I’ve been slowly collecting parts for a new quadcopter – by slowly, I mean for over a year; each time I spot something better designed, I’ve been buying them – for me design incorporates not just engineering but also elegance. I finally have all the parts I need to start building, and since I’m starting from scratch, I thought it worth blogging my progress – “Build Your Own Autonomous Quadcopter – BOM (Bill of Materials), Assembly and Testing. You can follow my progress by searching for the tag “BYOAQ-BAT”.
WARNING: This series of articles describes how I am putting together my new autonomous quadcopter. They are not a set of instructions which, if followed, will result in a working, remote controlled quadcopter. They won’t. What you will end up with is a piece of machinery that spins blades around all by itself hacking to pieces anything in its path. I have deliberately omitted the very low level details from this set of articles for that reason. If you do choose to use these articles as though there were a set of detailed instructions, any resultant damage, death or destruction is entirely your own fault. You have been warned.
On the flip side, if you are building your own quadcopter, with either autonomous or human control, I hope you’ll find things here that are interesting and useful to you.
First, PCBs and electronic components. Here’s the PCB, as produced by Ragworm from the Eagle beret.brd board file up on GitHub. It’s essentially just a breadboard, with just a few minor tweaks to fit some very specific requirements of my new quadcopter.
When soldering components to PCBs, I find it’s best if you add the smallest things first, and build upwards. The first step then is to add the wires; I’d worked out the wiring beforehand on a print out of the top-side of the Eagle board. With all the wires in place, I sellotape them down before flipping the board and soldering them to the board.
Once the wires are soldered in place, next step is to add the smaller components – this time I hold them in place with blue-tak while I solder them on:
- a 100k pull down resistor
- a MOSFET
- IDT pins for the IMU breakout
- IDT pins for the ESC connections
Next comes the 40 pin IDC connector joining it to the PCB. At this stage, I fix the beret HAT board PCB to the A+ (no power and no SD card) while soldering on the connector to ensure positioning is perfect.
Next step is to add the wires and connector that will eventually attach to the heater resistor. It should now look like below. All that’s missing is the IMU; but before I attach that, I like to test the various points on the board. Without an SD card, you can power up your A+ with the beret plugged in and then power will make it through the GPIO pins to the PCB to allow you to do the testing with a multimeter. I check that there’s 5V where I expect it, and zero resistance between connected rows / columns where I expect.
Prior to attaching the IMU to the pins on the PCB, there’s a few bits and bobs to do with the IMU breakout board. It supports both I2C and SPI, and allow option pull-up resistors to be used, and if using I2C, the I2C addresses may be selected. These are all done by soldering bridges between clearly marked contacts on the breakout PCB. Since the Raspberry Pi I2C pins already have pull ups, I’ve not bridged the gap enabling the breakout pull-up. I’ve set both I2C solder ‘bridges’ to 0.
I attached the 10Ω SMD resistor “heating element”, gluing it to the top of the IMU with Arctic Silver thermal epoxy adhesive*; I couldn’t find a UK vendor so bought it from the US via e-bay. Once the epoxy has set (I give it a good couple of hours to be sure), I soldered on a couple of IDT pins to the resistor. Finally, I surround the IMU with a wrapping of blue-tak pure to provide thermal insulation.
Now I can attach the DroTek 10DOF IMU itself to the PCB IDT pins already soldered onto the board. And that’s it:
The next article will cover getting the A+ and beret firmly attached to each other and to a base which are all aligned / parallel to each other.
*This is the stuff used by psychotic overclockers on gaming machines along with water-based CPU cooling etc etc.