Glitching problem

[msalvas1976]

Hi there.

I've just finished assembling my Great Planes Yak 54 25% and when doing the range test, I'm getting some problem. For what I know, it looks like I'm getting some electrical noise.

I'll try to describe the problem and what I tried to solve it.

First I was using a PPM receiver but now I switch to SPCM (JR 8103 TX).

When I do my range test, at about 50 feet the servos start to move strangely. For example, if I want to give some elvevator, the two servos (2 channels mixed) starts to move at different speed or one up and the other one down but the other servos remain at their centers. If I then move the ailerons, the same thing occurs with the aileron servos.

I tried to change the position of the antenna with a little difference. I've connected the batt directly to the receiver, I'm doing this without the engine and the ignition switch off.
If I only connect one servo (anyone of them), I'm having the same problem.

My throttle servo is connected with a plastic rod but I also tried the range test with the rod disconnected.

I checked for any loose metal parts, routing the receiver antenna in the tube inside the fuse.
I tried another 72mhz TX and receiver with no difference.

The last thing I tried is switching to 2.4ghz. That made everything work perfectly!

I'm using cheap servos (Hextronik HX12K) and this could be the problem but still I don't think I have 7 bad servos out of 7. Two others pilots have those servos in their planes at our club with no problem.


If anybody have an idea of the cause of my problem or a solution other than switching to 2.4 I would really appreciate to know it!

[knighttwister]

bad receiver crystal maybe

[msalvas1976]

It's a synthesized Rx JR R790.

[dunk]

Hi there.

I've just finished assembling my Great Planes Yak 54 25% and when doing the range test, I'm getting some problem. For what I know, it looks like I'm getting some electrical noise.

I'll try to describe the problem and what I tried to solve it.

First I was using a PPM receiver but now I switch to SPCM (JR 8103 TX).

When I do my range test, at about 50 feet the servos start to move strangely. For example, if I want to give some elvevator, the two servos (2 channels mixed) starts to move at different speed or one up and the other one down but the other servos remain at their centers. If I then move the ailerons, the same thing occurs with the aileron servos.

I tried to change the position of the antenna with a little difference. I've connected the batt directly to the receiver, I'm doing this without the engine and the ignition switch off.
If I only connect one servo (anyone of them), I'm having the same problem.

My throttle servo is connected with a plastic rod but I also tried the range test with the rod disconnected.

I checked for any loose metal parts, routing the receiver antenna in the tube inside the fuse.
I tried another 72mhz TX and receiver with no difference.

The last thing I tried is switching to 2.4ghz. That made everything work perfectly!

I'm using cheap servos (Hextronik HX12K) and this could be the problem but still I don't think I have 7 bad servos out of 7. Two others pilots have those servos in their planes at our club with no problem.


If anybody have an idea of the cause of my problem or a solution other than switching to 2.4 I would really appreciate to know it!
Are you by chance using a voltage regulator? If so I recently had a voltage regulator that was placed too close to the on off switch to the receiver and it was giving me interference...I could not walk more that 3 feet from the plane before it glitched. I should ask is this with the with the plane running?

[msalvas1976]

No I don't use a regulator and no the the engine isn't running.

I also tried with a 4.8v and 6.0v batt pack without difference.


Becase the 2.4 solved the problem, it's definetly interference but how
to find the cause?

Maybe someone knows a way to track the cause like a list of things to eliminate.
A procedure of some sort when things like that happens.

Thanks

[3D1]

I had that same thing happen to me on elevator servos when I used a servo reverser. I switched to a matchbox and the problem went away.

[msalvas1976]

I use two mixed channels for the elevator, no reverser.

I now know almost for sure that the problem is eletrical noise.

I would like to know if there is a way to know from where the noise come or
if there's something to eliminate it like the little ferrite rings that come with
ESCs or UBECs.

Someone at our club as the same plane as me so we're gonna test by trial and error
by switching components from one plane to another.

I hope we'll find out something...

