Destroyed two Pololu at setup


I bought a Pololu A-Star 32U4 Mini SV, Pololu A-Star 32U4 Micro and a 5V up/down stepper (D24V22F5).
I installed them on a Breadboard and connected VIN of al three items to to12V. On both Pololu the led starts blinking. when I connect usb to programm the Pololus both of them get hot and stop working.
The only additional item I connected was a neo_pixel. Neo_Pixel was connected to 5V output of the 5v downstepper, ground to common ground and the DIN to one Port of the Pololu.
Is there a known Issue with connecting usb and VIN at the same time?

I ordered the Items again but I just would like to know what went wrong? It is not in my mind to destroy the new one again.

Greetings Johannes

Hello, Johannes.

I would not expect connecting USB to those A-Star boards while they are powered from the VIN pin to damage them like that.

Could you post more information about your setup? Some pictures of your system that show all of your connections might be the most helpful. Did you have everything connected (e.g. the regulator and NeoPixels too) when you applied power and plugged in the USB? Is there any visual damage to the A-Star 32U4 boards? If so, can you post some close-up pictures of the boards showing the damage?


Hello Brandon,

the good messages is, the Pololu A-Star 32U4 Micro has survived.
To test it I used the Arduino for atmel studio plugin from Visual Micro. After Compiling the “Blinking.ino” and doing the Upload to Pololu the Led was not blinking. I thougt it was destroyed. Then I tried he Arduino IDE and then Led was blinking. So I am relieved. So I tested on with the Setup: VIN pololu and 5V Downstepper = 12V, USB Connected and neopixel connected to Port 12 and to 5v Downstepper + ground. Every thing works fine.
The Pololu A-Star 32U4 Mini SV is definitely destroyed. When I connect VIN to 12v the onboard 32U4 gets very hot you can not touch it. There is no visual damage to the board.

I will try to make a image of the setup.

Thanks Johannes

I am glad the A-Star 32U4 Micro survived! When you have time, I would still be interested in pictures of your setup to see if there is some indication of what might have damaged the A-Star 32U4 Mini.



I hope you can see the image.

this is my setup.
After setting up I corrected one error. I didn’t use a resistor between the neo_pixel and the port. I quickly corrected this.

Meanwhile I received the new mini and until now everything works fine.

Johannes Krijger

I do not see any problems with how you are connecting everything. It is hard to tell from the angle of the picture, but it looks like some of your solder joints could use a little more solder. For example, if you can see any of them that look like the one on the far right in the image below, you should probably touch them up a bit so they look like the ones labeled “Good”:


Hello Brandon,

thank you for advise.

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