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Wemos D1 Mini random PCB thickness

If you order a “Wemos D1 Mini” you’d expect to get the same thing every time, right?


The Wemos brand has become a victim of counterfeiters, who make a near-exact copy of the board and then produce it as cheaply as they can. These two D1 Minis look superficially similar, and if they were lying on the bench you would probably have trouble telling them apart:

But look closer. The shape of the PCB is slightly different around the top edges, and the silkscreen is slightly different. It’s most obvious around the “5V” label near the bottom left. There’s also slightly different soldermask pullback around the pads. The board on the left has several parts out of alignment, although electrically they’re still connected and the board works fine.

Part of reducing the cost is to use whatever is the cheapest PCB substrate they can get their hands on at the time. These D1 Minis were made using totally different PCB material:

One PCB is 1mm thick, and the other is 1.6mm.

I’ve seen D1 Minis with 0.8mm, 1.0mm, 1.2mm, 1.4mm, and 1.6mm PCBs! You really can’t predict what you’re going to get.

Why does this matter?

Most of the time, it doesn’t. But recently I heard from someone trying to build my Air Quality Sensor project that their D1 Mini wouldn’t fit in the 3D printed case, because the case only allows PCBs up to 1.2mm thick! Oops.

So I’ve now generated STLs for both 1.2mm and 1.6mm slots, for both the “Basic” and “Display” versions of the case. You can grab the latest STLs from the product pages, linked from the respective episodes:

3 thoughts on “Wemos D1 Mini random PCB thickness

  1. Jonathan, I also fell victim to the counterfeit Wemos D1 Mini and I had actually a bigger issue. It seems that the USB flash chip is slightly different and does not work on Mac OS. So I could flash them only on Windows.
    There is also a visible difference: On my counterfeit Wemos D1 Mini on the PCB it is printed “mini” whereas the originals say “D1 mini”. Do you have the same difference?
    By the way, I love your build instructions for the air quality sensor. We also have build instructions for one with the same PM sensor but also includes CO2 and Temperature and Humidity.

  2. All the ones I’ve seen use something in the CH340 family (Nanjing Qinheng Microelectronics) as the USB-serial chip, including the genuine ones. I’ve never seen one with a FTDI chip or anything like that.

    Getting the driver to work on MacOS requires a little mucking around, and there are certain driver versions that will cause a certain kernel panic on certain MacOS versions. But once installed it does the job fine.

  3. Thanks for the update, My D1 Mini’s are still on their way and I was about to start printing some cases today. Well timed.

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