30 second video: [video link]

Hackaday site: [click here]

Photo Galleries:  

[Rotor Gallery v0.10] -- Original build

[Rotor Gallery v0.20] -- Home-made circuit board

[Rotor Gallery v1.01] -- Thank you PCBWay.com!!!

The basic idea is for the Raspberry Pi to control the movement of an antenna rotor. This is accomplished using a 24v transformer, some relays, an op-amp and an a2d chip. A touchscreen is also attached to the Raspberry Pi so that the user can see the current aspect of the antenna and also input the desired direction he/she wishes the antenna to be moved to.

The system was designed around, and tested using a "Tail Twister" Model T2X - Rotator. A link to the owners manual is in the links section. My father, Dr. Bill Ryan also helped with the initial concept and design. 

Some of the basic components include standard relays, an A2D converter, and an op-amp.  The basic idea is that the op-amp will levelize the voltage coming in from the rotor's aspect indicator, and then the output of the op-amp will be fed into the A2D converter where the Raspberry Pi will read it and display on the screen the position of the antenna.  

Above is an example of a 500 Ω aspect indicator and also a scope image of what the voltage looks like, both directly coming off of the aspect indicator and after it is fed through the op-amp. When the motor is running there is a lot of 60hz interference, which is being captured on the yellow channel.  The voltage is fed through an op-amp which filters out the interference and leaves you with a steady voltage, as seen on the blue channel. 

The user can then input the degrees he wishes to move the antenna to, or using the touchscreen, he can press one of the preset buttons to move to a cardinal position.  VNC can also be used to control the system remotely. 

Using a set of relays, the Raspberry Pi can turn the rotor's brake on and off, and then activate the motor in the proper direction in order to move the antenna to the desired position.

Parts list: [click here]

Also, a huge thank you to Elliot Williams for his article on low pass filters which helped me greatly understand how they work and which one I needed to use in this project.

Low Pass Filter: [click here]