W9KE Satellite Tracker - iPoint

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The iPoint project is a simple portable system for visually identifying the location of amateur radio satellites. It connects to your computer with a USB or Serial Port connection. A satellite tracking program such as SatPC32 sends tracking information to the iPoint which then controlls the azimuth and elevation motors moving the pointer. This is not a kit of parts project and I am not trying to sell anything. It is a description of what I did and you may pick up an idea or two that can be used in building your own projects.

Here is a youtube video showing the tracker in action http://www.youtube.com/watch?v=gnc4-XcEXEQ

The tracker uses a stepper to control the azimuth position. A second stepper motor is used to control the elevation position. Most stepper motors have limited radial and axial torque limits. This means that the azimuth motor should not bear the entire weight of the elevation motor assembly. In this design a simple chain drive is used to isolate the load of the elevation assembly from the azimuth rotor. Nylatron #25 chain was used. Nylatron chain is ideal for this application. It is clean as no lubrication is required. No master links are required so the length of the chain can be adjusted without any special tools. Nylatron chains are often used in robot projects. A web search for robot parts will reveal many sources of parts for this type of project.

A 1/4 inch shaft is used to support the elevation assembly. It is supported on both ends by bronze bushings held in place by two shaft locks. The shaft, bronze bushings and shaft locks were all obtained from the local Ace hardware store.

The elevation motor is attached to a bracket which is attached to a piece of aluminum that is simply connected to the shaft and held in place with a set screw.

Almost any stepper motor can be used. The motor controllers described in the motor control section are all for uni-polar stepper motors. Bi-Polar stepper motors would require a different type of motor controller.