Servo Controller with USB Interface

Overview

The USB-Servo project describes a device used to control a servo through USB.

Explanation

Commonly used in remote controlled cars and planes is a motorized device known as servo which are connected with 3-wire cables. The power uses a red and a black one while a yellow one for the signal. The 5V from the USB port is suitable to power the servo since it requires 4.8V to 6V. the servo can be connected directly to the controller and the signal does not take much current. A signal of about 50Hz is being obtained with one pulse every 20ms. The length of the pulse tells the servo the angle to adjust since the angle of the servo is controller with pulse width modulation (PWM).

In the design, there are 3 parts which include the firmware for an ATmega8 microcontroller, a command line client that can be run under Linux, and the circuits needed to build the device. The circuit contains only a few standard components and there is no special USB chip involved. The device will be connected to the USB port and the servo will move to the 0-position if not yet ready.