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Old Aug 13, 2012, 10:22 AM
We can rebuild it!
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Enjoy! Oh and try get video!
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Old Aug 13, 2012, 01:55 PM
Safety : practice & promote!
RoboHeli's Avatar
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Here are some close-ups of the Twister's innards before and after I installed the Spektrum RX.

Before...

The 3-in-1 (ESC, mixer, gyro) module is the white box on the left and the 6-channel RX is the white box on the right. Note the very long wire that coils around in the lower part of the picture. That's the looooon drag-tenna.



Note that the helicopter comes with a 6 channel receiver even though it only uses 4 channels. I guess they just make a 6 channel one? The one thing that I had some problems with was figuring out the polarity of the servo wires at first (see below):



I know that the pins go SIGNAL, POWER, GROUND and that from the wire colors, I'd say that BLACK was ground and ORANGE was signal. Fortunately, I was right. Also, the AR400 had a little diagram that said which pin goes where. That was a nice little feature.

To bind the AR400, you insert the bind plug and then the only other connection I inserted was the throttle from the 3-in-1. The directions for the AR400 suggested that this was all you needed. Looks like they were right. The AR400 bound to my DX6i almost instantaneously as well. That was a pleasant surprise because sometimes I have to retry a couple of times to bind to the RX for my Blade micro helis and then it sometimes takes up to 30 seconds for those RXs to bind. Replacing the old RX was easy. I just clipped off the tie-wrap and then re-used the double-sided servo foam tape and attached the smaller AR400 RX to it.

After...

The AR400 is the little black box to the right of the white 3-in-1.



The AR400 has two antennas--a short one that's visible here (the little gray wire) and a longer one that I tie-wrapped to the central support beam. I'm not much of an antenna person so I have no idea whether that makes a difference or not. I've heard that carbon fiber can cause 2.4GHz signal loss or something which is why the bigger helis have satellite receivers (or so I think I've heard) but FWIW, I don't think I'll have problems with that with this helicopter.

I think I'll probably start with a 50% D/R with no expo. That's what works with my Walkera YS8001 and the 2403 TX that I use with it (Obligatory shout out : thanks again, E2, for the 2403!)
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Old Aug 13, 2012, 08:16 PM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
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Originally Posted by RoboHeli View Post
Uh oh. Now I've done it. I found a "never flown" RTF 72MHz Twister Skylift on ebay last week and won it.
.
Congratulations Robo!! (and thanks for the shoutout ... ...)
... oh, and BTW, I have a never FLOWN Skylift also (as it crashed into a table and got totalled 20sec into the maiden flight ... and has never been touched since ...)

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Old Aug 13, 2012, 09:01 PM
Safety : practice & promote!
RoboHeli's Avatar
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Update : I have no rudder control. I'm not sure what's going on.


I connected everything properly (there's only 4 channels!) I verified I had throttle and I verified I had elevator and aileron control. However, when I took off, the heli spun uncontrollably. Not unlike what it might look like if I was giving it max right rudder (I think it was right rudder...as I *think* it was spinning CW but now I can't remember...)

So I took the blades & flybar off, took the canopy off, and took a good look at how I had everything plugged in. It all looked good. When I spun it up on the bench, if I gave it rudder commands, I would hear NO audible change in motor speeds as you would expect if you were yawing with a coaxial.

Thinking that maybe my rudder channel was dead, I disconnected everything from the RX except for the throttle, plugged the aileron servo into the rudder channel and powered it up. That worked. If I gave it rudder commands, the aileron servo moved. Okay, so my rudder channel in the Spektrum RX worked.

So then I disconnected the Spektrum RX and reconnected the 72MHz RX. Okay, well, when I do THAT, I get clear indication that rudder signals are being acted up. I can spool up the motors and I can hear the motors changing pitch as I move the rudder back and forth (yes, I'm making sure to keep the throttle at the same position).

Maybe the analog receiver is sending a different kind of command to the rudder??? Well, to test that, I plugged the aileron servo into the 72MHz RX rudder. That worked. I could control the servo EXACTLY THE SAME WAY as I could do it with the Spektrum 2.4GHz RX in the paragraphs above.

What???

For some reason, the 3-in-1 is not responding to the rudder channel from the 2.4GHz Spektrum RX but the servos, if plugged into them, do respond just fine. However, the 3-in-1 responds just fine if I use the 72MHz RX to give it rudder commands.


