photocell circuit diagram
This is a free printable photocell circuit diagram: download the diagram as SVG or open it and print to paper or PDF.
The photocell circuit diagram circuit demonstrates advanced power distribution and automation control principles. This system integrates multiple load branches with coordinated protection, enabling sophisticated industrial and commercial applications. The circuit implements hierarchical protection: a main breaker provides primary protection, individual fuses protect each load branch, and contactors enable remote automation. Component spacing exceeds 100 pixels ensuring PCB manufacturability and technician accessibility. The Manhattan routing protocol maintains horizontal and vertical wire segments exclusively, eliminating diagonal routing. Each branch operates independently while sharing common ground reference, enabling parallel load expansion.
How to wire photocell circuit diagram
- Select the correct photocell for the application Match the photocell switch rating to the total wattage of the connected lights. A 1 000 W photocell handles most domestic LED and halogen security lights. For commercial street lighting above 1 kW, use a photocell to trigger a contactor rather than switching the load directly.
- Identify the three photocell wires Standard photocell wire colours are: black or brown (line input), blue (neutral), and red or black/white (switched load output). If the colours differ from your photocell, check the manufacturer's label on the body of the unit before connecting.
- Connect line input to supply live Connect the photocell line input wire to the incoming live from the distribution board MCB. Use a terminal block inside the junction box to make all joins. Do not rely on taped connections for outdoor wiring — use weatherproof junction boxes rated IP65 minimum.
- Connect neutral wire Connect the photocell neutral wire to the neutral link in the junction box. The neutral wire does not switch — it connects directly and permanently to the neutral supply.
- Connect load output to the light fitting Connect the photocell load output wire to the live input terminal of the light fitting. The light fitting neutral connects directly to the neutral link. The photocell interrupts only the live path to the fitting.
- Position the sensor correctly Mount the photocell facing north (in the southern hemisphere) or in open sky away from artificial light sources, walls, and overhangs. A photocell reading reflected light from a nearby wall will not detect dawn accurately and may fail to switch off in the morning.
- Test dusk and dawn operation Cover the photocell sensor completely — the light must come on within 10 seconds. Uncover the sensor — the light must go off. Adjust the sensitivity pot on the photocell body if available to set the exact light level threshold for switching.
Frequently asked questions
What is a photocell and how is it wired?
A photocell (also called a photoelectric switch or dusk-to-dawn sensor) is a device that switches a load on at low light levels and off in daylight. It is typically wired in series with the live feed to a lighting circuit. The photocell has three wires: line in, load out, and neutral.
How do I wire a photocell to a street light or security light?
Connect the photocell live input wire to the switched live from the distribution board. Connect the neutral wire to neutral. Connect the load output wire to the live input of the light fitting. The light fitting's own neutral connects directly to the neutral rail. The photocell switches the live feed only.
Why does my photocell light stay on all day?
The most common causes are the photocell facing a dark wall or being shaded, the sensitivity set too high, or a failed photocell stuck in the closed (on) position. Reposition the sensor to face open sky. If repositioning does not fix it, test by disconnecting the load wire — if the light goes off, the photocell is failed.
Can a photocell control a three-phase external lighting circuit?
A standard single-phase photocell controls one phase and neutral only. For three-phase lighting, use a photocell to trigger a contactor coil rather than switching the load directly. The contactor then switches all three phases. Never run three-phase current through a single-phase photocell contact.
What is the maximum load a standard photocell can switch?
Standard domestic photocells typically switch up to 1 000 W at 230 V AC. LED loads are usually well within this limit, but high-power metal halide or sodium street lights may require a contactor rated for the load, triggered by the photocell output rather than switched directly.
Related diagrams
- 1 to 4 demultiplexer circuit diagram
- 12v bms circuit diagram
- 12v dc power supply circuit diagram
- 12v inverter circuit diagram
- 12v regulated power supply circuit diagram
- 12v relay module circuit diagram