Building The FODTrack Tracking Interface
This is a re-work of an article I had published in November 2001 “73 Magazine”. Any design using a printer parallel port is a bit dated now, but it still might be an interesting read for some folks.
Here is a low-cost solution to fulfil your automated satellite tracking needs. Manfred Mornhinweg, xq2fod has made this free for noncommercial use. He says “If you want to reward me somehow, write a piece of useful software and put it in the public domain!” I have built several of the FODTrack interfaces for less than $35.00 each using all new parts. Here is what I have found.
The FODTrack controller connects to the parallel port (the printer port) on your computer, and plugs directly into the back of the controller for the Yaesu G-5400/5500/5600 rotators. If you are using another rotator or combination of rotators you will need to do some modifications. All of my testing has been done with a Yaesu G-5400B rotator package.
I started by downloading the entire FODTrack package from the PC Software section of the AMSAT web site. As of writing the current version is 2.6. The package contains some pretty good documentation as well as the schematic and art work for the circuit board. FODTrack is much more than just a tracking interface, but I am limiting my discussion to that portion.
Let’s move to the computer end. The parallel port, your new computer may not have one! If it doesn’t you can buy PCI or ISA cards that will add parallel port(s) to your system. You may want to consider pulling that old 486 out of the closet and using it exclusively for tracking. If you only have one parallel port maybe it is time to buy a new USB printer and free the parallel port up for the FODTrack. Maybe you just need a parallel port switch and can select between the FODTrack and the printer. Any way you need a parallel port to make this work! Personal experience recommends that you do not switch from printer to FODTrack or FODTrack to printer with the computer on. Let’s just say this is why I know the PCI parallel port cards work!
Figure #1 is the schematic. It is not that complex of a circuit, and should not be too difficult to wire point to point. I chose to etch my own board from the included artwork file. I just printed it out on a laser printer (actually printed it twice on the same sheet of paper for a double coating of toner), and ironed it onto some circuit board material. If you do this be sure to touch up any light or missing spots with a permanent marker. I did the same thing for the parts overlay and ironed it on after I etched the board. Radio Shack’s circuit board experimenters kit has enough materials to do three of these boards. I have since learned the boards are available from FAR Circuits.( http://www.cl.ais.net/farcir/ )
Figure #1 Schematic Diagram
Unlike many projects, this one does not require any unobtainium. All of the parts except the circuit board are available from Digi-Key (http://www.digikey.com/ ). My parts list follows:
Qty. Digi-Key Pt# Description
1 (5 pack) 10KQBK-ND 10 K Ohm Resistors
2 (5 pack) 15KQBK-ND 15 K Ohm Resistors
2 (5 pack) 20KQBK-ND 20 K Ohm Resistors
1 (5 pack) 39KQBK-ND 39 K Ohm Resistors
1 (5 pack) 56KQBK-ND 56 K Ohm Resistors
1 (5 pack) 100KQBK-ND 100 K Ohm Resistors
1 (5 pack) 1.0MQBK-ND 1 M Ohm Resistors
3 P4201-ND .1 microfarad Ceramic Cap (100 nanofarad)
2 P5148-ND 10 Microfarad Electrolytic Cap
1 LM340T-5.0-ND LM7805 Voltage Regulator
2 296-1391-5-ND LM324 OpAmp
1 296-1395-5-ND LM358 OpAmp
1 296-1871-5-ND 7528 Analog to Digital Converter
4 1N4148MSCT-ND 1N4148 Diodes
4 2N3904-ND 2N3904 Transistors
1 SW102-ND Switch
1 AE7220-ND 20 Pin IC Socket
1 AE7208-ND 8 Pin IC Socket
2 AE7214-ND 14 Pin IC Socket
1 AE1112-ND Parallel Cable (Get the length you need)
1 275-1005-ND 8 Pin Male DIN connector (plug in to rotor box )
1 HM104-ND Box
1 Circuit Board (not from Digi-Key)
Additional wire, tools, etc.
Figure #2 shows my completed circuit board. Use standard building techniques. Solder in the sockets, but don’t put the chips in the sockets until you are ready to go. I have a couple of construction notes to share. I must confess I raided my junk box for a couple of the parts shown in the picture. If you use the parts list above you won’t have any resistors wired in series for equivalent values. I could not find the BC546 transistors shown in the schematic. It doesn’t do anything other than switch so I substituted a good old 2N3904, just about any NPN transistor would do. The 2N3904 has worked well. The legs on the 2N3904 are in a different order than the BC546. They wind up going in backwards from what the parts overlay shows. Just make sure your base, collector and emitter connections are the same as in the schematic and you will be fine. It is cheaper and easier to buy a manufactured parallel cable (make sure it is long enough) and cut it and connect it to the circuit board. Building a cable from the ground up is more heartache than it is worth. Just use your ohmmeter to determine which wire connects to which pin. For added show I placed an L.E.D. in series with the output (collector) of the up, down, left and right transistors. This way I get an indication when the controller is moving the antennas.
Figure #2 Completed board
Figure #3 shows my completed controller. My up, down, left, right L.E.D.s are on the left-hand side. You may have to do a tiny bit of filing or trimming on the circuit board to have it fit in the enclosure I have chosen. Be sure not to damage the circuit board traces if you do this. Since the enclosure is black I printed white text on a black background from the paint program onto the labels. I think it looks nice!
Figure #3 Completed Unit
Follow the included instructions for calibration and setup and you should be set! There is a driver available to use the FODTrack interface with WISP. There maybe other drivers as well. I use the FODTrack program that comes with the package. It is easy to use and free! I also use FODTrack for Doppler compensation, but that is another story. Hope to hear you on the birds.
73, Joe kk0sd
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