Automation 2040W Mini only runs when plugged into USB


I have an Automation 2040 W Mini board plugged into a 24V power supply via it’s +/- terminals. When powered via that I only get the power LED lit up, nothing else. I have loaded a working script onto the board and named it but it will only run that script when I plug in a USB cable too.

When running it on the 24V supply, the only light is the power light. Whereas as soon as I plug USB in to the board the relay light comes on, shortly after that the Wifi light kicks in (as-per my script). Likewise, as soon as I remove the USB cable it reverts to only having the power light lit up.

Connected to the board itself are a BME 688 via the QW/ST port, a DHT22 via the 3V3, GP0 and - pins and a 24V fan on output 1 and the - terminals.

What am I missing here, as I believe the board should be able to run purely via the external 24V supply, right?

I’m running the latest Pimoroni Micropython release (1.19.18) and my script isn’t has no issues when the USB is connected.

Any help or pointers would really be appreciated.

If you have a voltmeter, check for +5V on VBUS when powered via the + - terminals.
I’m not seeing where the Buck Converter +5V connects to VBUS on the schematic?
automation2040mini.sch (

Yeah, so with the 24V input and USB plugged in I see 5.5V on VBUS and VSYS and with just the 24V input it is 0V so that’ll be the issue.

Do you know if this was by design because all of the documentation indicates it should work. I think I could work around it by taking the 5V output from the Automation and feeding it back into VBUS, it’s a little hacky but I think it’ll work.

I have no idea if this was by design? Seems an oversight to me! The buck converter has a current limit you may want to keep in mind. 300ma if I read the schematic correctly, which isn’t much IMHO.
Just curios as to why your using the 24 PS? Assuming you have a spare USB C supply, that may be the way to go?

It’s driving a 24V fan via the outputs, I was hoping to get away with just the one power supply for the whole thing.

Figured it was something like that but had to ask.

For any folks who stumble over this in the future. It looks like I had a faulty board. I reached out to support and they sent out a new one which worked perfectly.

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Thats good to know. Bummer your board had a fault, but now you can do it the way you wanted in the first place.