A 12-volt circuit typically pertains to 12-volt direct current (DC) electricity commonly used in electronic appliances and other low-voltage applications. Almost all types of 12-volt DC circuits have a switch or control device that allows a user to turn the power on or off. A 12-volt switch can come in various styles and shapes and can have different features, but almost all kinds of 12-volt switches follow the same basic wiring procedure. A positive wire runs from the power supply to the input terminal of the switch, and another wire runs from the output terminal of the switch to the 12-volt appliance.
The 12-volt Switch
Twelve-volt switches have many applications and come in many forms, but the on/off switch, which can be a toggle, rocker, or push/pull switch, and the momentary switch, which can be a push button, starter, or timer switch, are the most common types of 12-volt switches. Twelve-volt switches are basically classified as single pole, single throw (SPST) switches, or single pole double throw switch (SPDT). SPST 12-volt switches have one terminal that connects to the power supply and another terminal that connects to the load. SPDT 12-volt switches have a third terminal that allows the user to connect a second load to the power source.
The Power Supply
The most commonly used power supply of a 12-volt switch is a 12-volt battery, but an electrical transformer that converts 110 or 220 volts of AC electricity into 12 volts DC electricity is also used by appliance manufacturers. No matter which power source is used, a 12-volt switch must only be used with an original or converted 12-volt power supply. A 12-volt DC power supply always has a positive and a negative terminal and it is always the positive terminal that is wired to the 12-volt switch.
Most 12-volt circuits use 18 and 16 gauge AWG standard wires for loads rated up to 15 and 30 amperes, but you must know the amperage of the load you are wiring, and you must check an AWG wiring chart to know the right size of wire to be used. The positive wire running from the battery must be wired to one terminal of an SPST switch, or to the middle terminal of an SPDT switch. The load must be wired to the other terminal of the SPST switch, or to the two terminals of an SPDT switch.
A 12-volt circuit is made of a 12-volt power supply wired to a 12-volt appliance.The 12-volt direct current electricity has a positive and negative polarity and is carried by electrical wires from the power source to the appliance. The negative terminal of the power supply is connected to the negative side of the load while the positive terminal is connected to the positive side of the load. A 12-volt switch controls the operation of the appliance by discontinuing the flow of electricity through the positive wire. A fuse discontinues the flow of electricity in case of a short circuit.
A fuse is an electrical safety device that cuts the flow of electricity whenever there is a short circuit. A 12-volt circuit must be protected by a fuse to prevent fire and damage to the appliance. The fuse must be placed between the switch and the power source. A fuse has two terminals, and one terminal must be connected to the wire coming from the power source. The other terminal must be connected to the wires running to the switch. A fuse must be rated according to the amperage of the appliance or load.