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Is there a way to circuit a power efficient toggle switch controlled by a SINGLE button so that absolutely no current from the power source is drawn at it's OFF state and hopefully but not exactly necessarily, minimal current is drawn on its ON state. So far I got this...

It consumes no power when OFF and when pressed the led turns ON. I couldn't figure out the turning off bit.

Also don't suggest me to use a button that mechanically toggles. I know that exists, but I don't want to use that.

Additionally I do not want to use normally-closed/double-throw buttons and normally-closed/double-throw relays (which means I only allow the normally-open version of these components). If your solution requires those component variants however, I wouldn't mind for you to post them.

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    \$\begingroup\$ Just use a mechanical "Push On/Push Off" switch. \$\endgroup\$
    – R Drast
    Apr 11, 2016 at 16:01
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    \$\begingroup\$ What about a step (or stepper) relay? Is that ruled out as well? Here: soselectronic.com/… ; You need the simplest of the configurations. \$\endgroup\$
    – Sredni Vashtar
    Apr 11, 2016 at 16:41
  • \$\begingroup\$ @RDrast I'm aware of that solution. But I don't want to use that, that's the challenge. \$\endgroup\$
    – Bradman175
    Apr 12, 2016 at 0:33
  • \$\begingroup\$ @SredniVashtar I would say it's ruled out because I want to be able to create something straight from my inventory, and that looks quite specific. \$\endgroup\$
    – Bradman175
    Apr 12, 2016 at 0:34

3 Answers 3

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You don't need two relay: -

enter image description here

The circuit above also gives you an "off" facility too. Make sure your LED is current limited.

You can also buy a latching relay: -

enter image description here

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  • \$\begingroup\$ The circuits you provided use two buttons. I only want one button to control both states. \$\endgroup\$
    – Bradman175
    Apr 11, 2016 at 13:35
  • \$\begingroup\$ You are right though in the fact I only need 1 relay in the unfinished circuit I provided. \$\endgroup\$
    – Bradman175
    Apr 11, 2016 at 13:57
  • \$\begingroup\$ Short out the "stop" button to remove its functionality. \$\endgroup\$
    – Andy aka
    Apr 11, 2016 at 14:05
  • \$\begingroup\$ The circuit I provided was UNFINISHED. I want something like a T-flip-flop not a SCR. \$\endgroup\$
    – Bradman175
    Apr 12, 2016 at 0:27
  • \$\begingroup\$ A single pushbutton is supposed to turn on and turn off the connection. \$\endgroup\$
    – Bradman175
    Apr 12, 2016 at 0:44
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What you want to do requires a 4-state asynchronous state machine. For example, a mechanical latching pushbutton implements the 4 states mechanically, in the various positions of its internal parts.

If you are restricting the solution to use non-latching, normally-open SPST switches and relays only, and consume zero power in the standby state, then it is impossible to construct the necessary state machine.

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Dave of EEVblog did an episode on a soft latch circuit that looks like it does what you want. You have to make the capacitor big enough that the circuit doesn't mistakenly oscillate back and forth if you press the button and end up holding it down a fraction of a second too long. Hope this solves your problem. Here's the link:

EEVblog #262 – World’s Simplest Soft Latching Power Switch Circuit

Schematic Circuit Diagram for EEVblog 262, Worlds Simplest Soft Latching Power Switch Circuit

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