Occupancy sensor wiring diagram

Light: on

Move the space between occupied and vacant. A real sensor adds a time delay so a still person does not get left in the dark — the switching itself is this simple. The copper highlight is the live path, not a wire colour.

An occupancy sensor is a switch the room operates: it closes when it detects a person and opens again after the space has been empty for a set time. Wired in the hot to a fixture, it turns the light on when you walk in and off a while after you leave. Move the diagram between occupied and vacant to see it work.

How this circuit works

Like the photocell, this is a single switch in the hot line — the shape of a plain single-pole. The difference is the trigger. Presence closes the contact and the hot reaches the lamp. Absence, once the hold-off timer expires, opens it again. The timer is the only thing between it and an ordinary switch, and it matters more than it looks: without it the light would flick off the moment you held still.

Whether it turns on by itself (occupancy) or only off by itself (vacancy) is a setting on the same device, not a different circuit. Both leave the switching topology exactly as shown here.

Questions people ask

How does an occupancy sensor switch the light?

It detects a person — usually by their movement or body heat — and closes a switching contact to bring the light on. When it stops detecting anyone, a timer runs down and then it opens the contact and the light goes off. Electrically it is just a switch that the room operates.

What is the difference between occupancy and vacancy sensing?

An occupancy sensor turns the light on automatically when someone arrives and off when they leave. A vacancy sensor only does the off half — you switch it on by hand, and it turns off for you once the space empties. Same detector, different rule about the on part.

Why does the light stay on when I sit still?

The hold-off timer. A motion-based sensor can lose you if you stop moving, so it waits a set time after the last detection before switching off. That delay is why a still person is not suddenly left in the dark — and why the light lingers a while after you leave.

Photocell wiring — switched by daylight instead of movement.
Single-pole switch wiring — the same circuit with a hand switch.
All wiring diagrams

Learn one thing a week

Now and then a new diagram, drill, or reference sheet goes up. Leave your email for a short heads-up when it does — no spam, no selling it on, one click to leave.