I'm planning to make a micro/nano quadcopter and I've bought all major components so far. The only thing that I can't figure out are motor drivers. I was planning to use some kind of transistor to do that for me (motors are 3.7V @ 1.5A marked). So I was wondering if that is a good idea? No commercial drivers can fit since it needs to be lightweight and I have 4 motors that need to be driven separately.

  • \$\begingroup\$ How do you plan to control the speed? Radio link? Trailing wire? \$\endgroup\$ – WhatRoughBeast Feb 12 '16 at 17:53
  • \$\begingroup\$ Nope, i will use arduino as a controller, and i will control arduino through NRF24l01 wireless module. That is why i need 2A transistor since arduino can provide 50mA on its outputs. \$\endgroup\$ – Instrukcije MatematikaOS Feb 12 '16 at 18:22
  • \$\begingroup\$ The typical solution for a micro/nano quad is a good surface mount logic level FET operating as a low side switch (ie, connected in the negative line of the motor) and with a pulldown resistor on the gate. The DMN2041L is commonly used to "upgrade" toys made with marginal FETs so could be a good place to start for a custom effort. \$\endgroup\$ – Chris Stratton Apr 14 '16 at 17:36

You will need to make your own bi-directional discrete H bridge (if you want to drive propellers in both directions) or a half bridge if you want only one direction.

Don't get 2A transistors, get something like 8-10A rated MOSFETs and ensure your design can survive inductive loads and over-voltage spikes from the motors. Do the proper research into H bridge motor driving and see some example designs.

You can get "complementary" N and P Channel MOSFETs in nice little SOIC-8 packages or perhaps DIP-8 which are rated for the 8-10A I suggested. Use these to make nice compact motor drivers for each of your motors.

Make sure the transistors are "logic level gate drive" meaning they turn on/off with only 1-2 volts.

You are right that there are not many commercially available modules or packages easily purchasable for this use. You'll find there are some nice integrated ICs that can do what you want though, they are just large (usually 20+ pins) and will not fit well on your nano-copter design.

I expect you'll need to make a PCB to hold the driver.

  • \$\begingroup\$ Just put a diode on the NPN to solve your overcurrent problems (make sure you get the right one and read up on it), you don't need to oversize your mosfet. Throwing margin on a design is not a good way to solve problems. \$\endgroup\$ – Voltage Spike Feb 12 '16 at 22:12
  • \$\begingroup\$ no @laptop2d, that is not the reason why I said to use a 8-10A FET rather than a 2A one. It's because the ratings on the devices are under certain conditions, and are useful more as a constant "on" current. When switching, the Rds_on is important to have low, which results in a higher "rating" being listed for the component. \$\endgroup\$ – KyranF Feb 13 '16 at 1:04
  • \$\begingroup\$ @laptop2d Also how will a diode solve overcurrent? I don't think you know what you are talking about.. All the diode will do is drop approx .7V (depending what diode it is) and will not really help as you can easily short circuit hundreds of amps through a diode. No overcurrent protection. \$\endgroup\$ – KyranF Feb 13 '16 at 1:05

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