Target Audience: Readers who do not have Eagle or are confused about using it.

You Need: Basic electronic schematic reading ability

It was time for an update and simplification!

I removed several ports not normally referenced in power connection discussions, relocated the previously marked 'Mystery Port' and relabeled it 'PM connection', moved some items around, and generally tried to make the diagram simpler.

Also added is the label 'Vcc 'ON'" to clearly indicate that the green LED6 is a power on indicator for Vcc present. It does NOT assure that Vcc is at specification. Only a voltmeter (DVM, etc) will do that.

I hope this can help someone to understand the power supply arrangement on the 2.5.x release.

Any errors on this drawing are my fault.

Click on the above picture or download it as an attached file.


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Thx, that is very useful. I already used your precious version of few months ago when i started with this hobby and it helped enormously.

Doug - that's great.

To finish simplifying, I would suggest just adding a Vcc carrot and listing in text below it the items powered in laymans terms ie 3.3V regulator, named Micro? etc and another 3.3V? carrot with the items listed under it in text such as the Data Flash that are powered by it. This helps make it clear the importance of good power to these important components.

Then get rid of the references to resistor sizes and part numbers that remain and other technical references that are meaningless to the majority of us.

I'm heading to the North Pacific today so am out of range for several months at a time.  I will check in when back in range.  Thanks for the great simplified functional schematic that most all of us can understand.  Will pick this up again when I return.   

Thanks! Can I draw the following conclusions:

  1. Snipping the red wire from the power module is the same as disconnecting JP1?
  2. Snipping the red wire would do nothing since the pin next to it is also Vcc?
  3. The input and output rails' V is isolated regardless of what JP1's status is?

Many thanks,



Are you using a 3DR Power Module?

The answers to your questions depends on this.

Vcc is the result after the D1 diode and F2 fuse. Before this, it is 5VDC.

Input/Output rails are isolated if no JP1. They are connected with JP1 by D1 and F2. 


Thanks Doug, yes I am using the 3DR power module. I'm using it on both my APMs.

For some reason, my servo's don't work if I don't have a servo cable connecting the input and output rails, regardless of JP1's status. I'm thinking I've blown something somewhere. Could it be because I was using the power module AND powering the input rail?

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