Jermo's DX7 Setup Video

[Finless]

Gary because what the manual for the gyrop says is not correct.
50 on the gear channel is center stick so look at 50 as 0.
Anything above 50 is HH mode and anything below 50 is rate mode (normal mode).
Now because of the way JR works every step above 50 (or below) =1.44 in gain.
So in your case you have 74 for end point right?
74-50 = 24. Now 24x1.44 = 34.56 and rounded up that is 35.

Bob

[Jermo]

Gary I'm looking for KGFLY's post. Basically the answer is "because that's the way it works". Note in the example they cite specific radio's in use and even give two different examples. This supports KGFly's post that the DX7 is different.

As long as it works does it really matter why? I'll find the post.
Jermo

[Jermo]

Finless got it :)

here's why we thing this is true
Hmmm. I wonder if we are seeing a difference in the meaning of "100%" between radios, gyros and gyro-menu vs travel adjustment ?

Consider the following:

a) The universal servo control pulse is from 1ms to 2ms wide with 1.5ms being the centre command (0% position). Thus the full command range for a servo signal is 1ms or +/-0.5ms from the 1.5ms centre point.

b) For convenience computer radios have the concept of travel adjustment that goes beyond 100%, some go to 125% and some to 150%. How can this be if the servo range is 100% mechanical travel corresponding to a fixed command pulse range of +/-0.5ms from the centre ? The answer is that the meaning of 100% travel on each radio can be different.

From pg84 of the DX7 manual "The travel adjust range is from 0–150%.". This means they define +/-100% to mean +/-0.33ms with the extra 0.17ms providing the 50% overrange capacity.

Futaba is a bit different. From the 7c/9c manuals "Ranges from 0% (no servo movement at all) to 140%. At a 100% setting, the throw of the servo is approximately 40deg for channels 1-4 and approximately 55deg for channels 5-8."
Based on 140% corresponding to 0.5ms, their 100% must correspond to 0.36ms. However on the channel normally used for gyro control they say 100% corresponds to 55deg which means 0.46ms.

c) Now think about commanding the gyro range. We know that the gyro gain range control is split between HH and Rate around the 1.5ms midpoint. What we don't know is how Futaba define 100% gain. Is it 0.33ms offset, 0.4ms offset or 0.5ms offset ? My guess is that it is 0.46ms = 100% gain.

Now consider using simple endpoints on the JR/Spektrum gear channel. Since the logical endpoint of +/-100% is mapped to a physical endpoint of +/-0.33ms this corresponds .33/.46 = 72% with the gyro gain.

Now consider using the gyro menu. My theory is that 0 to 100% on the gyro menu corresponds to the standard -100% through +100% = 2 x 0.33 or 0.66ms range. So a 1% change in the gyro menu corresponds to 0.0066ms change in the command. If indeed the gyro defines 0.46ms as 100% then a 1% change in the gyro menu corresponds to (100* 0.0066)/0.46 = 1.44% change in gain.

Thus we can see (perhaps) how the 611 was reporting a 1.5% gain change for each 1% change in the DX7 gyro menu setting.

So if my analysis is correct (a big if!) my conclusions are:

Using a DX7 with a Futaba gyro (401 or 611):
a) Using the Gear channel endpoints is simpler to understand and gives enough operational range but due to the differences between JR/Spektrum and Futaba does not give a 1:1 mapping. Hence 100% Gear travel corresponds to 72% GY401/611 gain. Hence if you ever really wanted 100% gyro gain you would have set your endpoint to 139%.

b) Using the Gyro menu actual gyro gain is given by:

1.44 * abs(G-50) where G is the gyro menu value (0 to 100).

eg G = 30, Rate gain = 1.44 * 20 = 29%
eg G = 75, HH gain = 1.44 * 25 = 36%

---------------------------
Of course this is all speculation that would be easily cleared up with access to the equipment and an oscilloscope but I don't have either

[DavidH]

Just a suggestion. When using the GY 401 that you can not see what the actual gain setting is for the gyro.

Lower the ATV in both modes ( AVCS and Normal) till the gyro is just about not holding the tail. The gain sensitivity will be low. Then once you have done that, increase the sensitivity about 5 to 10 ATV points. This should allow the gyro to work well and hold the tail fine. This gyro will hold well with very little sensitivity. If the gain is too high, it is only overworking the tail servo and will cause it to fail prematurely. The GY gyros will usually not wag even with a very high gain sensitivity if the setup is correct. And when they do wag most don't recognize it as a wag because they can't usually see it happening. Usually the way to identify a wag with the GY gyros is by listening when the model is in flight.

