I have this string of USB powered LED fairy lights that came with an IR remote. I had initially planned to plug these into a smart outlet, using a phone charger adapter, in a place that isn't easily reachable by the remote and use the outlet to turn the lights on and off.

The LEDs have 8 modes to them and I only want them to stay on constant. The issue comes when I turn the outlet off. Once it's turned off and back on, it defaults the LEDs to the 'Demo' mode.

These LED lights are wired in Antiparallel which allows them to be animated in some way. I'm looking for a simple circuit I could put together in order to plug them into a USB adaptor and just have them constantly on until I turn off the outlet and vice versa.

From some basic prodding using my multimeter, I see the LEDs are drawing in between 3-3.3V. I had initially planned to hack the circuit that came with the lights but now I feel like creating my own might be better.

I'm very new to a lot of this stuff and only have some basic wiring and circuitry experience so any help is greatly appreciated. I feel like this is a small enough project I could tackle on my own. I've read some things about an ATTINY and using that, and I'm willing to learn more.

  • \$\begingroup\$ How many pins in the cable between the IR receiver and the LEDs? \$\endgroup\$
    – Ben Voigt
    Jan 28, 2022 at 23:08
  • \$\begingroup\$ use a cheap audio amp, pocket radio, or even the leads to a speaker from an old clock radio. Play static or a square/sine wave and feed that to the LEDs. A wall wort will plug that into your smart outlet, replacing batteries. \$\endgroup\$
    – dandavis
    Jan 29, 2022 at 9:28

1 Answer 1


I will take a SWAG. I did this with a white LED string that had 8 modes. If you connect the LEDs to a 5V DC power source,50% will light, reverse the polarity and the other 50% will light. Cautious the LEDs may require a little lower voltage. If this does not work the rest of this answer will not work.

To light them all there are two relative simple ways. You can use a motor bridge and reverse it at about 30 Khz and control the brightness with PWM.

To do without a controler try this. Connect the LEDs not the controller to a low voltage AC power source. I have a variable AC power supply I use that I start with about 3V and increase from there. You should reach a point where they will all be on at whatever brightness you select via the voltage input. At that point you know the AC voltage you need, you can use a AC wall wart to power them.


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