Autonomous Satellite Tracker

This page refers to my Autonomous Satellite Tracker article in the March/April 2016 QEX. All updates will be posted here.

Supporting Material: Published article Manuscript, updated after publication Block diagram Screen shot of web interface Arduino source code, Version 2016082822 Alternative to Print.cpp in core Arduino library

Images: Operating Prototype movie Controller close-up Tripod close-up Tilt servo close-ups: #1 #2 Pan servo close-ups: #1 #2

Notes: Version 2016061704 fixes a problem that prevented entering values in Firefox and Android. Version 2016073023 fixes a problem that prevented downloading elements from AMSAT or Celestrak in Firefox and Android. Version 2016082822 fixes a problem with refraction near the horizon. I've added a closeup photo of the way I connected the tracker to a tripod. I bought a small tripod and pulled the center post up through a channel then clamped to it. The tripod post is 5/8" diameter. ServoCity part numbers: 3x 585548, 1x 585443, 1x 545360 and 2x 585596. Notes from a builder, WA7DLG. Gregg, W7GRM, reports the HS-7950TH servo for the SPT400 platform is strong enough even for the Arrow antenna.

Update 2018 July 29: The Tracker is now available using the ESP8266 processor, the same one used in my HamClock. This eliminates the need for the Arduino, ethernet shield and the TP-Link. The wiring diagram and interior view are now just this:

The wiring for the Servo controller, 9 DOF Sensor and tilt and pan servos is the same as in my original design. Note the change from 5 to 3.3 V supply for which the Huzzah EN is grounded. If you use a 5 V supply then leave EN disconnected.

Update 2020 Jun 16: Changes:

• updated to 2020 World Magnetic Model
• fixed bug where very low sat pass could cause crazy pass drawing
• fixed bug where mag decl could remain as default after first GPS lock
• use simpler SoftwareSerial constructor for newer ESP8266 board support

The new sketch is here. Set up the Arduino IDE for the Adafruit ESP8266 Huzzah exactly the same as described in the first answer in the FAQ tab of my HamClock project. Use the IDE Library manager to also load the following libraries:

• Adafruit BNO055
• Adafruit PWM Servo
• TinyGPS

The Tracker functions exactly the same way as described in the original article except how it connects to the network:

• When the Huzzah powers up it will try to connect to the WiFi access point it last used and be at the same IP as before.
• If this fails, the Huzzah creates its own open WiFi Access Point called "SatTrack".
• Connect to this AP then surf to http://192.168.10.10.
• You should see a form where you can fill in the credentials for your WiFi and the network details you want assigned to the Tracker. The WiFi creds must use only the characters a-zA-Z0-9.
• Click Send, wait a few seconds, then turn off the Tracker.
• Connect back to your normal WiFi AP.
• Turn Tracker on, wait a few seconds, then you surf to the Tracker at the IP you specified in the form.

Servo City seems to have discontinued the gimbals I used. One builder reports he will try to use this one although I have not tried it myself. Without the extra 5:1 gearing it's not clear whether this can hold an antenna.

Thomas, DL2TW, twinterfeldt at web dot de, has made some code changes, such as a TFT status display and allowing more characters in the WiFi credentials. I've not tried his changnes but you can get his zip file here if you want to check them out.

Let me know what you think!

73, Elwood Downey , WBØOEW