, decide how many poles you need and you indicated you only want one throw so it would be **ST square pushbutton. i think this is what is in flashlights by the way http://www.allelectronics.com/make-a-store/item/PB-217/SPST-TACTILE-PUSHBUTTON/1.html . and wikipedia has a good article on switches, just google "switch"

It probably exists, but finding it is going to involve a heck of a lot of searching through catalogs and/or contacting suppliers, and you may have trouble buying it in quantities less than 1,000. One example of a good place to look:
(Many other good suppliers exist; this is just the first one that came to mind.)

You may have to track down and buy the square switch-caps separately.