Arduino UNO + DK Motorshield + 2x 12V fans |12V DC 3A psu safe?

Hey guys,

I am a total newbie in the world of Arduino, so bare with me please. I've been trying to build a simple project based on a Youtube-series. I'm using the UNO + Motorshield to power and control 2 PC fans that are managed via a custom software program (Simhub).

The project has the following components:

  • Geekcreit R3 UNO
  • DK Electronics Motor shield
  • 2x 12V 4000RPM pc fans
  • 12V 3A PSU

The fans have the following specs:

  • 4500 RPM
  • 1.52 Current (A)
  • 12V (DC)
  • 18.24 Power (W)

The builder in the Youtube clips suggests using a 12V 3A psu. So I first tested the psu out on my UNO to see if it worked. It sure did, but about 1 minute later the main fuse popped on the UNO and the board is in limbo. I had the UNO connected via USB as well, so I'm guessing that wasn't the smartest move on my part.

After getting a new UNO I rebuild the boards and tested everything out with a 12V 500mA connected to the ext power supply of the motorshield. Hoorah, 1 fan works! It only blows very lightly but it works. The 2nd fan doesn't want to activate on any of the M2/M3/M4 slots. I suppose this is because of the low amps of the psu (500mA)?

Now I want test out the 12V 3A psu on the motorshield, but I'm scared to blow that one up as well. I connected it for 3 seconds I instantly heard a 'sizzling' sound and the smell of burning electronics. I disconnected it immediately and tried it out again with the 500mA psu and luckily it stills works.

So... My question to you experienced UNO builders is: is it safe to connect a 12V 3A PSU to the DK motorshield? Or is this too much? And what PSU would you guys recommend to power the 2 fans? I don't need them to be working at 100% full power, but somewhere around 80% of their capacity would be nice.


We can help you but more information is needed on this end. Post a schematic, not a frizzy thing and include links to technical information on all the hardware items. Posting your code will also help.

Hey gilshultz,

Thanks for the reply. I adjusted my post to make it a bit more clear and to report the next issue.

The problem with the fans not working has been solved. Turns out that there was something weird going on with the polarity. After using a 12V DC female plug to connect an external psu, the fans started working. Now I need to know what's a safe external psu to connect to the motorshield :slight_smile:

@dwdxd, your topic has been moved to a more suitable location on the forum.

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