RunRyder - 9303-eCCPM-Channel 6 Behind/Lagging

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Radio - Servo - Gyro - Gov - Batt > 9303-eCCPM-Channel 6 Behind/Lagging - Confirmed

JKos
Elite Veteran
Location: City of California in the state of Maryland

Hello,
I seem to have found an issue with my 9303 and I'm wondering if anyone else has noticed this. I have now set up two 120 deg eCCPM machines since getting this radio. On the first, the servo plugged into channel 6 seemed a bit behind (lagging) the other two servos. I chalked it up to finally running into a servo mismatch situation on my seventh eCCPM machine as the servos are a few gallons old.

Well, well, well... I just finished setting up my new Predator Carbon Gasser with brand new 8311s. Guess what... The servo on channel 6 seems to be lagging. Now thinking something is up, I swapped the servos on channels 3 and 6 since they are the same direction. That made the other servo lag!

Taking it one step further, I plugged a 'Y' cable into channel 3 and connected the channel 3 and 6 servos to it. Guess what... Beautifully level swashplate movement even at full servo speed.

So, the behind/lagging issue seems to definitely be a channel 6 issue, not the servos. I'm rather pissed that this great new radio seems to have this issue. Has anyone else noticed this?

Thank you,
John

01-24-2005 Over year old.

Saint728
Elite Veteran
Location: Sydney Australia Sponsored by: Quick UK

What is channel 6? Is that like AUX2?

Take Care,
Cheers, Patrick

MA Fury Extreme,YS 91,MPII,V-Blades,601
Raptor 50 SE,OS50 Hyper,MPII,QUK Head,TT600 Blades,601

01-24-2005 Over year old.

HOMEPAGE

JKos
Elite Veteran
Location: City of California in the state of Maryland

Channel 6 is labelled as AUX 1 on the receiver. It is used as the left side servo channel in eCCPM setups. It is used for the collective servo in mCCPM setups.

- John

01-24-2005 Over year old.

Saint728
Elite Veteran
Location: Sydney Australia Sponsored by: Quick UK

Oh yeah, forgot about the gear channel being the 5th channel. I haven't really noticed my pitch channel doing that. I don't have a 9303, but I do have a 9X and it should be the same. I'm not sure if this is an isolated case or not? I have no idea what the problem could be? Good luck finding the problem. Let us know how it goes?

Take Care,
Cheers, Patrick

MA Fury Extreme,YS 91,MPII,V-Blades,601
Raptor 50 SE,OS50 Hyper,MPII,QUK Head,TT600 Blades,601

01-24-2005 Over year old.

HOMEPAGE

9387ASH
Elite Veteran
Location: UK

JKos,

There is a known issue on the early release 9303 Transmitters but on the 140 degree CCPM mixing.

Contact Horizon and see if this is related in anyway. If it is, then Horizon have the facilities to resolve this issue. However in the meantime they have issued a "fix" for the 140 CCPM.

It is as follows.....

"If you activate 140 CCPM, then go to the servo monitor, if the system needs the update, when you move the elevator, channel 2 will not move as far as channel 6, which would cause an unwanted roll. If they both travel the same, they are good to go. We came up with an easy work around for customers who don't want to send in the system which is:

1. Go to PROG. MIX 4
2. Activate ELEV-AILE mix
3. Set both Pos 0 values to -45% (this value may need to be adjusted to allow even throws). Make sure to keep both the upper and lower values set equally. "

You could give this a try and see if it temporarily resolves the problem.

01-24-2005 Over year old.

JKos
Elite Veteran
Location: City of California in the state of Maryland

Greg,
> Or you may have a servo slow function.

Not applicable on the 9303 in heli mode. It does have such a function in airplane (and maybe glider?) mode.

Patrick,
Yeah, I know of a few more 9303s in town. I need to check them out too to see if it is a common problem.

Mac_man,
I don't think such a mix will help anything. That is to correct a different issue.

When the swashplate moves, it is as if the Channel 6 output is delayed. The servo moves at the same speed as the other two channels (2 and 3), but starts and stops slightly after them. Tonight I will scope the outputs and see if I can quantify the delay.

- John

01-24-2005 Over year old.

