Tobias Kaiser
A Computer Engineer's Projects and Ideas

Servo tester

Picture

PCB

PCB

Demo video

Coming soon

Timeline

For me, this project was my learning project to get started with KiCad. Even though I learned the Eagle CAD program and used it for my first board, I was unhappy with their licensing and pricing ideas, since I have the intention to make large PCBs in the future. Even though my first impression of KiCad (when you first open it) was not that great, I worked through the KiCad beginner tutorial and found KiCad easy to use and the user interface design very clever.

So this PCB is just the result of my first test project with KiCad. From my experience through this project I decided to use KiCad for my future projects. I see no reasons to use anything else at the moment.

Description

This is essentially a little battery powered device that generates a 5 V PWM signal, which can be used to contorl the setting of a servo motor or a constant speed drive?! Motor drivers and servo motors with integrated drivers, which are often found in RC models, expect such signals. The duty cycle setting is used to set the position of the servo motor or the speed of the motor. The duty cycle setting can be controlled through the

Known issues

  • The MCU had no ADC, contrary to what I believed. Even though I did not order the PCB yet when I found that out..
  • Two parts of the ground plane were disconnected, and a trace that was supposed to provide the connection was unintentionally left unconnected to the ground planes.
  • A resistor at the buck converter was connected to GND instead of VCC?
  • The seven segment displays are multiplexed in a common cathode configuration. There I made the textbook mistake of placing the resistors on the common terminal. As a solution the LEDs are driven in a 28-way multiplex instead of just 4-way multiplex. In order to maximize the brightness, I replaced the resitors with smaller values.
  • After the replacement with the smaller resistors, it was not possible to use the in-system programmer anymore. This was solved by disconnecting the trace for driving the dot segment LEDs, which I did not intent to use anyways.

Source