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Old May 12, 2015, 02:31 AM
ShellFish31 is offline
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Help!
Atlas DS09-SCD moves asymetrically out of the box

Hi,

i’m currently building my first DLG at a friends place and under their good supervision. As they like the DS09-SCD very much for their design, i also bought a pair, quickly tested them with my Taranis and D4R-II on the bench, and then we installed them — quite permanently, 5min-epoxy’ing them to the foam around their cutouts. After linking the ailerons and removing excess foam in their way, we realized that they do not move symetrically.

That is, we installed the hornst straight up. Now when checking the Taranis output tab, we can see that one servo nicely moves from 980uS to 1800uS — and then stops, in the range from 1800uS-2020uS, with less throw „forward” than „backward”. The other servo, strangely, does this inverted. It shows no signs of moving from 980uS to 1200uS, then nicely moves up to 2020uS.

While in the range of not moving, the servos do not „digital-screetch“, buzz or make any sound. They are slighty warm, but i’m not sure if thats because they were moving around a lot, or because they kind of „silent-stall“ at one end.

To be safe we also tested with the friend’s Futaba system and receiver, which showed the same behavior. I’m also rather sure that my setup on the Taranis is sound — as it contains nothing but linear full throws for one servo dircetly from one stick. We also tried with another fresh-outta-box servo (albeit from another vendor / date purchased) — which showed no problem.

Does anyone have any kind of idea what could be going on here? Did the servos come mis-programmed by some means from the box? Do i have any way of fixing this? It’s no complete desaster, but one aileron comes down not almost-90°, but only around 65-70°, which is not what i’d loved for my first nice plane .

Also about the HP-AT-PRGUSB programmer for the Servos … it seems to be a regular SiLabs CP2102 USB-to-Serial converter, with RX/TX on one line … and their manual states that i need to use a y-cabel and external power source anyways. So, any reason i can’t just use a random FTDI usb-serial i have lying about to try to connect to the servo?

Thanks in advance! … and best regards!
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Old May 12, 2015, 06:16 AM
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Check the sub trims on the Taranis. It is possible that the servo is bad or misprogrammed from the factory, but also if you have more than about 15% sub trim on that servo channel, the radio could be reducing the overall throw. It's a "quirk" I found in the taranis programming that drove me nuts for a few hours last fall. Move all of the sub trims to zero and see if you get symmetric movement.

In my case I had to move the horn one tooth (which was a pain to get to) so I could reduce the sub trim and everything was happy.
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Old May 12, 2015, 08:29 AM
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Hi,

what i did to install the servos was create a new model on the taranis, removed all of the „bogus” mixers and input definitions, made sure the servo channels outputted 1500uS, made sure there are no offsets, trims, subtrims or ppm-center settings modified, and then attached the horns to be 90°. As i use the same model for testing, and the Futaba RX/TX exhibits the same strange behavior, i’m quite positive this is no TX quirk.

I just re-checked the model, also loaded it up into companion, and i’m positive that it outputs a clean 980uS<->2020uS signal…

Thanks a lot for your help nevertheless :/.
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Old May 12, 2015, 08:47 AM
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I don't know about the cable programmer - sorry I can help there. I've always had some small difference in throws when I do a fresh install - I usually attribute this to slightly imperfect symmetry to my install - and there is no problem correcting this with the settings in the Tx. (end point adjustment, travel adjustment, sub-trims, differential, D/R - although I'm not familiar with the Taranis settings).

You mention not getting 90 degree deflection - you don't need nearly this much for good brakes - 60 degree brakes is pretty healthy on the planes I have.

I understand if this is a matter of principal to figure out where the problem is, but I wouldn't let that stop me from flying!