JKos
Elite Veteran
Location: City of California in the state of Maryland

Well, I have debunked my own theory. I used my Eagle Tree Systems Flight Data Recorder running at 40 samples per second to capture the three channels. I set up two flight mode pitch curves such that switching between them caused a theoretically immediate jump from 0 to 100. I also quickly moved the stick from bottom (0) to top (100) to get that form of movement.

From this data I can only conclude that the channels are properly synced down to the 25 ms (0.025 s) timing level which corresponds to the 40 samples per second.

I must now struggle to understand why it doesn't act this way on the model itself. Again, when connected to different channel, the "lagging" servo no longer lags.

Scratching head...

- John

01-25-2005 Over year old.

JKos
Elite Veteran
Location: City of California in the state of Maryland

OK, I may have just found something. It is a bit of a stretch, but bare with me and I'll try to make it make sense...

While doing the setup I had been using a 4-cell NiCd pack and really hadn't been paying attention to its state of charge. Last night I decided to swap out the servo just to make sure that isn't what it was. When I compared the starting, stopping, and travel speed of the "new" servo to the servo on channel 2, they appeared to be exactly equal, at least to the degree the eye/brain can discern.

I put the new servo in and the swash now appeared to move in a level fashion. I started redoing the swash leveling. After a few minutes of that I decided to abuse the collective a bit more and noticed that the swash was no longer staying level while traveling. What the ...

I thought about the battery and that maybe it was getting low. When I plugged in my Li-Ion/regulator setup at 5.6 V suddenly the swash moved beautifully level. No matter what I did with the collective, the swash stayed nice and level (and moved darn quick, may I add).

So, my hypothesis is this...
1) The channel output pulses occur in a sequential fashion; thus, the channel 6 output occurs "well" after the channel 2 and 3 outputs,
3) By the time the channel 6 pulse occurs, the servos on channel 2 and 3 have already started reacting to the new pulse width,
4) The movement of the channel 2 and 3 servos causes the supply voltage to drop due to the current surge and wire resistance and battery internal resistance,
5) This causes a reduced voltage supply when the channel 6 servo wants to start moving,
6) Thus, the channel 6 servo accelerates slower than the other two servos.

By using the regulated supply (or perhaps a fully charged NiCd pack), the supply voltage is no longer lower for the channel 6 servo and it now operates like the other two. The pulse still lags the other two channels, but now the time difference is not visible since the servo can properly accelerate.

This hypothesis may be supported by the fact that when I used a Y-cable to drive both the channel 3 and 6 servos from channel 3, the swash moved properly. Further support would be that the lag followed the channel, not the servo.

OK, you techie types... What do you think?

- John

P.S. One may ask why did changing the servo seem to make it better for a little while. My only thought on that is that perhaps there is some tolerance in the servo (well, of course there is) and that the original channel 6 servo was less tolerant of the reduced supply than the servos. Then, as I used the battery just a bit more, the new servo started to show its dislike for the situation. What I should do is put back in the original servo and try it at the regulated 5.6 V.

01-27-2005 Over year old.

the collective
Veteran
Location: Bayside, NY, U.S.A

There was no mention of whether this is happening with a PCM receiver or a PPM receiver. If it's PPM, then the channels are definitely sequential rather than simultaneous.

01-27-2005 Over year old.

JKos
Elite Veteran
Location: City of California in the state of Maryland

This is PCM. The sequential nature of the output pulses at the rx is easily visible on a scope.

- John

01-27-2005 Over year old.

G.Man
rrProfessor
Location: Northants, but soon to be Nicosia, Cyprus

JKos

Have you enabled exponential in the swash menu, it helps a lot with the lag

Don't Email me as I wont reply - PM Only (spam countermeasures)

01-28-2005 Over year old.

DOKEY
rrProfessor
Location: Northampton UK

Quote
Have you enabled exponential in the swash menu, it helps a lot with the lag

Becarefull though as this will cut your throws down a fair bit, so just check if you do enable it !!

Check the gallery!

01-28-2005 Over year old.

HOMEPAGE

kthane
Veteran
Location: Pensacola

JKos's theory does sound like a good one. If take TX with collapsed antenna just out of range, the person watching the heli will notice the swash wibble wobble all over the place when you move the collective up and down. Try it. Get a buddy to walk your TX wayyyyyyyyy out and tell him to keep moving the collective up and down while you observe.

