This week, I’ve finished up integrating the vertical aiming and radial aiming system, wired up all the circuitry, and wrote preliminary modules for controlling both axes. The servo motor only requires 5V of power, so it can be directly powered by the Pi. I’ve wrote a simple script that can translate angle input to PWM signals so change the servo’s position. I initially tried working with RPi.GPIO library, but observed some jitter. Turns out this library generates PWM signals through software but doesn’t utilize the PWM hardware in Pi, so I experimented with pigpio library which does interface with the native PWM hardware – this proved to be very stable.
Utilizing the stepper motor was tricky as well – the block connector on the stepper motor expansion board was faulty (the screw was too tight), so I’ve de-soldered the original block connector with a new one. I’ve observed that the circuitry was drawing too much current (2A) when I was playing around with it even when the motor was at rest, but that was due to not calling the cleanup code from the software side. After some experimentation, I was able to reliably control the direction and movement of the stepper. Here is a video of both system working together. I am controlling the servo and stepper by ssh-ing into the pi.
I’ve also printed out a new spinning top and servo base that can be mechanically connected together so the whole system connects seamlessly. Here are some pictures of the aiming system and the circuitry below:
I am back on track with the schedule. I am on pace to finishing up the aiming system next week.
There are some more fine tuning that has to be done – both the servo and stepper movements are too abrupt and needs some slowing down from the software side. This is especially problematic with the stepper since I observed that it is very powerful and can move the entire base (the current version’s base is not mechanically stable). By next week, I aim to fine tune the control so it is stable, and start CADing the entire robot that can encapsulate circuitry and a pole for the camera as well. I will also implement a simple server that can take in HTTP request from the frontend and communicate with the motor control modules.
