If you switch between the LEDs really fast, the persistence of vision will make them look like they’re all on. As the LEDs turn on only when they have voltage on the anode and ground on the cathode and do nothing in any other situation, it is possible to connect a lot of LEDs to a small number of microcontroller pins in all the physically possible ways and turn them on one by one, turning one pin high, one low, and keeping the rest in input mode. These pins can be active high, active low and passive (aka input, or high impedance state). These techniques are often mixed up, but, while their basic principle (persistence of vision) and their end result are relatively the same, the ways they achieve this result are fundamentally different, and it is important to understand the difference right from the start to avoid confusion later.Ĭharlieplexing relies on the tri-state nature of the microcontroller pins. There are two main techniques employed when multiplexing LEDs. There is a certain wow-factor, however, so some fun will be provided. With these two projects, I’m trying to help better understand the ways multiplexing, timers and interrupts work. There are better ways to control multiple RGB LEDs off an Arduino. Please note that this Instructable is educational, not practical. 1 demux chip, either 74HC138 or 74HC238 3 or 8 MOSFETs, P-Channel or N-Channel respectfully 6 or 16 RGB LEDs, either common anode or common cathode So, to test the stuff explained here, you’ll need: It’s very easy to switch between the N- and P-Channel MOSFETs, provided you also use a different type of LEDs and demux chip I’ll give the details. But, alas, I have only three P-Channels MOSFETs in breadboard-friendly packages. In most cases, you should stick to the first pair while dealing with LEDs, as all the LED drivers are current-sinking devices. The first project will be common-anode LEDs and P-Channel MOSFETs, the second one will use common cathode LEDs and N-Channels. The first one drives 6 RGB LEDs using just three MOSFETs the second one drives 16 LEDs but needs eight MOSFETs and a demultiplexing chip. And to do this, I built a couple of devices that use the bare minimum of hardware between the Arduino and the RGB LEDs to make the clearest possible picture of how the multiplexing works. There are a lot of Instructables dealing with multiplexing, but most of them describe the particular project and do not cover the basics I decided to amend that. ReadChar = Serial.There are multiple ways to light a lot of LEDs off an Arduino (or any other microcontroller): shift registers, LED drivers, programmable LEDs, but the more LEDs you want to control, the closer you’re getting to the multiplexing: the ultimate technique for driving hundreds and thousands of LEDs. Open your Arduino IDE and go to File > New to open a new file. HC-05 Bluetooth Module Interfacing with Arduino with LED Control Example.Picture of both common anode and common cathode types RGB LED is shown below: Common Cathode type: In common Cathode type, Cathode of all three light emitting diodes are common and common cathode terminal is connected with ground of power supply and other terminal of each power LED is connected with pic microcontroller according to which LED we want to turn on or turn off.Other terminals connects with microcontroller and we turn on and off these terminals according to which LED we want to turn on or turn off. Common Anode type: In common Anode type, Anode is common for all three Light emitting diodes and Anode of all the light emitting diodes connects with positive power supply.There is two types of RGB light-emitting diodes are available in the market. The longest pin is either the anode or the cathode depending on the type of the RGB LED. These pins are used in order to control the color of the LED. Whenever voltage is applied to the red terminal, a red light will emit, and similarly when the voltage is applied to the Green and blue terminal, green and blue lights will emit respectively. RGB LED is a light-emitting diode that emits red, green, and blue lights. It consists of three discreet LEDs: red, green, and blue housed in a single packet so by combining these three colors we can create any color. Android Smartphone with MIT AI2 Companion installed.
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