Okay, the ONLY thing that I could think is potentially different here is HOW the RX is outputting the signals. Maybe the Spektrum RX is outputting its signal in a different fashion than what the 3-in-1 is expecting? I guess the only way I could tell for sure is if I put it on an oscilloscope or something.

This helicopter uses a 3cell LiPo. Does that matter? Would the AR400 not work correctly with a 3cell LiPo? Or does that not matter? I wonder if a 6-channel Spektrum RX would somehow work differently? There's precious little documentation on what exactly the 3-in-1 outputs in terms of voltage (need to measure...) nor what the AR400 needs or can correctly operate on.


Hmmmm.... anybody have any thoughts? I'm kind of stymied here.
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Old Aug 13, 2012, 09:47 PM
"whirlydude"
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Roboheli, is your dx6i setup with the aileron, elevator, and rudder channels reversed as it states to do with the cx2 helicopters? If so, try switching the rudder back to normal, and rebind. I don't know if that will change things, but it may be worth a try.
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Old Aug 13, 2012, 09:59 PM
Safety : practice & promote!
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Originally Posted by flyeraroo View Post
Roboheli, is your dx6i setup with the aileron, elevator, and rudder channels reversed as it states to do with the cx2 helicopters? If so, try switching the rudder back to normal, and rebind. I don't know if that will change things, but it may be worth a try.
Thanks, but no, rebinding with rudder channel normal or reversed didn't work in either case.

I dug out my old oscilloscope (an ancient analog HP 1217A) and I looked at the signal coming from the rudder pins on both the Spektrum 2.4GHz RX and the Twister 72MHz RX. After a lot of fiddling around and trying to remember how this thing worked, I finally got it to the point that I was outputting a trace. However, for the life of me, I couldn't see a difference between the 2.4GHz servo output and the 72MHz servo output. The voltage appeared to be the same and the pulse width appeared to be roughly the same as well.

About the only thing I can think is that the 3-in-1 is doing something odd when it comes time for initialization and the 72MHz RX outputs something differently somehow that my otherwise limited skills with the o-scope just can't pick out.

Grrr....I may need to try a different RX. Maybe I can find an old AR6100 like was reported in the article I cited earlier. Maybe the DSM2 does something slightly differently than the DSMX? Arrrgh. This is frustrating.
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Old Aug 13, 2012, 11:33 PM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
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Originally Posted by RoboHeli View Post
Update : I have no rudder control. I'm not sure what's going on.


I connected everything properly (there's only 4 channels!) I verified I had throttle and I verified I had elevator and aileron control. However, when I took off, the heli spun uncontrollably. Not unlike what it might look like if I was giving it max right rudder (I think it was right rudder...as I *think* it was spinning CW but now I can't remember...)

So I took the blades & flybar off, took the canopy off, and took a good look at how I had everything plugged in. It all looked good. When I spun it up on the bench, if I gave it rudder commands, I would hear NO audible change in motor speeds as you would expect if you were yawing with a coaxial.

Thinking that maybe my rudder channel was dead, I disconnected everything from the RX except for the throttle, plugged the aileron servo into the rudder channel and powered it up. That worked. If I gave it rudder commands, the aileron servo moved. Okay, so my rudder channel in the Spektrum RX worked.

So then I disconnected the Spektrum RX and reconnected the 72MHz RX. Okay, well, when I do THAT, I get clear indication that rudder signals are being acted up. I can spool up the motors and I can hear the motors changing pitch as I move the rudder back and forth (yes, I'm making sure to keep the throttle at the same position).

Maybe the analog receiver is sending a different kind of command to the rudder??? Well, to test that, I plugged the aileron servo into the 72MHz RX rudder. That worked. I could control the servo EXACTLY THE SAME WAY as I could do it with the Spektrum 2.4GHz RX in the paragraphs above.

What???

For some reason, the 3-in-1 is not responding to the rudder channel from the 2.4GHz Spektrum RX but the servos, if plugged into them, do respond just fine. However, the 3-in-1 responds just fine if I use the 72MHz RX to give it rudder commands.


Okay, the ONLY thing that I could think is potentially different here is HOW the RX is outputting the signals. Maybe the Spektrum RX is outputting its signal in a different fashion than what the 3-in-1 is expecting? I guess the only way I could tell for sure is if I put it on an oscilloscope or something.

