Zachary Blair's Website

• Schematic
• Microcontroller source code
• CUPL source for the GAL16V8
• Download video of demo

The robotic turret was a project I devised to experiment with five technologies I was interested in: 

• stepper motors (unipolar)
• the Atmel Attiny2313 microcontroller
• MCU output compare features
• GAL-based programmable logic
• and RS232 communication using a PC's serial port.

Essentially, I wanted to be able to control a little robotic arm / turret using a PC with a serial port. I thought this was a worthwhile project because I could later adapt it to aim a webcam, Nerf toy gun, or maybe even a felt pen so it could draw pictures.

One stepper motor rotated the base of the turret, while the other adjusted the turret's pitch. I designed a stepper motor controller IC using CUPL (Univeral Compiler for Programmable Logic) and a GAL16V8 chip. This enabled an Atmel Attiny2313 MCU to control the two stepper motors using only three of its pins (one each for step, motor, and dir signals).

The Attiny2313 served as the "hub" that connected all the other components together by receiving commands from the PC via a MAX232N IC, performing basic calculations regarding the turret's position and velocity, and then sending signals to the GAL16V8-based stepper-motor controller to drive the two stepper motors. In order to supply the voltages and currents necessary to drive each stepper motor, I used a Toshiba ULN2803A Darlington transistor array.

By clicking on the image to the right, you can view a video of the turret working. I wrote a program for my PC that would send the appropriate commands to the turret for it to follow a target on my computer screen. The result is quite entertaining.

By clicking on the image below you can view a schematic I quickly put together of the circuit. It likely contains errors, but should at least provide a general idea of how the circuit is constructed.