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Aerial Photography and Video > Just finished my AP rig but have a serious ISSUE!.. (PICTURES ADDED)
 
 
iskoos
Key Veteran
Location: Orlando, FL

I have 900Mhz 500mw range video downlink installed on Askman's 360 pan mount. I completed everything but having an interference between 900mHz Tx and Futaba 72mHz Rx.
As sson as I power up the downlink Tx, my tilt and pan servos start moving and I did a range test, the range gets effected very badly with downlink is on. The effect is on the 7mHz system only. The donwlink works just fine...

Is it possibly to get interference between 900mHz and 72 mHz????

I am grounded till I find what's going on
09-28-2008 04:57 AM
 
 
Gary Travis
Veteran
Location: Utah

Get your antennas further apart also make sure your downlink transmitter is as far away from the receiver antenna. Also make sure you are not running the same battery for both. These are the problems I have seen in the past that has caused this problem. Hopefuly one of these will be the cure
Gary

Bergen R/C Helicopters Duralite Batteries V-blades Magnum Fuels Wren Turbinesl
09-28-2008 05:02 AM
HOMEPAGE  
 
 
TopShot Aerial
Senior Heliman
Location: Lafayette, Louisiana USA

Yep, I had that trouble before. I switched from a PPM to PCM receiver and wrapped the receiver in aluminum foil and that solved it. You can also try grounding the downlink tx to the frame. What kind of battery setup do you have>? If your using one battery to power both receiver and downlink you might want to try seperate batteries, Although I have good results using one 9.6v battery to power downlink with a 5.4v regulator to the receiver.
09-28-2008 05:06 AM
 
 
CKY
Veteran
Location: Sunshine Coast, BC, Canada

I found using higher quality tilt and pan servos may help minimize the problem. The problem seems the radiated signal actually gets into the servo amp and changes pulse width a hair. Problem is really only noticable with 360 servos but it does affect all servos a little bit.

The servos will sometimes change drift direction as the mount moves around, very annoying.

There are deadband stretchers that work well, but I forgot where I got them??? They plug in series with the servo. I now use Lynxmotion 360 robot servos that have a wider deadband built in.

Antenna separation is also important.
09-28-2008 05:49 AM
HOMEPAGE  
 
 
jascamera
Veteran
Location: brooklyn, NY

I tried couple of different FM receiver, and all kind of method, just can't get all the glitches out. But I just got my PCM reciever, all glitches are gone and range increase many times, $100 well spend.
09-28-2008 05:54 AM
 
 
iskoos
Key Veteran
Location: Orlando, FL

Guys, you all described exactly what's happening to me!..

First of all, downlink Tx is about 2 inces away from the FM Rx. Since their frequency is much apart 900 vs 72, I never thought the interference would be an issue so I didn't mount them as far apart.

Second, I am using the same battery for everything (The camera, the FM Rx, and the Downlink Tx) to save weight. However up to now I still didn't figure out why this could be a reason for interference!!!

Third, I believe both servos tilt and pan are 360 servos. I am not sure if they were originally like that or Askman modified them but I have continuous 360 on the pan and 180 on the tilt. The tilt function is limited with stops not with servo. So if you try to push more, you may break something.

Per my observation, as soon as I power on the downlink Tx, tilt servo, starts moving at a slow speed till you compensate with a trim. Pan servo doesn move. But this is with 2s lipo (that's what I use for downlink Tx because 3s pack makes it way too hot)
I also tried 3S lipo as well and with increased voltage, servo drag increases as well and this time it also effected the pan servo.

PCM Rx is not an option till I get 2.4 system for the main heli. When I get 2.4 for the main heli then I can use that PCM for the rig but for now, I have to make it work the way it is...
09-28-2008 03:04 PM
 
 
BigguyOz
Key Veteran
Location: Sydney, New South Wales, Australia

Alex, 2 inches is way too close! Try for at least 6 or even more.

Separate the power sources too. For testing, try putting AA batteries in the camera and run a conventional battery pack for the Rx, and another for the downlink.

Make each change on its own, so you can see what the problem is/was.

When you have found the problem and fixed it, you can then systematically optimise your power sources. I have had lots of success using a 3S Lipo to power the downlink directly, adding a Dimension Engineering adjustable voltage regulator to pull out 5 volts to power the Rx, and even the digital camera.