This helicopter uses a 3cell LiPo. Does that matter? Would the AR400 not work correctly with a 3cell LiPo? Or does that not matter? I wonder if a 6-channel Spektrum RX would somehow work differently? There's precious little documentation on what exactly the 3-in-1 outputs in terms of voltage (need to measure...) nor what the AR400 needs or can correctly operate on.


Hmmmm.... anybody have any thoughts? I'm kind of stymied here.
are the channels in the exact same order ?? like the thing with esky being aile1, elev2, thro3 and rudd4 vs. blade being thro1, aile2, elev3 and rudd4 (if i remember this right ...) ??
because if this is the case, then it would be (one should expect) exactly as it is with flying a bol with a spektrum rx - if you just plug the respective channel in the respective slot on the RX, it wont work ... the channels have to be in the right order ... (but this is only a shot from the hip and I am not going to dig mz twister out to look it up, sorry ... ...)
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Old Aug 13, 2012, 11:34 PM
"whirlydude"
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Originally Posted by RoboHeli View Post
Thanks, but no, rebinding with rudder channel normal or reversed didn't work in either case.

I dug out my old oscilloscope (an ancient analog HP 1217A) and I looked at the signal coming from the rudder pins on both the Spektrum 2.4GHz RX and the Twister 72MHz RX. After a lot of fiddling around and trying to remember how this thing worked, I finally got it to the point that I was outputting a trace. However, for the life of me, I couldn't see a difference between the 2.4GHz servo output and the 72MHz servo output. The voltage appeared to be the same and the pulse width appeared to be roughly the same as well.

About the only thing I can think is that the 3-in-1 is doing something odd when it comes time for initialization and the 72MHz RX outputs something differently somehow that my otherwise limited skills with the o-scope just can't pick out.

Grrr....I may need to try a different RX. Maybe I can find an old AR6100 like was reported in the article I cited earlier. Maybe the DSM2 does something slightly differently than the DSMX? Arrrgh. This is frustrating.
Yeah, it seems the 3 in 1 is not communicating with the rx. The rx and tx are bound, because the servos are working, but the throttle and rudder coming from the 3 in 1 are not. That is why your heli spooled up spinning wildly when plugging in the battery. It was not seeing your tx, just going from esc to motors, so you have no mixer or gyro, controlling the helicopter. I don't think a 6 channel rx will make much of a difference. It could be because the rx is DSMX rather than DSM2, but I'm not sure. I don't know if the 3 in 1 has something to do with MHz, and that's why is not communicating with the 2.4 GHz?
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Old Aug 13, 2012, 11:36 PM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
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Originally Posted by flyeraroo View Post
Yeah, it seems the 3 in 1 is not communicating with the rx. The rx and tx are bound, because the servos are working, but the throttle and rudder coming from the 3 in 1 are not. That is why your heli spooled up spinning wildly when plugging in the battery. It was not seeing your tx, just going from esc to motors, so you have no mixer or gyro, controlling the helicopter. I don't think a 6 channel rx will make much of a difference. It could be because the rx is DSMX rather than DSM2, but I'm not sure. I don't know if the 3 in 1 has something to do with MHz, and that's why is not communicating with the 2.4 GHz?
I have really not followed this at all, but shouldnt dsmx be "downward-compatible"??
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Old Aug 13, 2012, 11:42 PM
"whirlydude"
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Originally Posted by erdnuckel2 View Post
I have really not followed this at all, but shouldnt dsmx be "downward-compatible"??
Yeah, that is my impression, it suppose to be I thought. I'm thinking there is something to do with the frequencies, and that is why it's not communicating. I wonder if the guy that had done this is still around?
edit: I guess if nothing else he could use a EFLH1023, and go with a 2s battery.
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Old Aug 13, 2012, 11:57 PM
Safety : practice & promote!
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Originally Posted by flyeraroo View Post
Yeah, it seems the 3 in 1 is not communicating with the rx. The rx and tx are bound, because the servos are working, but the throttle and rudder coming from the 3 in 1 are not. That is why your heli spooled up spinning wildly when plugging in the battery. It was not seeing your tx, just going from esc to motors, so you have no mixer or gyro, controlling the helicopter. I don't think a 6 channel rx will make much of a difference. It could be because the rx is DSMX rather than DSM2, but I'm not sure. I don't know if the 3 in 1 has something to do with MHz, and that's why is not communicating with the 2.4 GHz?
No, the throttle appears to work just fine. I can spin up the motors and slow them down with the throttle control with no problems.

