Potentiometer

Rotary or linear-travel potentiometer controlled by physical signal

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  • Simscape / Electrical / Passive

  • Potentiometer block

Description

The Potentiometer block represents a rotary or linear-travel potentiometer, with the wiper position controlled by the input physical signal.

If the potentiometer resistance changes linearly based on wiper position, then the resistance between the wiper position and port L is:

RWL=R0xmax−xmin(x−xmin)

where

  • RWL is the resistance between the wiper position and port L.

  • R0 is the total resistance between ports L and R.

  • x is the wiper position.

  • xmin is the value of the wiper position when the wiper is at port L.

  • xmax is the value of the wiper position when the wiper is at port R.

If you specify Logarithmic for the potentiometer resistance Taper parameter, then the resistance between the wiper position and port L is:

RWL={A(eλ(x−xmin)−1)if resistance gradient is higher at RR0−A(eλ(xmax−x)−1)if resistance gradient is higher at L 

where A and λ are chosen such that RWL at xmax is R0, and RWL at x = (xmax + xmin) / 2 is equal to Rav, the resistance when the wiper is centered.

Note

Potentiometers widely described as LOG or logarithmic taper are, in fact, exponential taper. That is, the gradient of the resistance between wiper and left-hand port increases as the resistance increases. The Potentiometer block implements this behavior.

For both linear and logarithmic tapers, the resistance between the wiper position and port R is:

RWR=R0−RWL

where

  • RWR is the resistance between the wiper position and port R.

  • R0 is the total resistance between ports L and R.

  • RWL is the resistance between the wiper position and port L.

Ports

Input

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Physical signal input port controlling the wiper position.

Conserving

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Electrical conserving port associated with the potentiometer left pin.

Electrical conserving port associated with the potentiometer right pin.

Electrical conserving port associated with the potentiometer wiper pin.

Parameters

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The resistance between port L and port R when port W is open-circuit.

The lower limit placed on the resistance between the wiper and the two end ports. It must be greater than zero. A typical value is 5e-3 times the total resistance.

If you select Higher at R for the Resistance gradient parameter, then Resistance when centered is the resistance between port L and port W when the wiper is centered. Otherwise, if you select Higher at R for the Resistance gradient parameter, then Resistance when centered is the resistance between port R and port W when the wiper is centered. Because the resistance taper is exponential in shape, the value of the Resistance when centered parameter must be less than half of the Total resistance parameter value.

Dependencies

This parameter is visible only when you select Logarithmic for the Taper parameter.

The value of the input physical signal at port x that corresponds to the wiper being located at port L. The default value is 0.

The value of the input physical signal at port x that corresponds to the wiper being located at port R. The default value is 1.

Specifies the potentiometer resistance taper behavior: Linear or Logarithmic.

Specifies whether the potentiometer resistance varies more rapidly at the left or the right end: Higher at L or Higher at R.

Dependencies

This parameter is visible only when you select Logarithmic for the Taper parameter.

Model Examples

PWM Circuit Using 555 Timer

PWM Circuit Using 555 Timer

A pulse-width-modulated (PWM) output implemented using a 555 Timer in astable mode. The duty cycle is set by a potentiometer, P1. The potentiometer is controlled during run-time via Duty Cycle Control Knob. The scope shows the resultant output from the 555 Timer. To end the simulation, click on the Stop button.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

See Also

Introduced in R2010a

Simscape Electrical Documentation

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