Open RSSI Antenna Tracker

Are you in-to First Person Viewing? Got an interesting hack/mod? Let us know!
Post Reply
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Open RSSI Antenna Tracker

Post by Rob Thomson »

Well... Title pretty much says it all.

I have been building an rssi tracker for my FPV models.

A little video of the results of my diy can be seen in this video.

https://www.youtube.com/watch?v=aa654Xc ... ata_player

I will post a build log and arduino code to this thread soon.

Rob

Sent from my GT-I9300 using Tapatalk now Free
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!

User avatar
kaos
Posts: 3247
Joined: Wed Dec 28, 2011 1:15 am
Country: United States

Re: Open RSSI Antenna Tracker

Post by kaos »

that looks like child abuse to me. :P Just joking!

I see you have two helical and two circular ant on it. why not put helical for video as well?

This is interesting. Do you have a detailed plan/diagram?

How would this rssi/diversity compared to a GPS tracking system? I think Brent was talking about that a while ago. Don't know what happened to that project. He was looking for a mathematician.

Just received my 2W wifi booster today. This tracking ant thing is probably not too far from my 'working list'. ;)
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

There ate actually 4 antennas.

two five coil helix on the outside.
1 three turn helix up front
1 clover on top

The system aims to keep the front antenna pointed at the model. What it also then does is to use a video switcher to auto switch feed to the stronger antenna.

So if you you fly overhead... Then clover takes over :)

It tracks very well.

I will hopefully have a build guide up today.

Rob


Sent from my GT-I9300 using Tapatalk now Free
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

Ok.

Not going to go into heave detail here.

The system is very easy to build. The base platform ideas cam from this thread.

http://www.rcgroups.com/forums/showthre ... 08&page=22

At a basic level your parts list is:

1 center antenna
2 outer antennas
3 receivers
1 360 degree servo
1 slip ring
1 arduino (almost any should work)
1 lazy susan bearing
1 fpv video switcher

The system works by measuring the RSSI values from each antenna.

Getting an RSSI value from it is easily done using PIN six on the module.

Image

You can happily leave out the buffer circuit shown. I did originally have them, but scrapped it due to heat issues melting my insulation. All that is needed for my tracker is the lead from pin 6 on the rf module - but if you want the buffer. No issue. It will still work.

Each of these values is measured, then used to drive a servo left/right depending on which one is the strongest.

Have a read of the rcgroups thread, and check these videos

Thead:
http://www.rcgroups.com/forums/showthread.php?t=1337608


Video:
http://www.youtube.com/watch?v=V2W9wiUJuf4

They will give a good idea of the construction of this sort of tracker.

What I have done is to provide a 'digital' control board to replace the analog one they use.

This is much more flexible, and general more 'stable'.

Attached is the arduino code. Very simple to follow :lol:

Shout if any questions.

Rob
Attachments
tracker.zip
(2.13 KiB) Downloaded 1143 times
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
jhsa
Posts: 19480
Joined: Tue Dec 27, 2011 5:13 pm
Country: Germany

Re: Open RSSI Antenna Tracker

Post by jhsa »

Ha ha, that picture came from my friend Michael's website.. ;)

I saw him at the field with his equipment.. His tracker seems to be working well. He wasn't doing FPV there (because it is not allowed at the field), but just flying his twinStar LOS and we were watching the video.. the antenna tracked very well

João
My er9x/Ersky9x/eepskye Video Tutorials
https://www.youtube.com/playlist?list=PL5uJhoD7sAKidZmkhMpYpp_qcuIqJXhb9

Donate to Er9x/Ersky9x:
https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=YHX43JR3J7XGW

User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

Cool :)

He has done similar trackers the mine.

Sent from my GT-I9300 using Tapatalk now Free
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
kaos
Posts: 3247
Joined: Wed Dec 28, 2011 1:15 am
Country: United States

Re: Open RSSI Antenna Tracker

Post by kaos »

OK (you said shout ;) )
the 3 helical are for radio tx and use the circuit to track? I also see 2 circular ant. Those are for video? if so why two (any diversity circuit for these two?) Why not use helical for video as well, I read with a CL on vTx and a helical on vRx will get a longer range and better result. Where did I get this thing wrong?
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

Ah...

