Hi all, I have started a new project with the intention of making it open source. It is an all in one reciever board for high end remote control planes.
The way that rc planes are currently made is by independent off the shelf modules with secret black magic components. These components (speed controllers, recievers, video transmitters, battery circuitry) are all expensive , and made from a handful of independent companies.
My goal:
- low cost
- simple
- video transmitter (for first person flying)
- 6 channel rc receiver (possibly just use a hobbyking one as a daughter board for simplicity and compatibility)
- current monitor
- low battery voltage protection
- brushless electronic speed control
-fiberglass board will double as a wing spar to save on weight
Pretty cool huh?
The reason that I am posting this is that I have reached a hiccup in my design. The brushless speedcontroller is complicated as hell. I have read research papers (
http://scholar.lib.vt.edu/theses/available/etd-09152003-171904/unrestricted/T.pdf) and I have taken apart a speed controller of my own. The thing that puzzles me is the implementation of inductive spiking as a feedback mechanism, and speed control.
To start discussion off, I have taken a magnified picture of my speed controller. Ignore the left half, as all it is is power regulation, filtering, and input buffer. In the middle of the board, there is an atmega 8 MCU and what I suspect is an ADC. The back has a heatsink that I cannot remove, but I suspect it to have 3 n channel fets and 3 p channel fets. The right sight of the top has 15 resistors 3 transistors, and what looks like an rc tank ciruit. The top three are resistors in pull down configuration. The next 6 below them look like resistor dividers. Presumably they are to attenuate the inductive spikes so that they wouldn't blow the ass out of the transistors. The next 3 resistors look like base drive resistors for the next 3 transistors. My guess is that the transistors are another step of isolation between the adc and the motor. They could also be used in a multiplexer system, i have no idea. The rc time constant could be for sample rate or something. I feel really out of my league here
Thank you for reading through my project. Any help is appreciated. Thank you!