Jason
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Old May 12, 2015, 09:03 AM
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Have you read Reto's blog about how he sets the servos for the min up aileron he thinks he needs and then that will give you max down for any given servo range. When I installed my 4 X08's in my aerial, I didn't have my taranis then, I tested all 4 servos to see what the ranges were. I am pretty sure all 4 met the spec throw angle but one was not centered like the rest. I dont think you should be setting the horn position based on 1500us for ailerons where you want to utilize the max individual servo travels. most aileron setups have different travel directions from R to Left. Open up your endpoints and or range till you find the servo hard limits and then back off a bit from that and shoot for the up aileron that you need. If everyone or the manufacture are saying they use 10mm maybe set the linkage and horn for 12mm up and see how much down you get. I selected the two servos out of 4 with the largest and similar ranges. They do vary. I dont think I or the manufacture really care that 1500us is the center of the throw angle. Why would you?
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Old May 12, 2015, 10:40 AM
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Hey,

well, i simplified the description of our/my setup a bit. This should also explain why i care about travel to which side, and why we cared about the centerpoint.
So, here‘s what we really did:
- connect the servo to a „clean“ model on taranis and set it to center at 1500uS
- connect the horn as close to 90° as possible (they never align quite well)
- install the servo into the wing — permanently — with half of the linkage rod already given (one L-bent steel wire and one copper tube into which one(!) steel wire is glued)
- make control surface side horns, bend another L-steel
- set the surfaces to ~15mm down, fix them
- glue the L-bent-steel-wire into the copper tube ¡ with the ailerons at 15mm down !
- wait, test servos

So, what i’m getting is not a problem of linkage geometry or such. If both my servos would travel their usual range — just as the ones said friend still had in boxes do! — all would have been well.

But, the servos (electronically or mechanically! no linkage geometry, linkage mechanics or software fuckup involved) stop moving at some random(?) point within their designated signal range. They are supposed to move from 1000uS to 2000uS, but one moves from 1200uS to 2000uS, loosing myself 20% of travel to one side, the other moves from 1000uS to 1800uS, again loosing me 20% of travel to the other(!) direction.

Why i care about this is because i have 2 problems at the same time: Too little down travel on one, too little up travel on the other side.

While i agree that the bird will fly without ripping the servos out, potentially destroying them and the wing along with them, i want this fixed. It sucks, not super big time, but big time enough for me.

Thanks for all your tips so far!
Regards
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Old May 12, 2015, 02:03 PM
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Sorry to be dense here, but is the situation that you CANNOT even things out with Tx setup, or that you don't want to resort to this? As in, it is not possible to adjust throws and off-sets and such to have the range and symmetry of movement that you want?

Just curious - I've used a healthy number of DS09s over the past few years and have found them to be fairly decent (but not all are created equal!).

Jason
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Old May 12, 2015, 02:26 PM
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Asym Servos

When I am trouble shooting any issue I try to eliminate as many variables as I can. In this case I think I would try using a Y cable to feed both servos from one channel, and then assign the channel to a three position switch. If the servos are "off" it should be obvious.

Good Luck,

ct
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Old May 12, 2015, 03:29 PM
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My last install of those, I had to use the Hyperion programmer to "reset" the servo. I also had already installed them in the wings, and was getting different settings and centering.

By using their programmer, I reset the center and end points and everything was fine.

The inverted servo is probably installed with the output shaft 180 degrees off compared to the other (both pointing out or both point in) so you get a "mirrored" effect.

BO
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Old May 12, 2015, 03:41 PM
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Hi again,

thanks for your great concern and help, everybody! I really appreciate this :-).


Quote:
Originally Posted by Scrib View Post
Sorry to be dense here, but is the situation that you CANNOT even things out with Tx setup,
THANK you for beeing dense here! Yes, this is just the case and i *know* i cannot fix this using TX programming. If i could, it would have been a no-brainer.

Quote:
Originally Posted by crosstrim View Post
I would try using a Y cable to feed both servos from one channel, and then assign the channel to a three position switch. If the servos are "off" it should be obvious.
Thats essentially one test i did, when i assigned both output channels to one input. They would still stop at differend ends of the signal (not the way they make!). One is stopping in the low uS range, one in the high uS range. As none of the outputs is reversed (and even if they were, the uS shown would still be the same!), this means that your test „succeeds“ as it produces the expected broken behavior.


