Shitty LED Lights Mod

Before Christmas, I needed a battery case for a last-minute present. Much to my surprise, I had nothing fitting in my big box of parts. So, I went to the overpriced decorative crap store and bought one of those ultra-cheap led lights. Except this one wasn’t cheap. Likely 2x the online price, and at least 10x the manufacturing cost. But hey, it came with batteries included.

Back at home, I cut the battery compartment box, finished my present (it didn’t work, for reasons totally unrelated to this), and threw the lights aside.

Then, some days after Christmas, I stumbled across this reddit post of someone who turned fairly similar lights into USB-powered ones. “Huh, nice”, I thought.

Then, today, I found myself absolutely fed up with writing the paper I am supposed to write. Too tired to play games and too wired up to relax with some book, I decided to replicate that little project.

The starting point was easy, I found a piece of scrap circuit board with a mini USB connector conveniently soldered on. I cut off some used parts, unsoldered a bit of old stuff, and there we go!

Next step: Voltage. Originally, this thing ran on three 1.5V AA batteries, with one (1) current-limiting resistor. However, it had a little sign telling me that it was supposed to run on 3V, 20mA.

So, being the overengineering idiot that I am, I decided to give it just that. The first attempt used a LM317 variable-voltage linear converter. However, no light. Hm.

I double-checked everything, and I decided that my LM317 was just dead. I’m writing this during the (extended) chip crisis of 2022, so I’ve lost roughly half my life savings there.

Attempt number two: I found a 7533. If you don’t know this, the 75XX is a series of old and trusty devices that regulate the output to whatever “XX” is (in my case, 33, meaning 3.3V). This time, everything went well. I even went the extra mile and gave it some current limiting and strain relief.

And, the whole thing:

As you can see, I was not happy with the amount of light and the current limiting, and kept piling on resistors to make it brighter. It took me more time than I am willing to admit to decide that my whole voltage converter idea was stupid. LEDs are current-driven after all, the overall current here is negligible, and I probably spent more time on them than the overworked engineer designing them and the poor sweatshop worker assembling them. Combined.

So, I got rid of the 7533, and replaced it by a strategic solder bridge. The only downside is that the circuit board looks sad and empty now. Meh, can’t have everything.

Note to self: When at my parents’ house, nick a spare USB charger.