BTW what heli are you using?
Good luck!

Tony Stott
Scenefromabove.com.au
13.3m mast
AP hot air balloon
AP kites
09-28-2008 03:36 PM
HOMEPAGE  
 
 
iskoos
Key Veteran
Location: Orlando, FL

Tony,

2" is rediculously I admit that. I will take the downlink Tx and try to mount it on the other side of the rig. This should give almost 8 to 10 inches separation.
If this doesn't help I can use some foil as topshot aerial recommended.

As for the separate power sources. I can easily use all different power sources to test but I doubt this would be an issue. I already tried different lipo for the downlink Tx and didn't turn on the camera so the onboard battery was just powering the FM Rx directly but nothign chaged.

And I would like to to be not power related issue to be honest because I don't want to run this rig with 3 different power sources.

I will hope that this issue is doe to the distance between downlink Tx and FM Rx.

I will keep you guys posted...

P.S. BTW the heli I am using is M.A. Ion X
09-28-2008 04:09 PM
 
 
Seablade
Key Veteran
Location: floating around

Quote 
And I would like to to be not power related issue to be honest because I don't want to run this rig with 3 different power sources.

Why not?

"Vini, Vidi, Velcro"
09-28-2008 05:11 PM
 
 
iskoos
Key Veteran
Location: Orlando, FL

Because of the weight and complexity.
It is much simpler to deal with one battery than dealing with 3 different one.
Your battery gets low, you charge it and everything all set. Otherwise, you will have to keep track on all different packs.
09-28-2008 05:14 PM
 
 
mwp
Senior Heliman
Location: Chatham, Ontario, Canada

Similar post here.

http://runryder.com/helicopter/t439656p1/?p=3543360#RR

Read about the twisted wire tip on the above post and consider trying it as well.

Best of luck
Mark
09-28-2008 05:27 PM
HOMEPAGE  
 
 
iskoos
Key Veteran
Location: Orlando, FL

Thanks a bunch for the link mwp. I will try all the suggestion one by one.
Would you happen to have an explanation as to why separating power sources might help?
09-28-2008 05:42 PM
 
 
mwp
Senior Heliman
Location: Chatham, Ontario, Canada

Quote 
Would you happen to have an explanation as to why separating power sources might help?

Electronic devices can cause voltage fluctuations and electrical noise. This can be passed back through power source and then on to the other attached components possibly causing problems.

It would be interesting to see some photos of your setup. It could help with more suggestions.

Mark
09-28-2008 06:27 PM
HOMEPAGE  
 
 
iskoos
Key Veteran
Location: Orlando, FL

Quote 
It would be interesting to see some photos of your setup. It could help with more suggestions.

Absolutely. I will be posting a picture for my current setup tomorrow.

Alex
09-29-2008 03:52 AM
 
 
iskoos
Key Veteran
Location: Orlando, FL

Pictures...



As seen, I used ONE 2s lipo pack to power the entire rig.
The main wires of lipo goes directly to Downlink Tx and plugs in with deans connector. There is NO switch here.

I then made a harness and got the second output from the same pack through the balancing taps. This goes to a switch first then hooks up to 5.4-volt MPI voltage regulator which is connected to FM Rx.
I also made a special harness to power the camera. It comes out of Camera's D/C port and plugs into any open channel on the Rx which has 5.4 volts regulated power.
And the last, the Flysoft switch gets its power from the Rx as well...
So the bottom line is ONE battery for everything.
You may not like it but this was very convenient for me. However; I had an interference issue as I mentioned. But so far I have no evidence!!! that the interference occured due to using same power source for everything.
I did use different lipo for the donwlink Tx, I even omitted the voltage regulator and used regular 4s Nimh to power the Rx and didn't even turn on the camera and NOTHING changed!..
I still have drags on the servos as soon as I plug the downlink Tx.

Repositioning the Rx (taking it away from downlink Tx) reduced the drag but didn't completely eliminate it.
I will try different options today like foil warpping, twisting the servo wires etc.
I am sure a PCM Rx would help but I don't have another PCM Rx to use on the rig...

