overview and Video
The objective of this project is to learn how to create an LED bar graph.
The bar graph is a series of LEDs in a line, similar to what you might see in an audio display. It is controlled by an analog input (the potentiometer), but it could be anything else that puts out a varying analog signal, such as a microphone.
When this project is successfully built, you can rotate the potentiometer knob, and the LEDs will light up or go dark one at a time, in sequence.
This is project 3 from the Arduino Project Handbook, V1 by Mark Geddes.
We built this project on a WorkBench Project Development Kit from Phase Dock.
you will need
One 400 pin breadboard
“Always-on” battery (optional; this project can be powered from your computer)
Nine LED lights (red, yellow, green)
Nine resistors (330 - 500 ohm work best)
Potentiometer (50k or above)
WorkBench 1007 with two 2x3 Clicks, one Arduino Slide
Optional: one 2x3 or 1x3 Click depending on the size of your battery
Optional: 1007 Cover
Arduino Project Handbook, Volume 1, by Mark Geddes; this is Project 3
You can purchase the book (we recommend supporting Mark’s work).
You can download the sketches and libraries (code) for these projects.
Links are provided for your convenience; as an Amazon Associate Phase Dock Inc. earns from qualifying purchases. These products may be available from other sources.
1. We found using a 330-ohm resistor worked better than a 220 ohm. The 220 ohm is exceptionally bright. A 500 ohm resistor should work fine as well.
2. LEDs can short out if you are not careful about how you handle and install them. A lack of resistors can cause them to short out. We also suggest leaving your potentiometer in the closed position (fully counter clockwise) until ready to use.
3. Depending on the quality LED’s you have, some may fail to work right out of the box. If one LED doesn’t light but the rest do, try replacing the LED with another before you troubleshoot the circuit. Be aware If the LED doesn’t light…you may have it in backwards. (LEDs are directional and they only work one way.)
4. Leave at least one space on the breadboard between the LEDs. You will find it easier to insert the resistors and the control wires if the LEDs are not packed together too tightly.