AA1YN on Moonbounce

Project Moon Tracker

The goal is to have 4 16ele K1FO crossed yagis and be able to switch polarity for either/both transmit and receive. I will be putting some photos of my construction project (have the H frame, the Azimuth and Elevation drives, tower, and thrust bearings complete. I have the material for the yagis, and I have to design/program the tracking computer. The mounting of the H-frame is such that it can be removed and a dish put up in place of it.

Here are some photos of the components going into the moonbounce setup

The H-Frame cross boom was welded up from some scrap aluminum I had kicking around. So far it seems to be fairly sturdy but time will tell.

A photo of the mid section of the H-Frame which will mount onto the mast. The pipe is 1" X 0.125 stainless. The bearing mounts are aluminum with Delrin bearing material.

A detail photo of the end of the cross boom. I decided to have some flexibility for the adjustment of the seperation between the antennas so I could optimize. I will probably start off with horizontal only polarization and then switch to cross polarization in the future.

Here is the azimuth rotor under construction. The motor drive is a 36v DC motor removed from a TVRO dish. It has an output of 60 rpm with switch feedback giving 8 pulses per revolution. You can not stop the output of the DC motor by hand no mater how hard you try so I think there should be enough power to turn the array. With 8 pulses per revolution of the DC motor, and a total of 300:1 speed reduction, I get 2400 pulses for a full 360 degree rotation of the array. This gives me 1 pulse per 0.15 degrees which should be adequate resolution. The speed reducer is from an old conveyor belt drive providing 100 to 1 reduction. You are looking at the bottom of the rotor as the output will be facing down. The output sprocket is a double 1/2" pitch chain with some 7000 lbs working strength. The chain drive will provide an additional 3 to 1 reduction. I've been warned to make sure the antenna array never gets stuck as it may influence the Earths rotation :-)

A photo of the rotor being tested with the moontracker interface.

A photo of the mast thrust bearings. They were constructed from solid 4" aluminum rod stock. The insert bearing material is Delrin.

A photo of the thrust bearing exploded to show the construction detail.

The front panel photo of the moontracker interface. This interface takes the serial output from the Nova tracking program via the Easycomm protocol, keeps track of where the antenna is pointed, and provides the DC drive to both the azimuth rotor and the elevation linear actuator. This interface was based on the Houston Satellite Systems Tracker IV. Unfortunately the original front paned did not lend itself to the new design.

An inside photo of the of the moontracker interface. It is based on the MicroChip PIC18lf458 device. The board is a Vector breadboard I scrapped from the Intel 8008 PC I built a long time ago. I used both regular descrete and SMT devices along with soldered wire and wire-wrap connections during construction.

A photo of the rear panel of the moontracker interface.

The schematic of the moontracker interface. - This jpg file is over 1mb in size! As you can see, there isn't much to it. Most all work is done in the software. At present, I'm using 5700 bytes of program space out of 16K available so there is plenty of room to expand. Since it is dependent on a PC already, most all functionality will require the use of a PC. There is a prevision for full manual operation as can be seen on the front panel image above. I am building in a number of commands accessed via Hyper Terminal so it can be switched from digital feedback mode to analog, all calibration functions are entered this way, park and home commands, plus what ever else I think of.
The two H switches are made up of International Rectifier's Power FETs capable of 75 amps of current at up to 55 volts. The main reason for choosing these are the low on resistance and the reverse emf disapation. You will notice there is very little in the way of a heat sink (only the azimuth is installed in the photo) as there is no power disipated in the on state. The only time they disipate any power is turning off where the devices sink the counter emf. Even then, they only get slightly warm to the touch.
Please note, this is a preliminary diagram and a couple of changes have already been made.

I am designing the software which executes on the PIC Micro-controller from scratch. Since the controller has both a manual and an automatic mode, I needed some way of communicating with the program. I chose to use the Hyper Terminal which comes with most Windows Op Systems. Any terminal emulator will do. The terminal window can use the same comm port as the Nova program so it is easy to debug without trying to run Nova. Since there are a number of commands I could use, I created a command parser in the software and display a help screen. A simple "?" followed by a Return displays the help screen. You can see some of the other commands available.
A command allows you to enter Az and El in the format
AZnnn.n ELnnn.n
C command allows you to enter the current bearing and elevation just incase something went wrong (Great use in debugging).
E command allows you to toggle the echo mode so you can see what you are typing. The tracking programs which use the EasyComm protocol, do not accept data into the serial port thus the port overflows on input data causing headaches.
H command allows you to move the antenna to the home position. The azimuth and elevation data is set to the home bearings when the home switches are encountered. These home switches should be mechanically set to a known bearing.
P command allows you to move to a park position which is probably different from the home position.
Various S commands allow you to enter data for parameters used by the software. Some of the parameters which are used in calculation, are stored in EEProm and retrieved upon boot up.
Speaking of boot up (power on), when the controller detects it has lost power, it stores all volitle data in EEProm prior to loosing power. This data is then restored when power is turned back on. This way, we don't loose the position of the antenna if we loose power - been there, done that!

