Frequently asked questions are about powering an APM2.0 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 APM2.0
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 APM2.0. 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 APM2.0 when connected to a computer/USB hub. Note the fuse on the APM2.0 side of the USB connector. In fact, any 5V source connected to any of the indicated Vcc/5V points outside the purple corner (with GND of course) will power the APM2.0.
Any errors in this drawing from editing are mine.
I hope this can be used as reference for solving problems.
-=Doug
Replies
Doug
Thanks for taking the time to do this. Very helpful to see what is going on with the power.
Bob
Thanks for posting this Doug!
Robert,
The two diodes are the same family but definitely not the same device.
APM2.5 uses MBR120VLSFT1, 1A 20V Schottky. Voltage drop = 0.203 to 0.300 (varies with forward current)
APM2.0 uses RB751S-40 (type), 200mA 40V Schottky. Voltage drop = 0.37 (at 1mA)
Essentially the APM2.5 got an upgraded device. I was surprised to see the forward current so low. Lets me know not to push the limits with it. They must have had some APM2.0 returns with the diode open.
-=Doug
Betcha lunch that there isn't 0.2V difference if they are not the same component.
-=Doug
Thanks, this will be helpful for people. I'm curious to know if the diode being used on the APM2.5 is the same as the 2.0, or if there are any components that are different between the two, as regards to power flow between the output rail and the input rail. I haven't looked myself.