Learn How to Build Microcontroller and IC-Free NeoPixels!

Adafruit NeoPixels, along with generic individually-addressable RGB LEDs, have exploded in popularity in recent years, because they’re easy to use, affordable, and very versatile. Unlike traditional RGB LEDs that are simply three or four LEDs joined by a common cathode or anode, NeoPixels (WS2812B or SK6812 LEDs) contain tiny little driver IC (Integrated Circuit) chips built into the package that provide control over the individual LED colors. That makes it easy to chain them together in strips and pass a signal from one to the next using a microcontroller. But it is possible to do something similar using standard LEDs and no ICs at all. That is what Gammawave has demonstrated with their fantastic Discrete Chain Link Oscillator Instructables project.

While this LED strip doesn’t have nearly the level of flexibility as a strip of NeoPixels, it does have a number of similarities. Namely, you can chain multiple LED modules together and they will act as a group cooperatively. But you cannot change the behavior of the LEDs without swapping out components or redesigning the circuit. The LEDs will only do one thing: flash on and off in sequence, one after the other. This is very similar to the LED “chaser” circuit that we featured last month, which was also built using only discrete components. This is based on an astable multivibrator oscillator circuit, but with the two “halves” of the circuit broken out into individual blocks. Those blocks can be chained together to form the LED strip.

A standard astable multivibrator circuit oscillates between two states using transistors that are triggered by the charging and discharging of capacitors, with one half of the circuit flipping the state of the other half and vice-versa. Normally, that would blink one or two LEDs consistently, with the timing dependent on the values of the capacitors and resistors used in the circuit. In this case, one circuit block in the chain controls the state of the subsequent block in the chain. It’s like the LED chaser circuit, but with as many LEDs blocks as you like. This isn’t quite as seamless as a chain of NeoPixels, as the final block in the chain has to roll back over and control the state of the first block in the chain. Given the realities of manufacturing and mass production, these are also probably going to be more expensive than WS2812B LEDs that offer a lot more functionality. But this project does a fantastic job of illustrating how good ol’ discrete components can be used to achieve some surprisingly complex results if you’re clever.