It consists of an Arduino-compatible Shield with a PhotoCell Sensor, one 12v Relay, and a two-position Dip Switch. This PhotoCell Relay Kit will plug directly on top of your Arduino UNO.

The PhotoCell is connected so that an incoming light, such as a Laser Pointer, or other light source, will cause the Arduino Input Logic level to go from a Logic 1 to a Logic 0. This is read by your Arduino Project Code and will do whatever you wrote to do. Now you can control items with a Laser Pointer!

The Relay is controlled by the Arduino Digital outputs and the DIP Switches are connected to the Digital Inputs. The PhotoCell Sensor is connected directly to the Analog Inputs. There is a 2-pin screw terminal for an external 12vdc to power the relays. This 12vdc is also connected to the Arduino VIN input so that both units can be powered by the 12vdc coming in. This means you can write your program, load it into the Arduino, and then relocate both units to anywhere that you need. They do not need to be connected to the computer once it is programmed. The required external 12vdc power supply is not included.

The Relay is an 833H series SPDT relay with Form 1C contacts rated for 7 Amps @ 250VAC. It has a 12VDC coil. Each set of Relay contacts are available at a dedicated 3-pin screw terminal. The available contacts are the Common (COM), NO (Normally Open) and NC (Normally Closed). This means that the circuit can either turn devices ON for a set time period or turn those devices OFF for a set time period.

You can now control many different 120 VAC devices, such as your Christmas lights, sprinkler system, garage door, etc with the program you write using your Arduino UNO. Have them alternate back and forth for a nice effect.

This kit is now offered with a "Built & Tested" option for those that do not want to build it themselves.

This is one of the first practical applications for Arduino that you will find. There are several combinations available, such as the number of PhotoCells and the number of Relays. The default value is one PhotoCell and one Relay.

You will get a schematic and all of the parts to assemble a working unit. This kit does not include the tools you will need to assemble the circuit. You will need tools such as a soldering iron, solder, wire cutters, etc. Below is a detailed introduction to component identification and kit assembly.