All about drone guts

Note: This post was largely written a few weeks ago. It has good stuff in it, but it’s not current anymore. So don’t be surprised when(/if) I’ve made an incredible amount of progress between now and my next post!

I’ve continued to work on soldering. I now have the power distribution board (PDB) connected to the battery and one of the electronic speed controls (ESC). An ESC powers, and regulates the signals to, one of the motors that spin the rotors. So this seems like a good time to talk about the main components in the drone design.

Power distribution board (PDB)

The power distribution board accepts power from the battery, and provides it to all the other components in the drone. Each of the motors will be hooked up to this board through its ESC.

Electronic speed control (ESC)

The electronic speed control gets power from the PDB and instructions from the flight controller, and in turn powers and controls the motor it’s connected to.

Motor

Even if you don’t know how electric motors work (which, by the way, totally reasonable. I only have some idea. I think it’s magnets?) you probably know what they are. This motor receives power and instructions from its ESC and spins a propeller.

I’ll get into this more another time, but we want two of the motors to spin clockwise, and two to spin counterclockwise. Surprisingly, it doesn’t matter which motor wire you connect to which ESC wire. It’ll work however you wire it up. If it spins the wrong way, you just swap two of the wires, and it reverses direction. Magic!

Flight controller (FC)

The flight controller is the (pretty dumb) brains of the drone. It gets control input from the receiver, and figures out what the inputs mean in terms of how the motors should spin. It translates those inputs into instructions which it sends to the ESCs.

The FC also contains a couple of important sensors. It has a gyroscope so the drone can tell when it turns, and an accelerometer so it can tell when it moves. It also supports a number of other components, like GPS, and a camera, but I’m not using those right now.

Interestingly, the flight controller can be powered straight off one of the ESCs, instead of being hooked up directly to the PDB. This is one of many, many surprises I’ve encountered.

Instructions not included

You know how, when you got a Lego set as a kid, if you misplaced the instructions, you were basically lost? Or if you lose the instructions to your new IKEA cabinet, you will have no idea how to put it together? I have had a fun* time attempting to answer the question “so how do I actually connect this stuff?”. The FC, as you might imagine, is a very important component. (I mean, they’re all important; there really aren’t any optional components in this thing. I’m not even bothering with a camera yet. But it is the coordinator, so you need to know how to connect component to this flight controller.)

So I was miffed that there were absolutely no instructions in the kit on how to hook up the flight controller. Or, well, any of the electronics.

It took me days (of working on other things) to realize that the baggie the FC came in had ‘CC3D’ printed on it. Once I searched that online, I did find a reasonably good manual. The internet is a wondrous place, eh? Even with the manual, it took me a while to figure out how to plug in the next piece, the radio receiver (Rx).

Receiver (Rx)

The receiver is a chip which listens for instructions radioed to it, which it picks up with its antenna. (Aside: electronics are incredible. Remote communication? What? Yes, I know we’ve had radio communication for a century. That doesn’t make it mundane. We did not evolve to find this stuff intuitive. There’s so much for us to wonder at in the universe 😄.) The receiver passes these instructions on to the FC.

Transmitter (Tx)

The Rx communicates with the transmitter (Tx), which is usually, and in this case, a handhold remote control. It’s similar to a remote control car controller… but way more so.

The first prototype of the rocketdrone will definitely be using a handheld controller. Having the vehicle land itself is one of those problems I am deferring into the far future. But it occurs to me that if and when I do implement the autonomous landing functionality, I don’t have to calculate it onboard the vehicle. I could instead run that code on a separate computer which transmits instructions to the drone. This means the vehicle won’t need the extra computer onboard.

H(oo/ec)king up the receiver

(hooking/hecking) Yes, I’m rather pleased with myself 😁

The receiver is supposed to connect to the flight controller, passing along the instructions from the transmitter in the remote control, telling the vehicle how it’s supposed to be moving. This particular receiver has eight places to connect wires. So, which ones am I supposed to use?

Power and negative are easy, they’re 5V IN and GND (5 volts in, ground). I’m actually not sure which of the other terminals I’m supposed to use 😟. I’m not too worried about messing those up, though. Crossing those wires will only make things not work, it shouldn’t break anything.

Uh, whoops

I did manage to break the receiver chip, though 🙃. I’m not totally sure how? My best guesses are that I somehow mixed up the wires at some point, or that one of the shorts I definitely caused (though they were outside the chip itself, which I’ve been told should be safe? ¯\_(ツ)_/¯ ) was unsafe, and broke the chip. Or, most likely, when I was trying to power up the receiver chip to pair it with the transmitter, I connected the chip directly to the battery. Which proooobably overloaded it 🤦‍♀️.

At any rate, now when I plug the receiver to the flight controller in a way that I’m pretty sure is correct, part of the chip gets warm, which is promising, but neither of the LEDs light up, which is unpromising. I’m pretty sure the LEDs are supposed to light up when connected.

So I have more receiver chips on the way. Yay for breaking things!

My next post will probably be about my experience connecting and testing the components. Later!

Glossary

• PDB

  • Power distribution board

• ESC

  • Electronic speed control

• FC

  • Flight controller

• Rx

  • Radio receiver

• Tx

  • Radio transmitter