Video
Circuit Diagram
Source Code
1// ─────────────────────────────────────────
2// BlueGrays · bluegrays.com
3// LED Chaser with Adjustable Speed
4// ─────────────────────────────────────────
5// A potentiometer sets the speed of the walking LED effect. A0 is read at
6// every step and its 0-1023 value becomes the delay time (ms).
7//
8// Pins:
9// D2, D3, D4, D5, D6, D7 -> 6 LEDs (in order)
10// Each LED with a 330 ohm resistor
11// A0 -> Potentiometer wiper
12// (outer legs to 5V and GND)
13
14int ledPins[] = {2, 3, 4, 5, 6, 7}; // LED pins in lighting order
15int potValue; // Pot value = delay (ms)
16
17void setup() {
18 // Set all LED pins as outputs
19 for(int i = 0; i < 6; i++) {
20 pinMode(ledPins[i], OUTPUT);
21 }
22}
23
24void loop() {
25 for(int i = 0; i < 6; i++) {
26 potValue = analogRead(A0); // Read the speed (0-1023)
27 digitalWrite(ledPins[i], HIGH);
28 delay(potValue); // Wait as many ms as the pot value
29 digitalWrite(ledPins[i], LOW);
30 }
31}
32FAQ
What values does `analogRead` return?▾
The Uno's analog inputs read 0–5 V with 10-bit resolution and return a value between 0 and 1023. As the potentiometer is turned from one end to the other, the value changes from 0 to 1023.
How do we convert the potentiometer reading to speed?▾
Using the `map()` function, you can convert the 0–1023 range to any delay range you want (e.g., 20–500 ms): `map(value, 0, 1023, 20, 500)`. When this value is used inside `delay()`, the speed changes instantly.
How do you connect the leads of a potentiometer?▾
The two outer pins are connected to 5 V and GND, and the middle pin (wiper) is connected to an analog input (e.g., A0). If you connect the outer pins in reverse, only the rotation direction will reverse; the circuit will not be damaged.
Changes in speed are detected with a delay—why?▾
If the potentiometer is read only at the beginning of the loop, the new value is not applied until all the LEDs have lit up. If you include the reading within each LED step, the speed changes instantly.