My setup is as follows

1 x 3 turn helix on left
1 x 5 turn helix in middle
1 x 3 turn helix on right
1 x clover on top (receive)
1 x clover on back (relay to goggles)

The one on the back is not really relevant to the circuit as just a 10mw tx module wired to the AV feed from the receiver.

The diversity circuit for the outer two is not strictly necessary. I simply added this because it gives me an extra degree of redundancy. What really matters for your actual feed is the center helix, and the clover.

Rob
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
kaos
Posts: 3247
Joined: Wed Dec 28, 2011 1:15 am
Country: United States

Re: Open RSSI Antenna Tracker

Post by kaos »

so this is only for video signal tracking? why not add the helical ant for radio as well?
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

I do.

I take the best signal from all the antenna, and use that one.

But it is not 100% necessary if just building a simple unit.

Sent from my GT-I9300 using Tapatalk
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
Kilrah
Posts: 11108
Joined: Sat Feb 18, 2012 6:56 pm
Country: Switzerland

Re: Open RSSI Antenna Tracker

Post by Kilrah »

I think he means adding a directional antenna for RC.
User avatar
kaos
Posts: 3247
Joined: Wed Dec 28, 2011 1:15 am
Country: United States

Re: Open RSSI Antenna Tracker

Post by kaos »

yep. ;)
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

I see.

You could do that.

Actually something I have considered - hence my threads a week or so back regarding repeating an frsky signal :)

Sent from my GT-I9300 using Tapatalk
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
kaos
Posts: 3247
Joined: Wed Dec 28, 2011 1:15 am
Country: United States

Re: Open RSSI Antenna Tracker

Post by kaos »

Cool. That is what I am thinking when building a tracker system. let us know your result. :)
I read only one time someone put a wireless relay station for RC, wonder what kind of 'lag' that would add to the control.

so in theory, you only need to add a helical for RC parallel with the center video helical, right?
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

I would personally use a patch. But no real difference.


I would also consider placing it on an arm - maybe half a meter away from the other antennas.


Rob

Sent from my GT-I9300 using Tapatalk
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
kaos
Posts: 3247
Joined: Wed Dec 28, 2011 1:15 am
Country: United States

Re: Open RSSI Antenna Tracker

Post by kaos »

I would like to see how you aim these two ant exactly parallel. ;) Isn't the patch ant only covers ~7 degree at distance?
wait, don't you need a 'tilt' tracking for RC? In the video, looks like you only have 'pan' tracking?
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

Tilt is useful.. But really no major issue for my needs.

The 4 turn helix has a 60 degree beam. That gives you quite allot of altitude. (And my antennas are pointed upward to prevent wastage of signal in the ground.

If the model flies overhead, out of the beam, the clover would automatically take over.

For the of, I would use this.

https://www.hobbyking.com/hobbyking/sto ... ules_.html

It is pretty much a wide beam, out the front of the antenna.

Rob

Sent from my GT-I9300 using Tapatalk
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
kaos
Posts: 3247
Joined: Wed Dec 28, 2011 1:15 am
Country: United States

Re: Open RSSI Antenna Tracker

Post by kaos »

hmm, forgot about that patch antenna, I have one too. with my 2W wifi booster and this tracking, that may get me to 15Km range. :mrgreen:
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

Correct. It will also avoid issues with polarisation - hence my reason for thinking a patch :)

Sent from my GT-I9300 using Tapatalk
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

My tracker has been through a few 'upheavals'.

Testing of the system found that whenever the servo triggered, I would get interference on my video.

By the look of it, it is power/ground loop related - but I need to test more to find the source.

In the mean time, I have stripped out the video switcher code, and the switching device.
- in this case I found that the power/ground issue was feeding through via this unit. I will need to investigate more to find a cure.

Additionally I have bypassed the video to goggle relay.
- My intention is to move this off the unit onto a separate small tripod. I found that the signal broadcasting so close to the receivers was just not working so well.

Overall, the code is lighter, and the changes to the wiring have mean less impact on the video signal. To that point - it is actually working perfectly!!

I went out today for a test flight, and successfully tracked the model to 600 meters. (further than I have ever flown). At that point, I decided that as I did not have a RTH system - it would be better to not risk it by flying too far away!

The attached code is my latest working version. It has a new calc in it that uses some maths and a constant to improve resolution, taking distance into account.

It works well!

