It so happened that because of his stupid mistake in one of the summer days I brought inoperable your drone.
On this day it was very windy. Nevertheless, I decided to run.
I found a large open space down the drone to the ground and began to take off.
I picked up the drone for a couple of meters into the air. But at this time a strong wind blew and carried me from the drone. As a result, he hit a tree and fell to the ground ...
What is the problem?
Before I could fix your drone, I had to find the root of the problem. One motor is not working. But why?
I started with the fact that carefully unscrewed all the screws to open the housing.
When I opened the body, I immediately got a pleasant surprise. Do you see it?
One of the wires of the motor that does not work, hung in the air!
Wow, I could not believe that it would be so easy.
"Now I can just quickly solder wireAnd all will be well "- I thought.
Unfortunately, it turned out to be more difficult ...
I resolder wire and connect the battery. Even without including the power button, the motor that I "repaired", he began to spin like crazy.
Strategy electronics repair
It turned out that "hanging in the air wire" was not a problem. No, certainly, it was one of the problems, but soldering did not fix my drone.
What to do next?
A further useful to my rewarding experience working with electronics ...
When I create from scratch a new electronic device, it is 4 out of 5 just does not work on the first try. One of my strategies for troubleshooting in this case is to measure the voltage on the board.
From my scheme I choose the important points in the circuit that I need to check. Two obvious moment to check - is the Vcc (plus) and the ground (negative in most cases).
Other important points in the circuit depends on the circuit. But it may be, for example, the value of the control signal on the base of the transistor, the output terminal of the integrated circuit and the state of t. D.
Unfortunately, often electronics manufacturers do not provide the concept of its products to the end user. I, for example, there was no concept for the drone.
Although I had three working motor. By measuring the voltage at the terminals of these engines, I would have known what to expect from the inoperative engine.
Debugging motor
The engine runs, you need to sue him stress. So? So.
Since the power button is turned off, the engines do not work. I measured the voltage, and operating engines have the same voltage level as the "plus connection" on both wires, so they did not work.
I then measured the voltage at engine idle (which worked at full speed), and found that a wire (which is hung air), now had a voltage of 0 volts. While other wire had the same voltage as the plus compound.
It was like two motor connection wires directly to the power supply. Not surprisingly, the motor runs at full speed!
Testing for troubleshooting
I continued to search for the real problem. The voltage on one of the wires of the engine problem was 0, but it was supposed to match the voltage of the "plus". Why?
Some of the ideas that I put forward then were as follows:
- Maybe there is a problem with the calibration, which makes the rotation of the motor is very fast?
- Maybe there is a problem with the electronics controlling the engine?
I quickly ruled out the theory of calibration. The motor rotates even when the power switch was turned off. I did not see how it could be related to calibration.
A very common method of control brush DC motor is the use of a MOS transistor. So, I made a simple circuit diagram for this:
Assuming that the motor control my drone was developed as described above, I could think of two potential problems:
- The transistor was broken
- Pull-down resistor on the base / gate has been "shorted"
Before I could continue to examine these theories, I had to confirm that the scheme, which I drew up, was correct.
For this I used a tester function "continuity" on your multimeter to determine which components are connected to the engine. I quickly discovered that the problem of the engine wire is connected to an integrated circuit with the marking "9926".
I googled around and found the necessary "datasheet". Turns out it was a MOSFET-transistor. And I could see that he was connected as my scheme above. Hurrah!
I then, using a function of its continuity tester, found that 100% has been a short circuit.
One of my theories is that the resistor connected between the gate and the ground is broken. Because it was the most simple theory to test, I soldered the resistor and measured again.
But! It was still a short-circuit!
This can only mean that the MOSFET-transistor was broken.
I ordered this transistor. Vypayal old and solder the new one.
Hurrah!
Drone running again !!
Main conclusions
- First, find out what is not working. In my case, it was easily one of the engines was not working.
- Next, find out why it's not working. This is the tricky part. Try to find a scheme to what you want to repair. Use a multimeter to measure voltages in general and search suspicious stresses in particular.
- From what you have learned, create theories about what is causing the problem. Check those theories that the easiest way to check first. Continue until you find the problem.
- Next correct the problem. Sometimes you are lucky, and you only need to solder a wire that went away. In other cases, you need to replace the small and difficult component.