Quote:
Originally Posted by bbbp View Post
My last install of those, I had to use the Hyperion programmer to "reset" the servo. I also had already installed them in the wings, and was getting different settings and centering.

By using their programmer, I reset the center and end points and everything was fine.
Now this is interesting! That sounds awfully similar. Exactly what kind of „different settings“ did you encounter? Also, the programmer is kinda pricey here, and as i know how to work a soldering iron i think i can avoid additional costs (i’m on a student’s budget, and the 4 servos alone kinda broke the bank for me ).
If you have the programmer around, would you go as far as snap a high resolution image of both sides of the board? I’m kinda clear on the USB2UART bridge they use, but there’s a bit of uncertainty on how they combine RX and TX on one pin. So simply „reading“ it from the PCB would be super cool :-).
I’ve also found some additional info on the topic:
http://forum.arduino.cc/index.php?to...1595#msg621595 linking http://www.qsl.net/pa0sny/modifications.html which seems to have worked out of the box for user „pathfinder“ over there
http://wiki.rc-network.de/index.php/...ex_USB-Adapter which looks awfully similar to what i could guess from the low-res pics of the programmer that i found so far …

Quote:
Originally Posted by bbbp View Post
The inverted servo is probably installed with the output shaft 180 degrees off compared to the other (both pointing out or both point in) so you get a "mirrored" effect.
No, i fear not. As explained above, i was talking in pulse uS all along, and not in direction. They do stop at different input signal ends, which is even stranger…

Thank so much yet again :-)
Regards
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Old May 12, 2015, 07:40 PM
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My hyperion dongle is identified by WinXP as a "Silicon Labs CP210x USB to UART Bridge"

It works with the free Graupner Servo software here:

http://www.graupner.de/en/newsdetail...5-f4331ec86b15

on Graupner and Airtronics equivalents of the DS09SCD but not with the Hyperion branded one. They need the Hyperion software.

BP
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Old May 12, 2015, 09:01 PM
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Calm down, why would you set center to be 15 mm down? What book told you to do that? ThY is such a meaningless set point. It sounds like if you had tested travel prior to epoxy you may have swapped left for right. But you should have also set the linkage based on Mon up travel you needed at max servo travel. And you should have done this test prior to epoxy. how did you epoxy them in.
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Old May 13, 2015, 03:51 AM
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Hi BP,

Quote:
Originally Posted by bbbp View Post
My hyperion dongle is identified by WinXP as a "Silicon Labs CP210x USB to UART Bridge"

It works with the free Graupner Servo software here:

http://www.graupner.de/en/newsdetail...5-f4331ec86b15

on Graupner and Airtronics equivalents of the DS09SCD but not with the Hyperion branded one. They need the Hyperion software.
That much i already know from various sites, but what would really help me are high-res photos of the PCB, if that’d be possible for you (or anyone here who has that programming device)! Although, if you don’t want to remove the covering from yours, i’d understand too .

Quote:
Originally Posted by elkski View Post
why would you set center to be 15 mm down? What book told you to do that? ThY is such a meaningless set point.
I’d do that because in the combination with this model, this servo (with the non-broken throws), this horn and this type/size surface-side horn, 15mm down when servo centered would mean that i get just the amount upward travel i need (plus a safety margin), and almost 90° down, just as i want. It’s just a value thats known from the last few models where this worked like a charm.

Thanks again!
Best Regards…
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Old May 13, 2015, 09:04 AM
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Shell, I'm glad you took my comments in a positive way. I feel we are on the edge of man and machine with the size and low cost of these servos and they almost need to be individually evaluated before installing them. I would however be upset if your not getting the servo spec range of arc with these servo's.
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Old May 14, 2015, 08:35 AM
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I will try to get a pic here soon. I have some lightweight shrink wrap to re-cover it.
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