I just returned from the UAV Day @ The Fleet Center here in San Diego. Quite a few folks swung by the San Diego DUG table and asked about the antenna tracker I built. Joe Aletky from 3d Robotics asked me to share the build of material for the antenna tracker. There's the Antenna Tracker wiki but I wanted something a bit heavy duty for the field!
The parts list is mostly sourced from ServoCity and cost me about $200 to build at the time. From my understanding the price on the servos has gone up a bit.
You will need:
2 - Aluminum Channels, one for the antenna rail and one to hold the servo where you bolt down to the tripod. I'm running a 15" bracket and a 4-1/2" bracket.
2 - RobotZone channel mount gearbox, I went with 360 degree CLOSED LOOP servos. The ratio I used was 3.8:1.
2 - Servos. I went with HS-5485HB servos. If you're not good with a soldering iron, let ServoCity do the servos for you.
From Pololu you'll need:
The rest I'll share in pictures since they describe how I did it better than I can. I will STRESS the same thing that the wiki states. Keep your tracker clean and the wires out of the way. The gears have no mercy when it comes to chomping wires and fingers!
Back side of the antenna rail. I'm running a 900mhz patch and the BOSCAM 5.8 receiver with TrueRC crosshair antenna.
The video RX attaching to the Crosshair antenna. The bracket I took off of another antenna.
3dRobotics 'Ground' module. Soon to be swapped out with a RDF900! Hyperlink is now known as L-Com.
Here you can see the Pololu servo controller, the Channel C Bracket, the 4-1/2 channel and one of the monster servos. Again keep your wires clear! The servo will eat them! I drilled a hole through the tripod head (It's a cheap one) and bolted the channel down to the tripod head..
Up close of the Servos for Pan and Tilt. Here you can see the 90 degree hub mount bracket.
I use a regular BEC to power the servos from a 12v battery. Usually I'll draw this power from my lead acid ground station battery. I have two USB cables. One from the Telemetry and the other from the servo controller that plug into a USB hub. Those then plug into my laptop and tie into Mission Planner. From there everything is controlled via Mission Planner and the telemetry coming down from the plane.
Comments
Some stop motion video from UAV @ Fleet. You can see the antenna moving around and people stopping by the table. 3dRobotics is the second table to the right of the table the antenna tracker is on..
https://www.youtube.com/watch?v=Uvvox0hzQv8
http://item.taobao.com/item.htm?spm=a1z10.1.w4004-1135699374.2.c5jy...
I made something quite similar, I even used the Servo City gearbox on the pan axis. The problems I had were that, well, the gears are very fragile. I used the plastic gearing, and knocked it over in my shop, when it fell it stripped the gears off the big gear. So I started changing that over to a belt drive system. The belt should be more robust and reliable.
On the pitch axis, I use a rod coming out both sides, similar to what you did, but I mounted the antennas so that the rod goes through the middle of them. Hard to explain... the axis is aligned with the CG of the antennas, so that they don't load the pitch axis servo when tilting.
Can you just move your pitch antenna down so that it's in the middle of the bar? That would help.
I never quite finished mine, got caught up in other projects. No point having an antenna tracker when you don't have anything flying!
Rob - It actually does pretty well unless you overload it. I tried putting a -22dbi grid antenna on for giggles and it couldn't handle the load. I tried a few different configurations before coming to this setup with the small load. Including a setup that looked like a small antenna rotisserie.. I found if I put to much load on the pan servo it'll twitch trying to get back to center. I'm always open to suggestions!
Martin - So far it hasn't broken any leads. I want to try to move everything but USB and one Video out up onto the tracker. I'm tempted to draw up a PCB that funnels those connections into a Cat5 cable. If I munch a cable or a lead breaks I can simply crimp a new Cat5e cable.
Not a bad setup. How does the pitch servo deal with the fact that the antenna mass is not in-line with the pitch axis? If it tilts up, the antenna mass will be trying to pull the pitch up even more as the antennas "fall back". Also, wind load would do the same, try to push back on the pitch.
Looks nice, but how's the wiring going to take that continuous winding and unwinding?
"Obtain from Module" is if you have a garmin gps attached to the tracker. currently it only supports usb garmin devices, and was a contrib from Will Bryan
I recon most of these parts can be 3D printed to reduce the cost.
Usually the first thing I do is power up everything and get a solid GPS lock on the APM. After that I'll set my plane in front of the antenna tracker and zoom in REALLY tightly in Mission Planner under the Flight Planner window. I'll then right click and say Tracker Home -> Set here.
Then I'll drag the antenna tracker pin right on top of home and drop it. That should get me pretty close to where my antenna tracker is placed.
After that I'll flip over to the Initial Setup tab under Antenna Tracker and pull down the COM port for the Pololu servo controller and go with 9600 baud. When that's set I hit connect. At that point the tracker should go into motion.
You should be able to move the plane a few meters in front of the antenna tracker should move with it. If you need to reverse the direction it's pretty self explanatory. The sliders allow you to trim where the antenna needs to be facing. When you start up the system will think you're facing north. If you're facing East or West you have to aim accordingly. Nathaniel Caner documented some of this stuff starting back in December when he started venturing into antenna tracking. He was some inspiration into building my antenna tracker so my hats off to him and Michael Oborne.
You can use Pololu Maestro Control Center to figure out your PWM settings and how far your servos an travel. Usually the PWM setting is (Large Number - Small Number) = PWM. In my case 2000 - 960 = 1040 for pan and 1904 - 1456 = 448 for my tilt. That'll give me a 45 degree angle for tilt and 360 for pan. You can get these numbers on the status tab in Maestro CC. Be careful NOT to go beyond the recommended travel! On the Servo City gear boxes you'll hear the POT start to click and the servo will just spin. At that point you get to play the servo centering game.
One thing to note with the Pololu board is you may have to set it into USB Dual Port under Serial Settings. This allows you to connect to the COM port.
If anyone wants to shed some light on the new "Obtain from Module" setting in Mission planner I'd love to know the story! I've tried plugging a GPS in to see if I could get it that way or from a live feeding APM.
Hi, nice setup. How do you configure mission planner to control the antenna tracker? I know there is a menu called Antenna Tracker, but I only see two interfaces, maestro and ardu tracker.
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