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I am building a drone to understand more about the associated electronics and operation. I am using this guide as reference.

My drone is basically the same, but I replaced the SI2302 N-channel MOSFET with the IRF730 N-channel MOSFET due to availability. Both of the components have similar values such as drain-source voltage, gate-source voltage, and continuous drain current.

When I check continuity between the positive wire of a motor with the negative wire of another motor I get a true value. But I think that is wrong! Could you explain if that is correct or if I failed in my PCB connections (I verified almost every soldered point, checked the MOSFETs, but I do not really understand MOSFETs)?

The schematic is this and I show my measured points:

enter image description here

My drone is this:

enter image description here

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  • \$\begingroup\$ The schematic is badly wrong around the MOSFETs (diode in the wrong place), the MOSFET symbol is upside down and it is the MOSFET symbol for a P-channel MOSFET when it should be an n-channel MOSFET symbol. Where did this erroneous schematic come from? \$\endgroup\$
    – Andy aka
    Commented Jan 3, 2023 at 21:07
  • \$\begingroup\$ It comes from the reference link posted, thank you for your comments, so I will try to research for another proposes about the controlling of a motor with n channel mosfet \$\endgroup\$
    – imt_blake
    Commented Jan 3, 2023 at 21:33
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    \$\begingroup\$ The continuity you measured is due to the motor acting as a low resistance. If you want to know how to activate a motor with an n-channel MOSFET, there are plenty of answers to that on this site plus, if you don't understand something, raise a new question asking about the information you found. However, the circuit you show is totally wrong in the connection method but, your question was about continuity and yes, your measurement will show continuity. \$\endgroup\$
    – Andy aka
    Commented Jan 3, 2023 at 21:51
  • \$\begingroup\$ Whereas the schematic symbol is indeed flipped, if you still connected Source to Ground (as also indicated in the schematic) your circuit will be fine \$\endgroup\$
    – Ken Grimes
    Commented Jan 4, 2023 at 15:32
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    \$\begingroup\$ There should be capacitors across each motor's terminals and reverse biased diode from every output MOSFET's drain to at least +supply. (Not sure the step-up converter is serving something useful: Check the PICO's documentation about power supply options.) \$\endgroup\$
    – greybeard
    Commented Jan 4, 2023 at 16:18

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The measurement is correct, what you're measuring is the electric continuity across your motor M2. In your electric motors (brushed DC) you have the following

Brushed DC motor source: https://www.toollogic.com/brushless-vs-brushed-drills/

From left to right: The current comes prom "+" wire, through the brushes and commutator goes to a series of winding. simplifying the wiring part you have a coil like this:

One winding source: https://uav.jreyn.net/quadcopter-design/step-5-motor-selection

So when your multimeter applies some DC voltage, a DC current flows through the windings, meaning electric continuity.

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