This repository contains the firmware and the CAD files used to construct a basic camera inspection rover.
The rover is build based on a modified 1:18 scale RC car. The model used here is a PulseLabZ HS18321 but this should work with pretty much any RC car.
The car is modified to work with a Futaba R2004GF 2.4GHz 4 channel receiver.
2 Channels of the receiver control the servos for the X and Y axis of the camera gimbal. One channel controls the motor speed and the remaining channel controls the servo for the steering.
The 2 servos in the gimbal are Hobby King HK-933MG.
For the motor speed controller I opted for the Hobbywing Quicrun 1060 60A 2S-3S ESC (brushed).
The gimbal is a custom design meant for a GoPro 7. It uses 2 standard RC servos.
The cad files for the gimbal are in the cad/gimbal directory.
The gimbal also has a light bar attached. The light bar is a simple custom etched PCB with 0805 LEDs (white) and 0805 resistors (220R).
The design files for the light bar are in the pcb/light-bar directory.
The STL files for the gimbal are also available on Thingiverse.
One of the challenges was that the RC car was meant to go fast. For the intended use case a slow speed was desired though. Simply being careful with the control sticks wasn't really working as the slightest input resulted in significant acceleration.
I used an Arduino Pro Mini to sample the PWM signal from the RC receiver and then mapped it into a new PWM signal that would drive the motor at a reduced speed. This also accounts for the fact that the car normally drives faster when going forward than going backward when given the same input. With the custom firmware the forward and reverse speed is the same.
The firmware for the motor control is in the src/firmware directory.
Another issue was that the servo to control the steering was a 5 wire servo and not a conventional 3 wire servo. To make the steering servo compatible with the RC receiver I transplanted the electronics from a standard 3 wire servo into the 5 wire servo.
The process for that is quite straight forward. There is a good video available here.
The rover uses 2 enclosures. One for the battery and one for the rest of the electronics. The reason to separate this is to prevent having to access the electronics compartment when switching out the battery.
The cad files for the enclosures are in the cad/box directory.
