What Is 3 Pin, 5 Pin & 7 Pin NEMA Photocell Receptacle?

At the top of many street lights and parking lot lights, you may notice a small blue or black knob. Surprisingly, this knob is actually a lighting control device. The most commonly used control is a dusk-to-dawn or photocell device. The receptacle can be used for dusk-to-dawn sensors, as well as for advanced DALI/Bluetooth controls.

The NEMA standard sets the 3, 5, and 7 pin system for photocell receptacle, which is widely used in the lighting industry. These receptacles all have the same 3-pin twist lock system, making them easily interchangeable. While the 5 pin and 7 pin options offer added features, such as greater control over lighting intensity, all three options can be used to enhance energy efficiency and reduce lighting costs. But what are these different pins for, and how do they work?

1.  3 Pin Receptacle

A 3pin NEMA photocell receptacle is the simplest and most common type of receptacle. It consists of three pins that are used to control the on/off switch for the lighting fixture. In the picture, you can observe the slots designated for the photocell prongs, which establish the necessary connections. One pin is used for the power source, while the other two pins are used to control the closing and opening of the circuit. These connections link your hot input power to the photocell and the output from the photocell to your light fixture, alongside the neutral wire, requiring three connections in total.

When it grows dark, the photocell permits the input power to pass directly to your fixture through the output side of the receptacle, thereby illuminating your light. This type of photocell is typically used in smaller outdoor lighting systems that do not require advanced features.

2. 5 Pin Receptacle

A 5pin NEMA photocell receptacle is designed for more complex lighting systems. It is very similar to the 3 Pin receptacle, with the only difference being that it has two additional contacts on its surface. These contacts are accompanied by two wires on the backside of the receptacle, which are usually connected to 0-10V dimming leads on an LED driver. Additionally, these contacts may also be utilized for other sensors inside a fixture housing where the receptacle is installed. This allows the user to adjust the brightness of the light to their desired level.

5pin systems are commonly used in larger outdoor lighting systems, such as sports stadiums and parking lots.

3. 7 Pin Receptacle

A 7pin NEMA photocell receptacle is the most advanced type available. Just like a 5 Pin receptacle, a 7-pin receptacle retains the standard 3-pin sockets, but features an additional 4 contacts on its surface and 4 corresponding wires on the reverse side. These pins are used for advanced control options, such as motion detection and overall lighting control.

7pin systems are commonly used in high-security areas, such as prisons and military bases.

In all three types of NEMA photocell receptacles, the photocell itself is located within the lighting fixture. The photocell responds to changes in light conditions, and switches the lighting fixture on and off as required.

In conclusion, NEMA photocell receptacles are an important part of outdoor lighting systems. They provide an easy and energy-efficient way to control lighting, while also providing safety and security. The different types of NEMA receptacles offer a range of features to suit different needs, from simple switches to advanced lighting control systems.