The code that I’m currently using is from Julie VK3FOWL and Joe VK3YSP. They seem to be heavily involved in the School Amateur Radio Club Network (SARCNET), which has comprehensive build instruction for the Mini Satellite-Antenna Rotator (in several versions). As is generally the case, I have deviated a little from their plans by using a Arduino Uno rather that a Arduino Pro Micro Board.
The most expensive single component so far is the case (at $34). The software has several menu items that allow you to test and calibrate the unit. And you can also manually control it by entering the AZ and EL (in degrees with a space between them). You do this with a RS232 (TTL levels) interface to a PC running a terminal program like Putty or the equivalent on a Raspberry Pi.
One issue was that the USB to TTL fob that I was using, did not drive the Uno RX pin to ground (but only down to about 2.5v). The RX and TX pins on the Uno are also used for the USB connector and so the RX input requires a little additional encouragement to pull it to Ground. (Note: this would not have been a problem if I had used the Arduino Pro Micro Board.) I added a couple of FETs (2N7000) with resistors (10k) to get the +5 to 0 volts swing required.
Once the mechanical work is completed, I’ll use a Pi running Gpredict ver. 1.4 (already tested) to track the satellites and send the AZ and EL data to the rotator. Gpredict can also control the radio (taking into account the doppler shift). At least that what I’m aiming for! So watch this space!
Note: - In the video, I firstly entered '270 0' before entering '270 45'. You can see this as the rotator does not start to elevate until the second entry is made.
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