[Solved] MD30C ground connection

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[Solved] MD30C ground connection

Postby Adrare » Mon Apr 09, 2018 10:26 pm

I read on a post here that that grounds are commoned on the board MD30C; on the R2 I just received, it seems (according to my ohmmeter) that there is a diode between the minus power pin and the Gnd pin of the ext PWM connector (JP6 being on ext position); the cathode seems to be on the power side, anode on the PWM connector side. So my questions are:
1/ how is the Gnd interconnection made, would you have a sketch of it ?
2/ Can you confirm that there is a diode ? If yes, which type is it ?
2/ I'd like to put a 0.05R resistor in order to measure the current in the motor and prevent from overload :idea: ; this resistor should be seen by an analog port of the MCU (PIC18F), referenced to ground. Where do you suggest I should place it in the power circuit ? I'm confused with this diode between the 2 Ground... :?
Thanks a lot in advance,
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Re: MD30C ground connection

Postby waiweng83 » Tue Apr 10, 2018 2:12 pm


There is a MOSFET in between the system GND and the negative terminal.
This MOSFET is used for reverse polarity protection.
When the board is power up, the MOSFET is turned on and system GND is connected to the negative terminal.

To add a shunt resistor for current measurement, you can connect it in between the negative terminal and the GND of your MCU.
Do not connect the GND on the input port to your MCU Gnd. Just leave it disconnected.
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Re: MD30C ground connection

Postby Adrare » Sun May 06, 2018 1:21 am

Thanks for your answer and sorry for my late one.
I had problems with my shunt resistor, the current was measured as negative !
Everything works fine now.
Thanks again ;-)
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