Slide-Potentiometer

This chapter will show you how to connect a potentiometer to your Arduino board read the current value of the potentiometer from JavaScript.

What is a slide potentiometer?

A slider potentiometer works the same way a knob potentiometer does, but instead of changing the resistance by turning a knob, you change it by sliding.

There are different types of slide potentiometers:

  • Linear slide potentiometers changes the resistance evenly (linear). Sliding 25% will increase / reduce the resistane by 25%.

  • Logarithmic slide potentiometers will change the resistance in a curve. This means, that you might have slided 50%, but the resistance is already up to 75%.

While logarithmic sliders are usually recommended when builing audio-faders, I would recommend buying a linear slide potentiometer for your project. If you accidently got a logarithmic one, you can compensate this with a little math.

If you are sure you bought a linear poti, but the damn thing keeps bevahing like a logarithmic one, double check your wiring! Usally you accidently switched the +5V with the A0 connection.

Connecting the potentiometer with p5js

The basic syntax is:

let poti = connectSensor( SENSOR_POTENTIOMETER, pin, minValue, maxValue );

In the follwing example we will setup a potentionmeter which was connected to the A0 (Analog 0) pin. If you don’t define a minValue and maxValue, the values returned by calling poti.vale() will range from 0 to 1024:

let poti = connectSensor( SENSOR_POTENTIOMETER, 'A0' );

Here we would like the potentiometer to be mapped to values 0 and 100:

let poti = connectSensor( SENSOR_POTENTIOMETER, 'A0', 0, 100 );

Hardware

Wiring

There are many types of slide potentiometers. Some come with 3 pins, some with 5 or 6 pins. Sliders with more than 3 pins usually have 2 separate / parallel wiring options (OTA and OTB).

What you will need to find out, is which of the pins needs to be connected to GND, +5V and your analog pin (i.e. A0). Usually you will find a wiring scheme in the internet or on the manufacturer’s website.

You will find several synonyms for the pins:

Pin on slide poti

Synonyms

Connects to Arduino

OUT

OTA / OTB, SIG, S, OUT

Analog IN, i.e. pin A0

VCC

VCA / VCB, V, +

+5V

GND

G, -

GND
Wiring Arduino p5js Javascript

Code

let poti;

function setup () {
   createCanvas(400, 400);
   poti = connectSensor( SENSOR_POTENTIOMETER, 'A0', 0, width );
}

function draw () {
   background( 255 );
   circle( 200, 200, poti.value() );
}