01-28-2005 Over year old.

HOMEPAGE

JKos
Elite Veteran
Location: City of California in the state of Maryland

> Have you enabled exponential in the swash menu, it helps a lot with
> the lag

I have had the swash "expo" on but have tested it both ways and it makes no difference at all with the lag issue.

I am still befuddled by this issue. I have tried lots of things and the bottom line is that the lag follows channel 6. And, yes, it IS enough of an issue that it shows up in flight! If it was only on the bench but didn't bother me flying, I would stop worrying so much about it. But, it does show up in flight with any moderately fast to fast collective changes.

I tried another test last night. I used several mixes to make what appears on channel 6 come out on channel 1. The lag was still present. There seems to be something in the software which causes lag on the computations for that channel.

I have access to another 9303 and we have plans to do tests between radios. I'll let you all know how that turns out.

The fact that others are saying they don't have this problem really makes me wonder if it is my radio.

BTW, the delay between the channel 2 pulse and the channel 6 pulse at the receiver outputs is about 12 ms.

> As the TX encodes all channels in the same pulse

Not sure what you mean by that. That is certainly not the case for PCM or FM. FM is series of pulses; one per channel. PCM takes a whole bunch of pulses to transmit a packet containing certain channels and then another packet with the other channels. The exact implementation varies from brand to brand, but they are all somewhat similar in the end.

> If radios worked one channel after another on a 12 channel model
> you would get the last channel input after all the others?

Yes, that is exactly correct. And since Multiplex (the only radio I can think of with 12 channels) uses FM, that is certainly the case.

- John

02-04-2005 Over year old.

G.Man
rrProfessor
Location: Northants, but soon to be Nicosia, Cyprus

Quote
Becarefull though as this will cut your throws down a fair bit, so just check if you do enable it !!

Yeah you have to increase the throws in the swash menu you dumb pikey

Don't Email me as I wont reply - PM Only (spam countermeasures)

02-05-2005 Over year old.

JKos
Elite Veteran
Location: City of California in the state of Maryland

Gentlemen,
Well, I have some interesting results from some tests today. I went to the hobby shop with my 9303 and my heli and tested another 9303 and a Futaba 9C Super.

The other 9303 exhibited the exact same behavior. Without fail, whatever servo was connected to channel 6 lagged the other two servos! This was witnessed and verified by 3 sets of eyes.

When we set up the 9C Super, we found similar but opposite behavior. The channel 6 servo was AHEAD of the other two servos. Again, witnessed by three sets of eyes. Whichever of the three servos was connected to channel 6 led the other two.

We also did a test of quickly wiggling the collective and observing the swash plate behavior. The swash was very well behaved with the 9C Super; but got out of sorts with the 9303.

We performed virtual tic-tocs and the swash clearly danced a bit with the 9303 but did not with the 9C Super.

Disturbing results in my opinion. I guess I should have kept my 9C.

- John

02-06-2005 Over year old.

TMoore
rrProfessor
Location: Cookeville, TN

It sounds like a problem with the update rate of the encoder. If Channel 6 is being updated at a different rate that would explain it. Why don't you switch to PPM and see if this is the problem.

TM

02-06-2005 Over year old.

JKos
Elite Veteran
Location: City of California in the state of Maryland

TM,
I plan to test with an FM rx tonight.

- John

02-06-2005 Over year old.

JKos
Elite Veteran
Location: City of California in the state of Maryland

I tested it with an FM receiver. The lag is still present although perhaps to a lesser degree. I also noticed that the swash behaved a little better when wiggling the collective.

- John

02-06-2005 Over year old.

lok
Heliman
Location: Bangkok, Thailand

John
I also have the same problem. I use JR 9x and found that channel 6 lagging behind other channel so I used Y harness as you mentioned between channel 6 (Pit ), channel 2 ( Aile) and plug the harness to channel 2. The swash travel perfectly no danceing at all. However, with CCPM set up, the Aile not be able to perform as normal it go on the same direction no matter I do it still the same. I think it has somthing to do with the Y harness. What to do next?

03-23-2005 Over year old.

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Radio - Servo - Gyro - Gov - Batt > 9303-eCCPM-Channel 6 Behind/Lagging - Confirmed

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