LED Power Supply Noise

The post title is slightly misleading because this is actually about an attempt to not have the LED strip from this post radiate noise into the environment. That’s simple enough, use a decent-quality linear power supply to drive it. However since I’m an empirical gnostic I wanted to check that there weren’t any problems, and got this.

Since that wasn’t coming from the linear PSU the next suspect in the vicinity after the LED room lights was the USB GaN power supply that runs various things that need USB power sitting right next to it. Luckily it was that and not something much harder to track down, and moving it just 10cm away and shuffling a few cable locations around gave this.

So the stuff in the first trace was purely noise from the USB power supply being coupled onto the cables from the linear supply. The lesson here is, along with anything bought from Aliexpress, check everything after you’ve set it up, don’t just assume that it’s working as it should be.

As an interesting data point, the usual suspects for radiated noise, overhead lighting, contributed nothing to the problem. These are good-quality LED downlights, IC4/IC-F rated so they’re embedded in a solid block of diecast aluminium all of which seem to have ensured that they don’t produce much if any noise.