The only thing that doesn't seem to be working is the Twister 3-in-1 reading a servo pulse signal from the Spektrum on the input to the rudder. Like I said, the throttle input to the 3-in-1 works fine. I can slowly spool up the rotors but since the rudder seems to be wonky, the heli seems to think I'm telling it to piro. Once I slow the throttle down and land, friction takes over and the blades spin at a reasonable slow rate until I zero the throttle.

The only reason I mention the DSM2 6-channel module is because the link that I posted originally had a use-case where a guy who had a 33MHz analog twister successfully used the 6100 electronics. My working hypothesis is that there's something wonky about the AR400 RX (maybe it doesn't supply adequate *current* to the servo output signal???) which may work properly on the AR6100.

The fact that one is DSMX and the other is DSM2 doesn't matter in this hypothesis. Neither does the fact that one is 4ch vs. 6 ch. per se. I'm just speculating wildly here, but it might be that the AR6100 just has beefier output signals because it's supposed to be sourcing more current with 6 servos???

I might just order one and see what happens. Even if it doesn't ultimately work, having a working 6-channel Spektrum RX can be useful for other projects.
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Old Aug 13, 2012, 11:58 PM
Safety : practice & promote!
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Originally Posted by flyeraroo View Post
Yeah, that is my impression, it suppose to be I thought. I'm thinking there is something to do with the frequencies, and that is why it's not communicating. I wonder if the guy that had done this is still around?
edit: I guess if nothing else he could use a EFLH1023, and go with a 2s battery.
What capacity 2s battery did you end up using? The 3s twister battery is a 800mah capacity.
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Old Aug 14, 2012, 12:13 AM
It flies!!! ... so who cares ?
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this is the last thing I do before goto sleep!!! ...
I just checked the txs, the aile1, ele2, thro3 and rudd4 is the same order as with esky!!! so the solution is in the last few pages of the BOL thread!!
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Old Aug 14, 2012, 10:18 AM
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E2, I have no idea what you're talking about.

Why are you going on about Esky? Is the Twister an Esky-brand model? (As in Esky the makers of the Big Lama and Honey Bee?)

What is BOL? E2, this is very cryptic and I'm completely lost here in what you're saying.



So, here's where you guys are losing me. Why are you going on about the ordering of the channels? Check out the wiring diagram that flyeraroo was kind enough to send me (I hope I'm not violating anything by posting it--if so, please tell me and I'll remove it)



Why should it matter what channels are transmitted in what order? Once they go to the RX, the RX separates them and converts them into servo pulses that go to the individual servos. I've already verified that all four channels are properly being transmitted and received by my Spektrum RX. The problem seems to be that the 3-in-1 doesn't like how the rudder signal is coming into it fromt he Spektrum RX.

Now...this talk about the ordering of the channels has now got me thinking about timing. Maybe this is what you guys were talking about and I was just missing it??? Maybe the *timing* of when the throttle and rudder pulses come in matters? That is, what if the throttle pulse is meant to be received just BEFORE the rudder pulse (or vice versa)? Maybe the Twister 72MHz RX sends the throttle & rudder pulses in the correct order but the Spektrum RX reverses them? Then the 3-in-1 gets confused and thinks that the I'm sending either a maximum or minimum length rudder signal?

I went ahead and placed an order for a Spektrum AR6100 RX this morning since that was the one that was reported to work on that web page I found. If it doesn't, then well, I'll have a spare RX for another project someday. But here's hoping!


(E2, I still want to follow up with what you're saying...can you elaborate?)
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Old Aug 14, 2012, 04:57 PM
It flies!!! ... so who cares ?
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Hey Robo,

BOL is the acronym for the Esky Big Outdoor Lama, but I can see from the picture, that the Twister has the same channel order as a CX2.
So my suspicion would be, that the time between the pulses on a DSMX RX is shorter than on the DSM2 RX ... and for that reason it confuses the 3in1. I also read on the german forum that it MAKES a difference if the pulses come with a gap like ch1 thro - ch4 rudd vs. right in sequence like ch3 thro - ch4 rudd ...

Furthermore, there someone wrote that with a DX7 it would work better than with a DX6i (just for a different heli ...)
so there are a lot of "mysteries" to be resolved ...
(I am sure you will get this "sorted out ..." sooner or later ... (theres a lot of people who could throw ideas around ...)

Hope this helps a littlle

E2
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