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Question - USB power vs ESC/Battery power or both

Posted by Mitch Robbins on October 23, 2010 at 2:31pm

Quick question regarding the APMega and Oilpan shield combination - can't see it clearly in the circuit diagrams.

Can power the combination with the usb connector for low current use such as programming without servos connected.

Can power from the board edge connectors with a 5v battery or ESC BEC.

Are there protections onboard for connecting the USB cable along with servos and a battery connected to prevent excessive current on the USB port?

What is the hardware fuse actually doing?

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Replies

  • FPVGenie February 15, 2011 at 7:38pm

    Wow. Just came across this thread. I have been, so fa connecting my ArduPilot Mega to the USB AND also connecting the BEC simultaneously. Had been doing this because the USB does not power the servos/RX and since I had no telemetry, I wanted to debug things on the computer thorugh USB.

    Not sure if I have already damaged something, but i figure I should not connect both power sources again ? and IF i do, then i need to hack the USB cable and remove the power from it ? 

     

    Thanks for confirming. If this is the case, i think its very important to know ! 

  • Ron Jacobs October 27, 2010 at 7:47am
    From Arducopter Manual:

    IMPORTANT WARNING!!! When you plug in the USB either disconnect your ESCs and motors or make sure your LiPo power battery is also connected. Otherwise you will blow your outputs.

    I think this only applies to Quads, but sounds like good practice, unless you have a modification that will prevent this.
  • John Hestness October 24, 2010 at 3:36pm
    I have been wondering the same thing. I saw a posting by a senior member that seemed to say that he did connect both USB and battery power at the same time. But for now I will disconnect the ESC, battery, and servos before I program, then disconnect the USB cable and reconnect the ESC, battery, and servos for software testing. Maybe there is a better way.

    Please post the results of your USB cable mod, if you do it. Thanks.
  • SciFly October 23, 2010 at 8:11pm
    The hardware fuse on the Ardupilot Mega board protects the IC's from overcurrent (>500mA). Im not exactly sure I understand your question but I wouldnt connect a battery or ESC or BEC in parallel with the USB, regardles of whether protection exists. I would instead desolder SJ1 on the APM board to disconnect the servo IN/OUT power bus from the USB port and IC power bus, then add a separate powersource (ESC,batt, etc) to the servo side. Alternatively you could accomplish the same (+have isolation =-)without removing the solder jump, if you put a DIY drones optoisolator inbetween the APM and the servos (preferred if you have the hardware, IMO).
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