I apologize if this has been asked before but the answers I found are all over the top for this simple latching application.

I'm looking for a very compact solution:
1) 4.5 volt dc, 3 stacked hearing-aid like batteries.
2) Single 2.xV LED load
3) Push button actuation; push once & release = on; push once again & release = off
4) Soft latching; no power consumption when off.

I'd think something like this should be no more than 4-5 component, not counting the batteries, switch, and led.

A nice to have would be a single chip based solution with (or w/o) switch de-bounce.

I'm somewhat amazed these are not a dime a dozen solutions out there to be found.

Any suggestions?

Much thanks.

EDIT 4.5V, 3 stacked hearing aid batteries offers meany more LED options @ ~ 20mA. http://lednique.com/leds-and-colour/

Hoping to stick with a soft latch technology t minimize the switch physical footprint.

A resister and toggle button does not satisfy the requirement.

No programming required preferred.

  • \$\begingroup\$ Only infrared LEDs are 1.5 V, unless something has changed. You forgot to mention the current required. A part number and datasheet link for the LED would be nice. Hit the edit link ... \$\endgroup\$
    – Transistor
    Commented Apr 23, 2020 at 21:08
  • \$\begingroup\$ Single chip and compact could be: a 6 pins SOT package microprocessor. But that involved coding. Is programming within your scope? \$\endgroup\$
    – Huisman
    Commented Apr 23, 2020 at 21:13
  • \$\begingroup\$ Why not just a resistor and a toggle button? \$\endgroup\$ Commented Apr 23, 2020 at 21:56
  • \$\begingroup\$ You want what's known as a "press-twice" PB. They contain a mechanical ratchet that's rotated each time the button is pressed. They are used in flashlights, car audio, and elsewhere. Just look around. \$\endgroup\$
    – jonk
    Commented Apr 24, 2020 at 1:51
  • 1
    \$\begingroup\$ But what do you mean by "soft latch"? Can you point to an example of this kind of circuit? How do you know that is uses no (zero, none whatsoever) power? \$\endgroup\$ Commented Apr 25, 2020 at 15:05

1 Answer 1


Single pole, push-to-on / push-to-off micro switches are readily available.

  • \$\begingroup\$ Thanks for the reply. Can you find a link on something like DigiKey. Because googling "push-to-on / push-to-off micro switch" returns a bunch of false-positive and ambiguous hits \$\endgroup\$
    – Steve
    Commented Apr 26, 2020 at 15:27
  • \$\begingroup\$ "Push Button SPST"? A SPST as a push button instead of a toggle? \$\endgroup\$
    – Steve
    Commented Apr 26, 2020 at 15:30
  • \$\begingroup\$ Hi Steve, Please try 'Push-On Push-Off Micro Switch 18x12 mm'. \$\endgroup\$
    – vu2nan
    Commented Apr 27, 2020 at 4:01
  • \$\begingroup\$ Thank you, Steve. \$\endgroup\$
    – vu2nan
    Commented Jun 22, 2020 at 10:40

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