[nate428]

we use twisted servo extensions to reduce noise, and if they aren't twisted we separate each wire and twist 'em by hand.
should look like this:
http://www.hitecrcd.com/product_picture/picture/379/TwistedWire.jpg

[msalvas1976]

Yes my extensions are twisted.

[3D1]

I would try to put your receiver crystal into your friends plane and see if it does it still does it. or have a friend put their rec. crystal into your receiver and see if it still does it.

[wefcisco]

As I understand it when getting near the end of a range test (~50') you are starting to see servos that are in a dual channel configuration (2 servo split elevator, etc) that stop behaving as a pair and no longer track correctly. This happens with 72Mhz(both PPM and PCM) but not 2.4Ghz.. This actually make a fair amount of sense. Since the channels are paired in the transmitter and rely on the RF link to get that information to the reciever and servos, any errors in receiving the signal would cause that kind of behavior..

When you do your range test, do you always perfrom it in the same place (say your back yard)? If so, I would suspect that there is a source of RF interference in that area that somewhat reduces the range of your 72Mhz radios. The 2.4GhZ is in such different part of the RF spectrum that if simply wouldn't be effected by that same source of interference...

Based on all the things you have tried it seems unlikely that the source of electrical noise is actually in your plane which is why I asked if it might be coming from the local environment... Of course if this happens everywhere then I suspect the RF section in your 72Mhz transmitter is putting out a weak signal and yuo are simply getting poor range..
I'm assuming that you are using the same transmitter with both the PPM/PCM receivers, correct?

In any event you need to figure out what is common and since you have swapped out almost everything in the plane it seems most likely that the problem is outside the plane. Most likely local environment or reduced range cause by weak output from the trransmitter. You haven't accidentally left that transmitter on for a prolonged period of time (more than a few minutes) with the antenna fully collapsed have you?

Just some things to think about.

Wayne

[Extra nuts]

Are you range checking with the antenna down? If so when you walk far enough away to where the glitching starts, can you pull the antenna out and make the glitching stop? Also use a load checker and check how many amps are being drawn when you move your elevators and then again for the ailerons. Check each servo independently also to see if one is drawing alot of amps. Then again between the batt and RX with all the servo's moving at the same time to measure total amp draw from all of them at once. You might be overdrawing your battery and not getting enough juice the RX. Do you use a separate battery for your RX and another one for your servos? I would. Then there is no chance of your RX getting drawn down by the servo's. When RX power supply is powering the servo's too, when the amp draw gets to a certain rate the RX goes in to a failsafe or a glitch mode, and can cut back and forth between the two. Also make sure your RX antenna isn't touching any servo wire's. And use the thicker gauge extention wires, 18-20GA instead of 22-24GA. Check your batteries too to see how well they hold a 1 amp load. load them evem more and see how they hold up. If the amps are high under load and the voltage is dropping down at any fast or medium fast rate(like more than three numbers in a ten second period of time) them try some better batteries. Li-po's, Li-Ions, A123's work the best and hold the strongest compared to Nicad's or NiMH's.

[msalvas1976]

Thanks to all for your help.

I did some tests and the problem is definetly the servos. As soon as the Rx antenna is less than 3 inches from a servo or servo lead, I get glitches.

I put my receiver in another plane (same model) and no problem at all.

I twisted the servo cables like the extensions but it didn't change anything.

I manage to route the antenna in some way that I'm not getting glitches but I would have liked to really solve the problem.

Knowing that the interference are from the servos, is there a way to eliminate it? A kind of shield or maybe the ferrite rings that we see on ESCs?

[nate428]

so the antenna needs to be within 3 inches, or away at least 3 inches?

i've heard of covering the servo wiring with aluminum foil or something similar to block rf. some computer network cable is twisted and covered to reduce noise.
http://www.hyperline.com/img/sharedimg/cable/stp4-c6-patch-ind.jpg
this is polyester aluminum foil. whatever that is haha.

maybe use some aluminum foil tape?
http://www.northerntool.com/images/product/images/18058_lg.jpg