Voltlog #197 – Wiring LEDs Correctly Series vs Parallel

Welcome to a new Voltlog, today we’re talking about LEDs, light emitting diodes and how we can connect them if we have multiple units. This is one lesson I wish I knew from the start because back when I started tinkering with electronic circuits I built a few projects with LEDs which let’s say could have been made better if I knew the stuff I’m gonna present in this video.

So let’s start by giving you a short story about this project I built back in 2010 so, 10 years ago I saw this project made by Ladyada, I believe back then Adafruit was just starting, they were selling just a few kits. The project was called tv-b-gone and it was a small microcontroller with an IR emitting diode, and it contained power off codes for most available tvs. The purpose was to point it at a TV, upon activation it will cycle all the codes and eventually the TV would turn off. Obviously a fun project that could potentially torment those around us.

So I decided to use a bunch of IR LEDs to increase the power of this circuit. And this is where I made the mistake of having all LEDs in parallel each with its own current limiting resistor. This meant I had to drill and install a bunch of different resistors and due to variations in the resistor value, the leds were running at slightly different currents, outputting slightly different power levels.

If I were to redo the circuit today I would probably connect them in series and use a boost circuit to drive the series string with constant current.

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