PicoBuck not working

Components & Accessories
1

Hello,

I purchased three PicoBuck driver boards to drive nine groups of high-power 3W LEDs, where each LED group consists of four LEDs connected in series.

I contacted technical support because two of the boards aren’t working. I was asked to create a thread, which I’m doing here.

My question isn’t really technical—since using the PicoBuck boards is straightforward—but rather a customer service issue: what happens when you receive components that don’t work?

Problem description

For testing, the three PicoBuck boards are powered by 24V, the control inputs are not connected (so regulation occurs without a control signal), and the outputs are connected to the LED groups.

I’ve found that I have two boards that aren’t working:

  • PicoBuck1: Channel 1 OK, Channel 2 OK, Channel 3 appears to have no regulation (output always 24V) —resulting in one LED burning out every time it’s powered on (I’ve already killed four).
  • PicoBuck2: Channel 1 OK, Channel 2 has zero V output, Channel 3 OK.
  • PicoBuck3: All three channels are working correctly.

I’m considering the following solutions:

  1. SparkFun sends me replacement parts for the defective components :slight_smile:

  2. I buy another PicoBuck board and replace the two defective channels with two channels from the new board. The downside is that I don’t have much space to fit a fourth PicoBuck

  3. I buy two more PicoBuck boards and replace the two defective boards, hoping that the new boards will work properly

To give you an idea of my prototype, I’m sending you a photo of the front panel showing the nine groups of LEDs connected in series, and a second photo showing the connections of the three PicoBucks

20260706_114449
20260706_1144491920×3412 1.13 MB

apparently only allowed to send one image :open_mouth:

2

It depends on the situation but in general it’s very unlikely 2 of 3 were defective so a referral to troubleshooting here usually makes more sense…

It only allows one photo on a first post, you should be able to add more now

The top unit is the one working correctly, right? The other 2 appear to have flux or similar between some of their output pins…can you use some IPA and try getting all of that shiny stuff off entirely and re-probe the outputs?

3

To answer your question, yes, the only PicoBuck that works is the one at the top.

The one in the middle has only 2 out of 3 channels working. The center channel doesn’t work (no voltage). To verify this, I desoldered channels 2 and 3 and swapped their connections to check that the connections to the diodes of middle group were correct. After swapping them, the diodes connected to the center channel still didn’t light up, so I conclude that this channel isn’t working.

As for the bottom one, the voltage regulation on one of the three channels does not seems to be working. If I connect the group of four diodes in series to this channel, one of the 4 diodes in series consistently burns out. If I bypass the just burned-out diode, the buck converter should automatically adjust the voltage for the three remaining diodes, but in practice another diode burns out. So I conclude that the voltage regulation is not working.

Sorry to bother you with my problems. I think the best solution is for me to buy two more buck converters, since the solution I had considered—adding a fourth PicoBuck—isn’t possible due to space constraints.

20260709_110444
20260709_1104441440×2560 904 KB

20260709_111254
20260709_1112541920×3412 1.14 MB

4

We do sell these as well FemtoBuck LED Driver - SparkFun Electronics

5

Hi @DrCoolZic ,

Can you share a link or datasheet for your LEDs? By default, the PicoBuck will try to drive your LEDs at 330mA. Are they rated for that current?

I hope this helps,
Paul

6

For the 8 peripherals groups the LED are 1W 350 mA and the central group are 3 W 700 mA as I intend to strap the PicoBuck for this group.