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Potentiometer
• Variable Resistor with 3 terminals
• Side Terminals: 1 and 3
• Middle Terminal: 2
• Rotate the knob and resistance changes
• Smaller version of Rheostat
Potentiometer
Variable & Fixed Resistance• A resistor has only two ends
• Variable Resistance: Use terminal 2 and any side terminal (1 or 3)
• Fixed Resistance: Use side terminals (1 and 3)
• Rotate the knob and resistance changes
• Examples: Fan Regulator, Volume Control
Schematic Symbol
Inside Potentiometer
Inside Potentiometer
• Resistance between 1 and 3 = Resistance between 1 and 2 + Resistance between 2 and 3
• R13 = R12 + R23
• R13 = Fixed Value = Imprinted on the component
• Rotate towards terminal 1: R12 decreases and R23 increases; total sum of R12 and R23 remains constant
• Rotate towards terminal 3: R12 increases and R23 decreases; total sum of R12 and R23 remains constant
Preset• Same as potentiometer
• More Portable
• Slot on the preset
• Insert screw driver inside slot to change resistance
• Variable Resistance: (1,2) or (2,3)
• Fixed Resistance: (1,3)
Schematic Symbol
Recommendation: In booklet, we have used symbol of a potentiometer to denote a preset. You can safely use a preset in place of potentiometer.
Preset as Voltage Divider
• Provide Vcc to terminal 1
• Provide ground to terminal 3
• Take output from terminal 2
• Output at terminal 2: Variable Voltage
• Rotate preset and measure voltage at pin 2
Preset as Voltage Divider
Preset as Voltage Divider
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