Build an RGB LED Controller

Using Parallel FET Dimming There are a lot of fun and interesting things you can do with LEDs and the different ways to control them. In this article, Dirceu describes an alternative approach to control RGB LEDs, using the parallel FET dimming technique. He steps through his efforts to design and build an alternative lighting system based on power RGB LEDs. To control them he goes very old school and uses an 8-bit MCU and the BASIC programming language. Nowadays, applications involving advanced processors like Arm and Espressif ESP-32 are commonplace. But I thought it would be cool to test some fun lighting sequences that are controlled by an 8-bit microcontroller (MCU) programmed using an ancient language: BASIC. Although using pulse-width modulation (PWM) to dim LEDs with MCUs is a long-established idea and there’s a plethora of such products on the market, my approach differs from others regarding the drive method used. The benefit will be a relatively shorter BOM, but is also of particular interest to embedded system designers involved with LEDs because it will be possible to experiment with alternative configurations for the control stage. LEDs are inherently nonlinear devices. Their brightness depends primarily on the current flowing through them, even though the voltage on terminals don’t vary that much. To achieve a constant LED current, there are two approaches: linear or switched current regulation. A linear regulator is preferred in situations where the noise due to commutation would be unacceptable—or for example, in high-precision measurement equipment. When efficiency is the main concern, a switched regulator or driver usually is chosen. A commercially available driver usually operates above 1 MHz, providing hysteretic regulation for the LED current. To implement the required dimming, a common solution is to apply a PWM signal to an enable pin of the regulator. Because the entire component is switched continuously, the delay due to th