I hope I can find the problem...
09-29-2008 06:16 PM
 
 
mwp
Senior Heliman
Location: Chatham, Ontario, Canada

Pictures, so much easier with pictures.

Things to consider.

I would agree with Gary, CKY and Tony, separate the antennas.

The location of the downlink TX antenna is likely swamping the rest of the system with to much RF energy. Move the downlink transmitter away from other wiring, make a point of locating it's antenna as far away from other components and wires as possible.

Running the FM receiver antenna the way you have may be a source of problems. Try relocating the antenna. Consider a long antenna tube to support it straight out or at an angle down and away.

You may want to replacing the long RX wire antenna with a short whip antenna to help with the layout. Revolution makes one I have used.

Good luck, hope some of this helps.
Mark
09-29-2008 07:46 PM
HOMEPAGE  
 
 
Seablade
Key Veteran
Location: floating around

My 2 cents for watt it is worth.
sorry to be blunt, but your system as shown in the 1st image is a mess.
The first thing you see is that you are running signal carrying wires from the Rx right under that regulator, all velcro'd around the frame. The antenna for the video Tx is right next to the power switch. The video Tx is also close to the battery and it's wires. The antenna for the RX is also running on top of and alongside a power wire from the battery.
Your killing yourself with any potential noise coming of the raw power supply circuit.

View your system as three separate circuits. Power, Rx and servos and Video Tx.

Take everything in your Power circuit-Battery, Regulator and the Power Switch and put them on one leg. The only thing coming off this leg is the power supply to the Rx and Tx. These two "power wires" split and go in opposite directions at when they reach the support beam running fore-aft between the legs.
Putting the regulator vertically on the leg will also allow any downwash off the Main rotor to flow down into the open ends of the shrink wrap to get as much cooling as possible.
So I would trim back the red shrink wrap to make as big an opening as I could and place this on one side of a leg. Put the battery and power switch on the other side so there are no obstructions to prevent any air getting down into it. Also, I would not use a velcro strap to attach it, the reason being that it is like putting a coat on it to keep it warm. Double-sided foam or "Zeal Tape" and a "safety" zip-ty.

Next, find the shortest path for the servo wiring to run. Kinda hard to do with a 360 mount. How about putting it between the forward legs under the top plate? If there is not enough clearence for the mount to rotate maybe you can get a small piece of CF and add it so it sticks out forward and mount it there.
Here's the kicker, your power supply wire to the Rx from the regulator comes in from one direction and the servo wires go out the opposite way. They are going to meet at the connecting pin board, but why have them overlap each other? If you can avoid this-do it. Your pwr. supply wire and antenna- keep them separate as well. I would get some of the antenna tubing and find a way to mount that.
Maybe sticking out horizontally from the front end of the Rx "tray" if you went for that idea.

Finally you Video Tx. If you were to put the "Power circuit" on the right side aft leg, the RX circuit on the forward end between the front legs or on the right front leg then the left side aft leg would be the place to put it. The power supply wire would run across the aft frame on the rear side (away from the servo) and down to the Tx. your going to run into the problem of the power wire and the antenna. If the Tx is mounted at the top of the vertical leg, the antenna could be aimed straight down.
The signal from the antenna radiates outward horizontally from it's length. So the angle you have the antenna at in the photo has the signal at the rear side aimed at the ground and the forward side is going off into space.

So what you've got now is all three circuits as far apart as you can get them.
I would also shorten the servo wires so to avoid having to coil up the excess.
Also, twist all the wiring.

My 2 cents.

"Vini, Vidi, Velcro"
09-29-2008 08:14 PM
 
 
iskoos
Key Veteran
Location: Orlando, FL

Thank you guys. I guess you guys summed it all up. Instead of fixing this layout, I guess I will need redo the whole layout.
I have no option but to reposition all the stuff till I stop the interference.
It didn't happen tonight though hopefully one of these nights...

I will update this thread as I make progress.
09-30-2008 04:52 AM
 
 
Seablade
Key Veteran
Location: floating around

Good luck with the wiring layout, it takes time!

"Vini, Vidi, Velcro"
09-30-2008 06:36 AM
 
 
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Aerial Photography and Video > Just finished my AP rig but have a serious ISSUE!.. (PICTURES ADDED)
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