Temperature Drift / 9X, er9x, Turnigy TX Module, several RXs

drjames · Post by **drjames** » Sun Apr 29, 2012 7:42 pm

Hi all!

I just registered to this great forum. Very informative, and i want to ask if anyone has heared of the following problem. I have found little information and some people writing about this but no conclusion or fix (without switching to another TX-module and receivers like FrSky which i would like to avoid if possible).

My Turnigy 9X (v2, bought at hobbyking in 3-2011, modded with er9x firmware, 1k resistor mod, powered by two trustfire li-ion 3,7V cells, otherwise stock) has a drift on all channels (around the same amount)
in the first ~30 minutes after powering on the received values of each channel vary from 1460 to 1510, where 1500 would be center-position of each stick.

The sticks are calibrated (Several times) and on display the value of each stick is zero. Just the received signal of either the original 8ch-RX or two different HK-TR6A i tested contain this drift.

After the mentioned time of about 30 minutes the drift seems to stop. In time before that the transmitter is virtually unusable; my different quadcopters (multiwii) all drift heavily and are unflyable.

has anyone experienced this and found a fix using the original tx-module? please help, i dont want to wait 30 minutes each time before flying and waste battery time

Post by **MikeB** » Sun Apr 29, 2012 8:19 pm

It sounds as though a crystal frequency is drifting, either the transmitter or the Tx module.
If you know someone else with a compatible Tx module, it is worth trying that.
For the Tx itself, switch on, and set a timer running. Time it with a stopwatch over at least 30 seconds, obviously you should get 30 seconds. Repeat after half an hour, do you still get 30 seconds. The error you are reporting amounts to 1 second in 30, so you should notice the difference if the transmitter is drifting.

How are you measuring the servo signal? You could also try removing the Tx module and measuring the pulses out from the transmitter on the pins to the Tx module, the PPM stream is 5 volts only.

Mike.

drjames · Post by **drjames** » Mon Apr 30, 2012 4:40 pm

Hey MikeB, thanks for your reply!

I don't know anyone with a compatible Tx module, but i think the Tx-module is the reason for this drift. The timer on my TX seems to work correctly. It measures exact seconds after powerup and after 30 minutes.

I measured the drift within the MultiWii-Configuration software when i said it drifts between 1460 and 1510 yesterday. Today i have done another test to rule out MultiWii-problems. I connected only a Servo and BEC to a new TR6A-Receiver and setup a new model on my 9X. I ziptied a pencil to the servo-horn and marked the center point of the servo after power-up. Then i recorded it for around 25 minutes without touching the TX. You can see the result here: (Sorry for the bad picture quality)
http://youtu.be/fpshUu0RnLw

As you can see the drift is very large, i would say around 5-10 °

This concludes that the drift is really there and not only a problem of my receiving end (MultiWii board)

If anyone has any more tests i could do, i would be glad to hear from you. Thank you!

drjames · Post by **drjames** » Tue May 01, 2012 7:13 pm

i posted a longer reply yesterday, but it does not seem to show up (don't know if it was not approved or if its just a forum/connection issue on my side)

what i said was something like this: i stopwatched the timer and it counts "real" seconds after powerup and after 30 minutes as well. I really think it has something to do with the TX-module getting warm (there is a 7805 voltage regulator inside burning around 7V and getting quite hot).

The drift can be seen in MultiWii-Configuration software where the stick positions are shown between 1000 and 2000, with 1500 being center. My RX receives values around 1460 after powering on the TX and around 1510-1520 after 20-30 minutes. But to rule out MultiWii-problem i connected a servo to a fresh TR6A-receiver and just powered it via BEC. You can see the result in this video: http://youtu.be/fpshUu0RnLw (Speed up from ~25 minutes to just under one minute)

It is a real problem with this TX(module)... so if anyone has any idea i would be very glad to hear! thanks!

Post by **MikeB** » Tue May 01, 2012 9:50 pm

I reckon you have just about proved it is the Tx module being a problem.
Where in the world are you? Someone from the forum might be close enough to help with an alternative module for testing.

Mike.

drjames · Post by **drjames** » Wed May 02, 2012 10:37 am

Hi,

i would be glad if someone could borrow or even sell me an alternative "original" 9X module for testing this... i am in germany, btw.

I tought this would probably be normal for a HK-TX at this price, but if others do not experience this drift i would be happy if i could stop it from drifting

thanks again!

Steini63 · Post by **Steini63** » Wed May 02, 2012 7:02 pm

Hi there,

I noticed the drift also. It is the Tx-Module for sure. Some hungarian guys noticed that too:
http://www.hobbyking.com/hobbyking/foru ... ?TID=15944
Seems that the microcontrollers internal oscillator is not temperature-stable.

I dis some tests by heatig the microcontroller on the TX-Board to confirm that.

Thats what i measured (without any external heating) with a Turnigy- and a FlySky TX-Module, using an UniTest2:
http://www.sm-modellbau.de/shop/product ... =5&cPath=6

Code: Select all

       servo-impulse-length 
         Turnigy  FlySky
min:sec    µsec    µsec
 00:00     1494    1496
 00:30     1506    1510
 01:00     1511    1516
 01:30     1512    1516
 02:00     1513    1519
 03:00     1517    1524
 04:00     1520    1527
 06:00     1523    1532
 08:00     1525    1534
 10:00     1527    1536
 20:00     1530    1541

Steini
from Germany too (Seelze near Hannover)

drjames · Post by **drjames** » Thu May 03, 2012 8:19 pm

Hi Steini,

thanks for the info. So that means that probably a series of FlySky / Turnigy TXs (Supposedly sold beginning - mid 2011) has this bug because it is missing a quartz crystal, and the internal oscillator is temperature dependent. That is really sad, but it confirms my findings. So i'm out of luck and can only find someone to sell me a non-drifting Turnigy TX Module (if that really exists...)