A few of the program parameters are stored in EEPROM which allow me to tune the software to the hardware. Being able to set these parameters and being able to display them is important to me. Here is a screenshot of the status display.

| AA1YN Home | VHF Home | WSJT Home |


		The H-Frame cross boom was welded up from some scrap aluminum I had kicking around. So far it seems to be fairly sturdy but time will tell.

		A photo of the mid section of the H-Frame which will mount onto the mast. The pipe is 1" X 0.125 stainless. The bearing mounts are aluminum with Delrin bearing material.

		A detail photo of the end of the cross boom. I decided to have some flexibility for the adjustment of the seperation between the antennas so I could optimize. I will probably start off with horizontal only polarization and then switch to cross polarization in the future.

		Here is the azimuth rotor under construction. The motor drive is a 36v DC motor removed from a TVRO dish. It has an output of 60 rpm with switch feedback giving 8 pulses per revolution. You can not stop the output of the DC motor by hand no mater how hard you try so I think there should be enough power to turn the array. With 8 pulses per revolution of the DC motor, and a total of 300:1 speed reduction, I get 2400 pulses for a full 360 degree rotation of the array. This gives me 1 pulse per 0.15 degrees which should be adequate resolution. The speed reducer is from an old conveyor belt drive providing 100 to 1 reduction. You are looking at the bottom of the rotor as the output will be facing down. The output sprocket is a double 1/2" pitch chain with some 7000 lbs working strength. The chain drive will provide an additional 3 to 1 reduction. I've been warned to make sure the antenna array never gets stuck as it may influence the Earths rotation :-)

		A photo of the rotor being tested with the moontracker interface.

		A photo of the mast thrust bearings. They were constructed from solid 4" aluminum rod stock. The insert bearing material is Delrin.

		A photo of the thrust bearing exploded to show the construction detail.

		The front panel photo of the moontracker interface. This interface takes the serial output from the Nova tracking program via the Easycomm protocol, keeps track of where the antenna is pointed, and provides the DC drive to both the azimuth rotor and the elevation linear actuator. This interface was based on the Houston Satellite Systems Tracker IV. Unfortunately the original front paned did not lend itself to the new design.

		An inside photo of the of the moontracker interface. It is based on the MicroChip PIC18lf458 device. The board is a Vector breadboard I scrapped from the Intel 8008 PC I built a long time ago. I used both regular descrete and SMT devices along with soldered wire and wire-wrap connections during construction.

		A photo of the rear panel of the moontracker interface.

		The schematic of the moontracker interface. - This jpg file is over 1mb in size! As you can see, there isn't much to it. Most all work is done in the software. At present, I'm using 5700 bytes of program space out of 16K available so there is plenty of room to expand. Since it is dependent on a PC already, most all functionality will require the use of a PC. There is a prevision for full manual operation as can be seen on the front panel image above. I am building in a number of commands accessed via Hyper Terminal so it can be switched from digital feedback mode to analog, all calibration functions are entered this way, park and home commands, plus what ever else I think of. The two H switches are made up of International Rectifier's Power FETs capable of 75 amps of current at up to 55 volts. The main reason for choosing these are the low on resistance and the reverse emf disapation. You will notice there is very little in the way of a heat sink (only the azimuth is installed in the photo) as there is no power disipated in the on state. The only time they disipate any power is turning off where the devices sink the counter emf. Even then, they only get slightly warm to the touch. Please note, this is a preliminary diagram and a couple of changes have already been made.

		I am designing the software which executes on the PIC Micro-controller from scratch. Since the controller has both a manual and an automatic mode, I needed some way of communicating with the program. I chose to use the Hyper Terminal which comes with most Windows Op Systems. Any terminal emulator will do. The terminal window can use the same comm port as the Nova program so it is easy to debug without trying to run Nova. Since there are a number of commands I could use, I created a command parser in the software and display a help screen. A simple "?" followed by a Return displays the help screen. You can see some of the other commands available. A command allows you to enter Az and El in the format AZnnn.n ELnnn.n C command allows you to enter the current bearing and elevation just incase something went wrong (Great use in debugging). E command allows you to toggle the echo mode so you can see what you are typing. The tracking programs which use the EasyComm protocol, do not accept data into the serial port thus the port overflows on input data causing headaches. H command allows you to move the antenna to the home position. The azimuth and elevation data is set to the home bearings when the home switches are encountered. These home switches should be mechanically set to a known bearing. P command allows you to move to a park position which is probably different from the home position. Various S commands allow you to enter data for parameters used by the software. Some of the parameters which are used in calculation, are stored in EEProm and retrieved upon boot up. Speaking of boot up (power on), when the controller detects it has lost power, it stores all volitle data in EEProm prior to loosing power. This data is then restored when power is turned back on. This way, we don't loose the position of the antenna if we loose power - been there, done that!

		A few of the program parameters are stored in EEPROM which allow me to tune the software to the hardware. Being able to set these parameters and being able to display them is important to me. Here is a screenshot of the status display.