How to Wire a Battery Operated Switch

Batteries are used to power electrical circuits of all sorts. However, these electrical circuits would soon drain the battery if there were no way to turn the circuit off. Therefore, using an electrical switch to turn a circuit on and off is important to conserving energy. One type of switch, an electrical relay, is operated by applying electrical energy (such as power from a battery) to the relay leads. This relay will then switch a second electrical circuit on. These switches allow for a low-voltage power source to switch a high-power circuit on and off safely. However, a relay must be wired correctly; otherwise neither circuit will work properly.

Things You'll Need

• One 12-volt battery
• One 24-volt battery
• Electrical wire
• Electrical pliers
• Soldering iron and solder
• Four battery terminal connectors
• One "single pole, double throw" (SPDT) relay switch
• One "single pole, single throw" (SPST) switch
• One light bulb
• One light bulb receptacle

Instructions

1. Cut a length of wire and strip each end of 1/2 inch of insulation. Attach one of the battery terminals to one end of this wire, and solder the connection. Attach the other end of this wire to the first relay coil connection (terminal 85), and solder the electrical connection. Cut a second length of wire and strip each end of 1/2 inch of insulation. Attach one end of this wire to the second relay coil connection (terminal 86), and solder this connection. Attach the other end of the second wire to one of the terminals on the SPST switch. Connect the battery terminal to the positive battery post on the 12-volt battery.

2. Cut a third length of wire, and strip each end of 1/2 inch of insulation. Attach one of the battery terminals to one end of this wire, and solder this electrical connection. Attach the other end of this wire to the second terminal on the SPST switch, and solder the electrical connection. Ensure that the switch is in the "Off" position. Connect this battery terminal to the negative battery post on the 12-volt battery.

3. Cut a fourth length of wire, and strip each end of 1/2 inch of insulation. Attach one end of this wire to the relay Common terminal (terminal 30), and solder this connection. Attach the other end of this wire to a battery terminal connector, and solder the connector to the wire. Connect this battery terminal to the positive battery post on the 24-volt battery.

4. Cut a fifth length of wire, and strip each end of 1/2 inch of insulation. Connect one end of this wire to the normally open terminal (terminal 87) on the relay, and solder this connection. Connect the other end of this wire to one of the light receptacle terminals. Cut a sixth length of wire, and strip each end of 1/2 inch of insulation. Attach one end of the sixth wire to the unoccupied light receptacle terminal. Attach the other end of this wire to a battery terminal connector, and solder this connection. Connect this battery terminal connector to the negative battery post on the 24-volt battery.

5. Install the light bulb in the light bulb receptacle. Turn the SPST switch on. The relay will click, and the light will illuminate.

References

• AutoAnything.com: How A Relay Works
• 12-volt: Single Pole Double Throw Relays