Trying to repair a Redpawz R020

[il_mix]

Hi, everyone!

Just joined the forum to look for hint to repair a Redpawz R020 drone.

I've recently found this drone in the woods. I've brought it home. No battery charger, no controller, no rotor shields.
Before spending any amount of money in spare parts (at least a battery charger), I would like to know if it is worth to try to revive the thing.

I made several test yesterday:
- recharged the batteries with a lab power supply => the drone turned on
- connected via WiFi to the drone with my phone, and tested the camera using the HTS UFO app => can connect to the drone and see the images => the main processor works
- tried to control the drone with the app (I haven't yet understood if I actually can control this drone with the app...) => no motor movement
- tried to power the motors directly to see if they spin => all 4 motors spin when manually powered

So, why is it not working?
2 main hypotheses:
1) I actually can't control the drone via app
2) there's some problems in the "signal route" between the main processor and the motors

Regarding point (1), the question is quite easy: does anyone know if I can control this specific drone model via WiFi?

Point (2) is more complicated. But the short answer is: shure there are some problems!
I've disassembled the drone and noticed that there are 4 SMD components just before the motors output wires, and 3 of them are noticeably fused (see attached image). No wonder they won't spin... Fourth one looks ok, but maybe it is just less damaged.
The problem is that I can't understand what these components are. They are 3 pins SMD. From the not blown one I can read something like "XORR" or "XORB", with what looks like a "22" written vertically. Couldn't find any info on the web.
I really don't know anything about drone (and motors in general) electronics, but maybe you can tell me which components are typically put before the motors. I suppose it could be a transistor that feeds the current form the battery when the processor sends out a PWM (processors pins have typically low current outputs and can't power a motor). Sounds reasonable? What could I use to replace these ones?

My next test will be to measure (with an oscilloscope) what the processor sends to these components, to see if the signals changes (or at least something arrives) when playing with the app.

Many thanks for all the hints you'll give me!

-- EDIT --
Weel, while writing this thread, and realizing these components could be transistor, I've found this:

500 - INTERNAL ERROR

www.transistormosfet.com

Sounds good...
Doubt I will find any datasheet for these, anyway. If someone have hints on the specs for alternatives I'll be thankful!

 

[wafflejock]

If you look at a "flight stack" on racedayquads.com or getfpv.com it is a "flight controller" or FC and a "electronic speed controller" or ESC. Basically these are the two electronic components used to get a quad flying.

1. The flight controller takes input from some sort of receiver (you could buy a Taranis/FrSky or Spektrum/DSMX recevier for around $20)
2. The receiver gets input from some sort of transmitter/controller (example Taranis QX7 or Jumper T16 around $120)
3. The receiver passes along the signal to the FC or flight controller which is the "brains" and has the primary MCU for the quad (generally a STM32F4 or STM32F7 processor) and has a inertial measurement unit or IMU on board (like MPU9250 or MPU6000/6050) so it has accelerometer/gyro data and can tell what direction it's rotating and what level is for auto-level mode.
   The receiver has a separate "channel" for each signal input, throttle, aileron, rudder, and elevator are typically the channels, but the FC takes in that data and uses it's own gyro data to compute the output signal to the ESCs.
4. The FC sends along a signal to ESCs, it could be simply a PWM signal but is usually a higher speed digital signal like DSHOT600 or DSHOT1200.
5. ESCs get a throttle input that gets translated to 0-100 basically and they control power to the motors.
   There are broadly two kinds of motors used in quadcopters, brushed and brushless.

It appears your dealing with brushed DC motors not brushless, easy way to tell is brushed will have only two wires coming out, brushless will have 3 wires coming out.

If this is just brushed motors you can search for "AIO brushed FC" and find replacement boards that have receiver built in and all (I know betafpv makes these I think around $60). Then would just need to "invest" in a transmitter (suggest the T16 but a few good ones out there just search for reviews/prices)

 

[wafflejock]

Oh also they do look like transistors to me, basically an "H-bridge" circuit can control DC brushed motors and vary the speed of the motors (by controlling the current flow). With brushless motors they work by the ESCs having MOSFETs that get opened and closed in quick succession to keep the motor turning along, so there are basically three coils of wire in the BLDC motor and the ESC handles speeding up or slowing down the opening of the MOSFET gates to get the motor moving.

 

[wafflejock]

Also also before @Dugdog47 comes and writes it you will be better off with brushless motors in the longer term if you decide to get into building quads as a hobby too, they fly much better, and won't burn out (basically ever, just bearings could wear out but usually knock a magnet loose or otherwise damage the bell/windings before the bearing wears down). The brushed motors will die in about 6 hours of runtime.