Try it yourself
Wire a three-way switch
Two switches, one light, either one controls it. It is the circuit that trips up more apprentices than anything else on a residential rough-in. Drag the wires, flip the levers, and see what your circuit actually does.
Drag from one terminal to another to run a wire. Click a wire to pull it out. Click either switch lever to flip it — the board is live the whole time, so you can watch the circuit as you build it.
- Breaker
- Closed
- Lamp
- Off
- Switch 1
- Down
- Switch 2
- Down
- Wires run
- 0
The idea
How a three-way actually works
There is no "on" and "off" position on a three-way switch. That is the whole trick, and it is why the diagram never quite makes sense until you have wired one.
The common screw
Each switch has one odd screw — darker than the others, usually black. That is the common. On the first switch it takes the incoming hot; on the second it feeds the switch leg out to the light. Those two commons are the two ends of the whole circuit.
The travelers
The two remaining screws are travelers, and they only ever talk to the travelers on the other switch. The lever picks which traveler the common is bridged to. Two switches each picking one of two paths gives four combinations, and the light is on in exactly two of them.
It does not matter which traveler
Cross the two travelers and the circuit still works — it just inverts which lever position means on. That is why this game simulates the circuit instead of grading against one diagram. Both wirings are correct.
The neutral never switches
The grounded conductor runs unbroken from the panel to the fixture. Switch the neutral instead of the hot and the lamp still works perfectly — while the socket stays energized with the switch off. It is the most dangerous way to be right.
The real thing
We do this for a living
Motor control centers, VFDs, PLCs, and plant controls across Northern Colorado. Considerably more terminals, same principles.