A variable resistor allows for a portion of a circuit to have its resistance altered by the turn of a knob, useful for applications such as dimmer switches and temperature controls on heaters. Originally known as a rheostat, the variable resistor was an individual component but has since been mostly replaced by the potentiometer. A potentiometer ("pot") can be wired for several other uses, such as a volume control, but can easily be configured to work as a variable resistor. When selecting a pot to use as a variable resistor, remember that its rating indicates its maximum resistance. Also, linear taper pots have a more precise response compared to logarithmic pots and are better suited for variable resistor applications.
- Skill level:
- Moderately Easy
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Things you need
- Insulated copper wire
- Wire cutter
- Wire stripper
- Soldering iron
- Rosin core solder
Identify the terminals on the potentiometer. With the post upright and the terminals facing towards you, they are referred to as "1," "2" and "3" from left to right.
Solder a wire to terminal "3" inline with the portion of the circuit you want the variable resistor to act upon.
Cut a short piece of wire and strip about one-quarter-inch off each end.
Jump terminals "2" and "1" by soldering the wire between the two.
Solder a wire from terminal "1" back to the circuit to complete the signal path.
Use the knob of the potentiometer to vary resistance. At "0" the resistance will be negligible and at "10" the pot will operate at its full rated resistance.
Tips and warnings
- Work carefully with your soldering iron. Its high heat can cause serious burns and the process of soldering produces fumes that are harmful if inhaled.
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