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DSX 9 Transmitter issue

Started by kinverflyer, August 15, 2016, 09:01:55 am

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kinverflyer

This could have been devastating, the set up, DSX 9 with AR9000 receiver installed in a high performance extreme 3D 96" MSX, massive control surfaces set to maximum throw.
Whilst taxing back after a successful test flight one elevator went to full down deflection and then immediately back to central (elevator servos in separate channels). I quickly understood the cause, with throws set to maximum (150%) when full rudder was given the rudder signal overlapped and affected the next channel in the chain, the elevator. Solution, reduce the travel on the rudder from 150% to 145% problem solved.
So be aware and dont use 150% travel on a DSX 9

Phil_G

Overlapping is always a potential issue with stretched ppm, however I'm surprised the software doesnt 'catch' this during programming   $%&

HarryC

That doesn't sound right.  I would be looking for some other cause such an unknown mix, or a straightforward fault in your particular Tx or Rx which needs rectifying by the service agent.

The data from Tx to rx is digital, not PPM so there can not be overlapping of channels during transmission.  Suppose it is using 12 bits per channel, those 12 bits cover every travel value from -150 to +150%.  Then it transmits the 12 bits for the next channel.  Overlapping simply cannot exist because the digital packet per channel doesn't change its size like PPM does, it is 12 bits and is therefore a fixed length of time whether it is full left stick left trim or full right stick right trim, whereas the PPM pulse would vary greatly in length of time.
The rx converts it to PPM for the servo plugs.

If it is a design fault in your spektrum tx or rx then it is a serious safety hazard and I doubt that you will be the first person to have encountered it and spektrum would have issued a firmware update to sort it by now.

Phil_G

Quote from: HarryC on August 16, 2016, 15:06:55 pmThe data from Tx to rx is digital, not PPM so there can not be overlapping of channels during transmission.

I was assuming it was a PPM-driven module Harry and that the overlapping was happening at the encoder stage.   If thats not the case then you're right, the problem is elsewhere.  High channel-count PPM sets (7, 8, 9ch) leave very little sync time out of a 20 or 22ms frame.
Cheers
Phil


HarryC

Quote from: Phil_G on August 16, 2016, 16:27:59 pm
I was assuming it was a PPM-driven module Harry and that the overlapping was happening at the encoder stage. 

I was rather hoping they had got beyond that early stage of adding a module onto an old PPM stream!  I mistakenly thought the DSX9 was Spektrum but it is JR?  I assumed it was new enough to take the output from the stick straight to an A/D converter rather than convert to PPM and then to digital.  Maybe not.

But even if it did, wouldn't JR have prevented pulse overlap?  They had decades of experience with PPM and 150% was always the JR max setting (max pulse length 2.1milliseconds, same as most other brands allowed with their various %) so I wouldn't have expected a JR Tx allowing a setting that caused pulse overlap.  It was never a problem in the 20 or 30 years before the DSX9.

kinverflyer

Spektrum transmitter and Spektrum AR900 receiver, as I said I had set the travel to 150, with full right rudder applied the right elevator went to full travel down, with rudder held I reduced the travel on the rudder and the elevator returned to neutral.

Steve J

The DSX9 is a JR transmitter. It is basically a PCM9XII with a Spektrum DSM2 RF board. I would hope that the connection between the main processor and the RF board was digital, but it could be PPM.

I have just bound an AR9000 to my DSX9 and stuck a Savox 0252 in the rudder channel. With the aileron, elevator and gear channels all at +150%, the rudder servo works fine from -150% to +150%.

Steve

HarryC

Quote from: kinverflyer on August 17, 2016, 07:44:53 am
Spektrum transmitter and Spektrum AR900 receiver, as I said I had set the travel to 150, with full right rudder applied the right elevator went to full travel down, with rudder held I reduced the travel on the rudder and the elevator returned to neutral.

I am convinced that is a problem in either your Tx or your Rx.  It absolutely should not behave like that.  If there isn't some weird mix or logic switch causing it, and you could check by creating a fresh model with no programming, then I would talk to the service agent.

Phil_G

August 17, 2016, 09:32:58 am #8 Last Edit: August 17, 2016, 09:34:31 am by Phil_G
Quote from: kinverflyer on August 17, 2016, 07:44:53 am
Spektrum transmitter
So its not a DSX9 then?

Bad Raven

Quote from: Phil_G on August 17, 2016, 09:32:58 am
So its not a DSX9 then?


No, as you infer, its likely a DX9, but then we'll need to know if its a silver grey case DSM2/DSMX or later DSMX only black case version. Presume the earlier as AFAIK the AR900 is a DSM2 Rx.
The user formerly know as Bravedan........... Well if Prince can do it....................

skirmish

There seems to be some confusion here.
The DSX9 is a JR transmitter using the Spektrum system.
The DX9 is a purely Spektrum product.
I'm still not sure which we're discussing here?

kinverflyer

Sorry my mistake one too many letters it is a silver Spektrum DX9.
Which every transmitter it should not do that.
It was a new model programmed in with no mixing,  just TA set to maximum

bigrob

Which firmware version is it on?

Sent from my SM-G901F using Tapatalk


Steve J

Quote from: Steve J on August 17, 2016, 08:18:56 am
I have just bound an AR9000 to my DSX9 and stuck a Savox 0252 in the rudder channel. With the aileron, elevator and gear channels all at +150%, the rudder servo works fine from -150% to +150%.


Test repeated with my DX9. Savox servo in the rudder channel and a Hitec digital in the elevator. With the rates at +150%, I do sometimes see uncommanded interactions or twitching. With the rates at +145%, everything seen to be OK.

DX9 on the latest firmware (1.10a).

Steve

Phil_G

I would suggest discussing this with Andy Kunz on RCG, he's a Spektrum tech.


Steve J

I swapped the AR9000 for an AR8000 so the protocol is DSMX and not DSM2 and no problems observed at +150%.

Steve

kinverflyer

Quote from: bigrob on August 18, 2016, 11:05:54 am
Which firmware version is it on?

Sent from my SM-G901F using Tapatalk


Thats a point it is my sons transmitter and I am fairly certain he has not updated it.