I know there are many ways to do this, but I'm looking for the easiest setup, not necessarily the cheapest.

I need to build a circuit in which a momentary switch alternates power between two 110v lamps. I believe I need to use a D flip-flop and have the output control a relay, but other than that I'm a little unsure. So, press the momentary open switch once, lamp 1 illuminates, press again, lamp 2 comes on. Simple as that.

I don't want to use any microcontrollers. I want to see if I can do this with minimal components. In this case the relays are just operating like transistors, at least from what I can tell.

Is there a simple way to use a spdt relay and just use the flip flop to toggle relay positions? What specific relays should I be looking for? (solid state or mechanical?) And is there a simple flip-flop IC that would work well for this?

I've considered just using a SPST high power switch, but for this project I need to use a specific arcade-style momentary pushbutton and therefore looking for a workaround.

I have to have it built within the week, I really appreciate anyone's help. Thank you, and I apologize if this question comes up a lot.

  • \$\begingroup\$ Also, in this case I would be using an AC relay, right? not DC? \$\endgroup\$ May 15, 2018 at 22:01

1 Answer 1


A bi-stable latching relay would be a simple solution.

enter image description here

Figure 1. Go to HomoFaciens and click "Start animation" to see how the pawl mechanism is advanced on every impulse of the relay coil.

No flip-flops, electronics or magic is required. Wire your button between the power-supply and the coil. Each impulse will change the state of the contact.

Imgur doesn't seem to like animated gifs.

  • \$\begingroup\$ +1 for sharing that cool animation web link. \$\endgroup\$
    – AlmostDone
    May 15, 2018 at 23:53

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