Rob
Attachments
tracker.zip
(2.04 KiB) Downloaded 697 times
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
kaos
Posts: 3247
Joined: Wed Dec 28, 2011 1:15 am
Country: United States

Re: Open RSSI Antenna Tracker

Post by kaos »

glad to see you are progressing. This radio frequency/signal interference is really 'voodoo'. I am following this carefully.;)

when you look at my other thread for video Tx/rx, I had a heck of time to get a clear image. ;)
User avatar
kaos
Posts: 3247
Joined: Wed Dec 28, 2011 1:15 am
Country: United States

Re: Open RSSI Antenna Tracker

Post by kaos »

I was looking at this stepper motor. http://www.ebay.com/itm/221268196761?ss ... 1438.l2649
Why I never see people use this for tracking? any advantage /disadvantage of using a 360 servo and this. It is congtrolled idrectly by arduno. It seems to me this stepping motor has more resolution than a servo.
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

Steppers are great.

I actually have a plan to d a version with a stepper - just not gotten round to it yet.

Guess servos are just 'easy'.


Sent from my GT-I9300 using Tapatalk
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
kaos
Posts: 3247
Joined: Wed Dec 28, 2011 1:15 am
Country: United States

Re: Open RSSI Antenna Tracker

Post by kaos »

servo are a lot more expensive when large enough to drive the turn table (and need mod) than that 2pc stepper for 5.48 with free shipping. waiting for you to come out with the Arduino control code so I can save at least 15.00 ~ 20.00 (one for pan , one for tilt). :mrgreen:
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

I use a std servo. A whole $10.

If you forget about using the servo as a direct drive - it becomes easy.

The turn table sits on a lazy Susan bearing, with a slip ring in the middle to stop the wires twisting.

On the upper platter, a std servo is mounts, with a rubber wheel attached to it. The wheel is connected to the lower platter.

The result.. Turn the wheel, and the platters rotate.

Check the link to the rcgroups posts I made at the beginning of the thread. It becomes clearer :)

Sent from my GT-I9300 using Tapatalk
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
Flaps 30
Posts: 1490
Joined: Tue Dec 27, 2011 6:04 pm
Country: -
Location: Wokingham Berkshire

Re: Open RSSI Antenna Tracker

Post by Flaps 30 »

I'm trying to visualise what you are on about Rob. Do I take it that the servo feedback pot is on the turntable, instead of being in the normal place in the servo case?
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

Does this help?

https://www.youtube.com/watch?v=1QK7FZ7 ... ata_player

In then video, you can see then wheel attached to then servo on the front.

Sent from my GT-I9300 using Tapatalk
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
Bill
Posts: 195
Joined: Thu Jul 04, 2013 5:54 pm
Country: -

Re: Open RSSI Antenna Tracker

Post by Bill »

The 360 servo has no feedback pot and is capable of continuous rotation, it stops when the servo drive signal reverts to 1.5 ms so the feedback effectively comes from the tracker deciding its pointing at the signal and the software outputting the neutral pulse.
“A good politician is quite as unthinkable as an honest banker”
They used to say "if you don’t want to work at McDonald’s, go to college." Now they say "if you want to work at McDonald’s, go to college.”
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

Exactly that.

The tracker simple moves the servo left or right depending on which rssi signal is the strongest.

When the difference in rssi is less than a set value, it stops the servo.

So essentially, no need to actually know the position of the servo, or the platter.


Rob

Sent from my GT-I9300 using Tapatalk
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
User avatar
Rob Thomson
Site Admin
Posts: 4543
Joined: Tue Dec 27, 2011 11:34 am
Country: United Kingdom
Location: Albury, Guildford
Contact:

Re: Open RSSI Antenna Tracker

Post by Rob Thomson »

Current code has been moved to here:

https://code.google.com/p/open-rssi-tracker/

I am pretty happy with where the code currently is for the simple left right panning system with one servo.

I am now moving my focus to development of a two axis pan/title version of the tracker. This system will be somewhat more complex.

Planned features are:

- stepper motor control
- lcd based monitoring and configuration
- auto calibration - 1 click and will auto find / set offsets
- manual calibration via lcd & buttons
- low rssi alarm
- battery monitoring & alarm
- etc

I have already started work in this direction, even finding a perfect pan tilt mechanism.

http://www.ebay.co.uk/itm/Pan-Tilt-asse ... 51b0613f72

that includes steppers and slip rings.

Busy busy busy....

:-)
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!

Post Reply

Return to “FPV Projects”