Every now and then we see some horrible pictures of people seriously injured after a sudden startup of motors during setup. Yeah, we all know that we should remove the props while setting up, but letś be honest: after the 10th time on the same night we get fed up and confident. That is when sh#t happens. Been there, done that...

I have seen some alternatives to removing the props, but this one is my favorite because it is quite simple and convenient: use a low amp 12v source instead of the battery. I am using a 1.5A 12v source that is enough to power the controler, but if any motor tries to start the voltage will drop and the controller resets. Even if it doesnt, 1.5A isnt enough to spin a prop to a point of hurting anyone.

It is simple because all you need is an adaptor (or solder your plug directly as I did). It is convenient because you problably have many low amp 12v lying around, and I actually prefer not to use my batteries so they stay fully charged to fly.

Do yourself a favor and just build one. :-)

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  • Wiki Ninja

    Great idea. What do you think about a generic inline 1-2A resettable circuit breaker? Solder it between XT60s or your power adapter of choice... Could work with any battery or wall supply, so you could easily take it to the field too. If it has a manual trip, you also have a switch that's easier than constant replugging of those tight power connectors.

  • Cool idea, thanks for posting!

  • My solution was, I had an old USB-mini cable where the mini side had shorted, and I spliced out the 4 wires from it. Strip the +5 and GND wire and solder it onto an old 2 pin header you have lying around, and instant USB power adapter! I hook it right into my phone charger, which has a 1.0A cutoff and sits at my desk :) If you want to run it through a regulator or BEC for extra security, be my guest, but the already regulated output from the charger sits at exactly 5.22V. And I have a USB battery pack for phone charging on the go, so I can take USB power to the field with me. It's great because USB is everywhere! On the occasion I forget to bring my USB battery pack, I can just plug it into my laptop directly, and I have never had a problem. Sure beats draining your flight packs! I have a picture of it here, hooked into a spare board I use solely for simulation:


  • I think i'll make one of these tonight, not so much out of safety for myself as safety for my batteries... I have actually managed to toast 2 lipos both on first use by overdischarge playing around with settings on the bench... Had no alarms back then
  • Graham, how would you solve that?  Perhaps a resistor bridging the output, like 10K would be enough?

  • Moderator

    Just check the open voltage of source before use, some have an open voltage of 18V+...

  • Thanks for posting this simple solution. I am also able to identify with the cartoon above and had a good chuckle.
  • Great Idea!

    I second that Mark!  I just hacked up three of them trying to find a barrel plug that would fit my stinkin' mini-PC motherboard.  So i have a few with no barrel plug to try out; because I didn't throw them away...absolutely not!

  • Brilliant - Great Idea!

    I will find a way to add this to the Wikis and the Safety sheet.

    The best ideas are often the simple ones.

  • Hahaha, that's looking like me, Mark :)

    I used to run a UBEC to a spare RC plug. The UBEC ran off a couple of cellphone batteries I soldered together into a 2s pack. Small and simple. 

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