I'm constantly loading and testing code and the power setup of the 2560 can be a bit of a pain. Mainly, the radio does not receive power because the Servo rails are only powered via a Lipo, which can be very dangerous. I never do anything but fly with a Lipo connected and I certainly don't connect one indoors. I'm just paranoid that way.


This hack will power the radio half of the servo rail with 5V from the APM's USB connection. The idea is to spilt the 5V rail into two halves. If you use an X-Acto knife you can easily cut the trace connecting both sides. I cut the ground rail in half as well, then used some solder to repair the bridge. Then I connected the 5v from the APM to the input side as indicated below. Now I can power the radio with the USB.


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Comment by Jason Short on December 14, 2011 at 5:47pm

Arrgh, I will update that.


Comment by Rob_Lefebvre on December 14, 2011 at 5:57pm

At the same time, you might want to update that JP1 *must* be unsoldered.  I don't think that's mentioned.

Comment by John Campen on January 21, 2012 at 1:39am

This hack works a dream Saves a lot of switching around of wires etc,

Glenn maybe your confused by the numbering of the pins. On the older APMs boards the first pin was numbered 0 then through to 7 which is the eight pins for in put and eight pins for output on each side. The newer APMs the first pin is now numbered 1 then through to 8. Just make sure the cut is exactly in the middle of the 8 pins on each side which ever the numbering is.

Comment by Glenn M on January 21, 2012 at 1:42am

When I posted the pic was wrong, but it has since been fixed :) Will be performing this hack on mine soon.

Comment by Søren Kuula on January 29, 2012 at 7:32pm

Hi, not quite the same topic but related: How can it be that my APM1 does not power up or light any LEDs when powered from the BLCs when my friend's one does?

It runs OK when connected to, and presumably also powered from USB.

5V output from the BLC was verified with a meter, is OK. Also the plugs the correct way around (under both BLC and US power it will start its motors).

In the schematic (APM, not the oilpan), I see 4 different nodes with power on: +5V, +5V!, Vcc and JP17 Pin 2. I wonder which one is the USB one?

Both my own board and my friend's were bought completely assembled. Could there be a jumper wire somewhere that was omitted on mine? Is there a regulator between BLC power (which might really be 6V or more from some BLCs) and +5V?



3D Robotics
Comment by Chris Anderson on January 29, 2012 at 8:35pm

Soren: This is covered in the Troubleshooting guide.

Comment by Søren Kuula on January 30, 2012 at 2:48am

Hi Chris,

Thanks a lot, that did it. I wonder why my board was not "factory default".... There was no sign that it was ever soldered. Well anyway it works now.



Comment by Dave on February 6, 2012 at 11:46pm

Before I do this mod, just wanted to clarify a couple of things:

1. Does SJ1 need to be unsoldered?

2. Can the entire board be powered from the ESCs after the mod or is a separate BEC required?

Comment by John Campen on February 7, 2012 at 1:36am

where is SJ1? I did this mod Dave and didn't unsolder anything. Just make sure you do the clean cut of the copper trace between input and out put side. I was using the ESC power and it worked fine but now I'm using a separate switching 5v 3amp regulator power supply. 

Comment by Dave on February 7, 2012 at 3:41am

SJ1 is the link to remove if powering the APM from an external battery - I thought perhaps that's what Robert was referring to above.

Thanks for the info.  I'll give it a go.


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