#FET TRANSISTOR FOR MULTIPLE LEDS DRIVERS#

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.

#FET TRANSISTOR FOR MULTIPLE LEDS DRIVERS#

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. 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.

Fet transistor for multiple leds