Frequently asked questions are about powering an APM2.5 or why the same does not work or why it has failed.
Here is a simplified schematic showing the major components of the 5V/Vcc circuit on the APM2.5
Target Audience: Readers who do not have Eagle or are confused about using it.
You Need: Basic electronic schematic reading ability
Note that I have separated the PWM Output section into the upper left corner with a heavy purple line that is bridged by the jumper JP1 on the APM2.5. This is to emphasize that diode D1 passes current through JP1 (and drops voltage). The remaining energy is then called 'Vcc'. Everything outside the purple corner is Vcc.
This is why the USB will power the APM2.5 when connected to a computer/USB hub. Note the fuse on the APM2.5 side of the USB connector AND another fuse on the output of D1. Another change from APM2.0 is the D4 6.0V Zener diode. If an over voltage is applied to the board, D4 will crowbar what it can to protect devices.
As with APM2.0, any 5V source connected to any of the indicated Vcc/5V points outside the purple corner (with GND of course) will power the APM2.5.
Also of note is the 'Mystery Port'. This port takes 5VDC before D1 and the fuse and is called 'JP_VCC'. Other clues to the mystery are the lines to 'ADC 12' and 'ADC 13'. A mystery indeed!
Any errors in this drawing from editing are mine.
I hope this can be used as reference for solving problems.
Thanks again for helping to clear up and simplify/de-mystify potential questions.
Thanks for posting this Doug!
I cannot connect any longer APM 2.5 to Mission Planner Board is recognised baud rate set ok but Times out
No Heat spmething message
I notice that the diode just above the IC2 socket has a small pin hole maybe blown yet seems ok with multimeter
any one with the full schematic
I think the ESC calibration caused this connect disconnect Lipo send spikes all over the board especially with jumper JP1 on it would be better to power the APM with a separate supply no ? Am I wrong??? help
The full schematic is available on the 3DR Store page. NOTE: V 2.52
You will need Eagle to view the *.brd and *.sch files.
The feature schematic is taken from the full schematic with minor modifications to help the 'flow' of the circuitry.
Doug, Thanks for clearing that up, obviously a language problem!
D4 is a 500mW 6v0 zenner across the board supply, presumably in the case of severe over-voltage it's supposed to blow the 500mA fuse, Not surprising the fuse won!
vitaly, Enough voltage present to blow the zenner, It could be that your board is fried!
That diode is not a vital component to the working of APM, more intended as an over voltage safety feature.
I would be very surprised if plugging in ESC's would have caused this! The APM is protected by not being connected to the raw voltage of the battery, The bec output should just rise to 5v0
Sorry was out...back now and still trying to get the board to work..
yes it is that diode there is a marking on it E 3.xxx cannot read the xxx as there is a pin hole
but looks ok if test with my Fluke as a diode should be I have version 2.5.1 board I have founf the schematic as well as v 2 I think you sent me the link.
I just cannot understand why?
could it be that I plugged the USB to my laptop at the same time as the ESC's and borad powered from the Lippo (with jumper Jp1 ON ?????)
I think the chip is ok it looked like a burn but was some flux on it....
it is actually diode D4
i could replace it but would diode stop the board to communicate via USB ???
The Zener is installed across the power supply to prevent damage to the board if you
a) connect too high of an input voltage
b) connect the power supply backwards
If either of these things happen the zener will conduct and the fuse will blow.