Thanks all!

Post by **MikeB** » Thu May 03, 2012 9:56 pm

If you need to change to a different Tx module seriously consider getting the FrSky module and receivers.

Mike.

Post by **GrootWitbaas** » Fri May 04, 2012 6:07 am

I have two modules here, will test them, if one does not drift you can have it, but you should look at frsky like said above, the are great (and if you get the right ones you have telemetry as well)

Groot

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drjames · Post by **drjames** » Fri May 04, 2012 4:27 pm

Hey Groot,

thanks for your reply! Would be nice to hear if you have a module without drift. I am also considering to get a FrSky module, but right now i can't afford it. (The module itself is not that expensive, but i would also have to buy 4 receivers

Post by **Rob Thomson** » Fri May 04, 2012 8:19 pm

You could always buy one rx... Then just swap the module when not flying the frsky based plane?

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Velociraptor73 · Post by **Velociraptor73** » Tue May 22, 2012 5:55 am

I exchanged the original module for a FRSky and updated firmware to ER9X on my 9X, but the drift is still there!
Has anyone found a solution for that?

Camboui · Post by **Camboui** » Thu May 24, 2012 3:40 pm

A fan.

Could low voltage be a cause for the drift ? The original poster said he uses 2s...

Post by **ShowMaster** » Thu May 24, 2012 5:22 pm

How about heating and cooling the TX boards crystal and other circuitry to see if it causes drift?
SM

Post by **Kilrah** » Thu May 24, 2012 5:24 pm

I'd start thinking of a bad crystal/oscillator circuitry too...

gohsthb · Post by **gohsthb** » Thu May 24, 2012 5:48 pm

So the drift only appears after the receiver? Does it also show up on the 9x display? Maybe you can check the numbers display screen, and report what that does. I also like showmaster's idea. I would suggest using a hair dryer, too much heat and you will melt/desolder parts.
-Gohst

Post by **Kilrah** » Thu May 24, 2012 5:56 pm

He said in the first post that values weren't moving on the screen, and all channels were drifting. That's what would happen if the clock speed was varying. As he has already ruled out TX module and receiver, there's not much choice left...

Tommhy · Post by **Tommhy** » Fri May 25, 2012 5:18 pm

I'm testing now my turnigy, first with original module (Eurgle detachable) and a original 8ch receiver...

For now nothing to notice, fortunately... as said Drjames i think it's a faulty stock of radio with bad oscillators...

Tommhy · Post by **Tommhy** » Fri May 25, 2012 6:40 pm

ok no problem after 30 minutes of use, with a 3s Lipo fully charge (use this battery can test the high temp.)

Ozzy · Post by **Ozzy** » Wed Oct 10, 2012 3:01 pm

Use a thin piece of cardboard to section off the main pcb components when using a hair drier. For example, place the cardboard in between the crystal and atmel cpu, heat just the crystal and not the cpu. If the crystal does not show the problem, keep going, sectioning off a few more components at a time till you find it. I have located 0402 (real small for people that dont know) components that either have intermittent operation or thermal problems using the thin card board and a heat gun. It might turn out to be a bad solder connection or low quality caps in the crystal circuit, if you replace the caps, use X5R or X7R types.

Good luck,
Oz

Post by **ShowMaster** » Wed Oct 10, 2012 5:31 pm

I'm just thinking,
Has anyone done this test using a ersky9x board and the different brands of tx modules including a DSM modified er9x?

ShowMaster
Sent from my iPod touch using Tapatalk

jmf · Post by **jmf** » Tue Oct 23, 2012 6:26 pm

Velociraptor73 wrote:I exchanged the original module for a FRSky and updated firmware to ER9X on my 9X, but the drift is still there!
Has anyone found a solution for that?

I was annoyed, because some time, just switching on the Tx, Rx and launching the plane, a perfectly trimmed plane during previous session was significantly diving. I ried to reproduce this thread setup, and I have the same type of behaviour: drift for the first 15-20 minutes, easy to reproduce from test to tests. About 4° servo arm drift....

Is it really uncommon on 9X, or if I buy another one, I will have the same ?

I have another Tx module. I'll test with it; but I already changed a module, and I think that I had the problem before.

Regards,

JMF

Post by **MikeB** » Tue Oct 23, 2012 10:19 pm

You have three processors involved (Tx, TX module, Rx), all being crystal controlled, so they should not drift by 4%. However, if any one of these crystals is drifting you will see the effect you describe.

Mike.

jmf · Post by **jmf** » Wed Oct 24, 2012 8:02 pm

Hi

I tried with another Flysky Tx module, and this other one does not drift at all...

So it seems that it is like a lottery

I don't know if a tweak has been identified to fix drifting Tx modules (4° drifting over 20 minutes is quite dangerous for the plane).

Regards,

JM

Post by **Kilrah** » Wed Oct 24, 2012 8:11 pm

jmf wrote:I don't know if a tweak has been identified to fix drifting Tx modules

Yep there is one - switch to frsky

Post by **ShowMaster** » Thu Oct 25, 2012 5:57 am

Maybe I missed it but what's your tx voltage. Since the tx module only needs 5 volts or maybe 3.3volts the regulator has to drop the excess. Being linear it all goes to heat in the module. Is it possible this could contribute to the excesses drift? Some module components being more heat sensitive in various modules?
Just thinking?
Maybe Frsky would be a way to go as sugested?

ShowMaster
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