I need to build a soft latching on-off-on switch that latch with momentary push buttons for use in on a 220v AC power line.
I mean a switch that have three momentary push buttons (2 buttons for on state and one for off state).
Is there a schematic for this?


  • \$\begingroup\$ Why two "On" buttons? Do you need to be able to distinguish which one was used? \$\endgroup\$ – Dave Tweed Oct 14 '13 at 14:45
  • \$\begingroup\$ @DaveTweed: two on buttons for two separated outputs; I actually need to activate two devices (both off or one of them on - selectable) - I just need to be able to use each of them to select output line ( like an SPDT switch) or turn off both; actually I need a soft latching version of three position on-off-on SPDT switch \$\endgroup\$ – RYN Oct 14 '13 at 14:54
  • \$\begingroup\$ what is soft latching? \$\endgroup\$ – Andy aka Oct 14 '13 at 15:06
  • \$\begingroup\$ It isn't clear what you mean by "soft latching" in this context. You can purchase three-position SPDT swiches that latch in neither "on" position, one "on" position or both "on" positions. What do you need that this doesn't cover? \$\endgroup\$ – Dave Tweed Oct 14 '13 at 15:31
  • \$\begingroup\$ Ah, I think I see ... you want the functionality of a three-position toggle switch, but you want to do it with momentary pushbuttons instead. I assume this means that if one device is on and someone pushes the other "on" button, the first device should turn off first. \$\endgroup\$ – Dave Tweed Oct 14 '13 at 15:50

Use simple relay logic. It will be simplest possible solution. If you get 220VAC relays, it can be made without additional power supply (sorry, the graphical symbols are not very good):


simulate this circuit – Schematic created using CircuitLab

  • \$\begingroup\$ That's close to what I was going to propose, but there are two problems: 1) It still uses mechanical switches, which the OP has ruled out, and more importantly, 2) It lacks the functionality of turning off Load1 when Load2 is turned on, and vice-versa. (You basically need a third set of N.C. contacts on each relay.) \$\endgroup\$ – Dave Tweed Oct 14 '13 at 21:49
  • \$\begingroup\$ Hm, as I understood the question, he needs 2 ON buttons in order to switch the loads on separately and one OFF to switch off both loads simultaneously. And also, he needed momentary push buttons. Exactly as I draw it. Let's wait for the asker to comment. \$\endgroup\$ – johnfound Oct 14 '13 at 22:11

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