David

[Finless]

Usually the way to identify a wag with the GY gyros is by listening when the model is in flight.


Yep especially when going backwards!!! On my 600 I didnt realize my gain was high until I started doing backwards stuff and heard the waggy sound! I wound up lowering it 4 more points!

David this is a good point... Many say to adjust gain until you get wag and then back off 3-4 clicks. Thats the way I been doing it until now as I am starting to do harder backwards stuff and noticed it still was too high. Not good for the servo thats for sure...

Bob

[Jermo]

Bob,
so far it seems we have three conditions:
1. Hunt - tail drifts/hops around in hover - remedy is more gain
2. Hold - tail holds
3. Wag - tail wags after a piro or turn due to gyro overcompensation - could be too much gain, too little resolution, governor use (no clue how this does it)..

sound right so far?
Jermo

[DavidH]

1. Hunt - tail drifts/hops around in hover - remedy is more gain
2. Hold - tail holds
3. Wag - tail wags after a piro or turn due to gyro overcompensation - could be too much gain, too little resolution, governor use (no clue how this does it)..



1. tail drifting/hopping around in a hover is not nessecarily caused by the gain being too low. It can also be caused by vibration to the gyro sensor. The GY gyros can hold very well at 25% -30% of actual gain sensitivity. So if it is drifting or hopping it is not always the gain setting. Linkage being tight, blade grips binding, and a couple other items can cause drifting.

3. Wag is usually caused by too much gain for the rpm of the tail rotor.
For example if the same gain setting is used at 1500 rpm on the main rotor and 2000 rpm. The tail is most likely going to wag at the 2000 rpm because the tail rotor is turning faster. That is why it is important to try and keep the rpms the same thru out the whole pitch range.
With the GY gyros the pop or wag that is seen after a piro is not usually from too much gain. The delay setting on the gyro can cure that problem most of the time.
The upper end radios have the delay function built into the radio programming.

Many say to adjust gain until you get wag and then back off 3-4 clicks

Bob,
Yes that use to be the way to do it with the mechanical gyros and then the first piezos. But the HH gyros hold really well. I have seen pilots losing servos with the GY gyros. And then when asked what there gain was set at. They have almost always replied they had it set very high. Once they lowered it down till where it would still hold and not overwork the servo they quit losing servos. Checking the servos with a temp gun after flights at different gain settings will show different temps on the tail servo. Heat is what kills the servos.

Gain settings also will depend on how the mechanical gain of the system is set up. There is a lot of newbies that don't realize the mechanical gain will affect how the setting of the electronic gain works.
I know a few pilots that run a low mechanical gain ( servo wheel ball closer to center). Then they can run a higher electronic gain without a problem.
David

[schniebw]

I'M CONFUSSED!!!
Too much info at once, brain overload, she's breaking up.

POWER DOWN!! POWER DOWN!!! POWER DOWN!!!!! :bawl :arggg:

Need caffine....... :shock: :WOW

[Jermo]

hehe..Schniebw, just watch The Finless Series video for the GY401, then watch my DX7 vid and it will all click. Most of the posts on this thread are just us digging out the details. All you really need is the results of our efforts which are all documented in the videos.

Jermo

[don_87]

Great video,
Thanks for taking the time to do this.

Don

[Jermo]

You are welcome. I'll be cleaning it up some in Revision 4 and adding a few more sections. Just letting this rev soak a bit to see if I get suggestions.
Jermo

[orlbuzz]

jermo,

I am relatively new to computer radios (used a JR 783 for sailplanes years ago), so I really appreciate your's and Finless' videos. I have set my BCPP up using them.

From what I have read, the exp. in the "curve" menus give a smoother curve, and in the "swash" menu, help to eliminate interaction in the collective/cyclic response. I would like to see that addressed in your future revisions.

Thank you again, for all your work.

orlbuzz

[Jermo]

will do sir :)
JErmo

[Jermo]

Revision 4 will be expanded to cover more features of the DX7.
The first part will be quick setup explaination specific to the T-Rex, the last part will be the features in more detail ordered by what I think is most used to the least used. I'm still writing the outlines for this revision. It may get pushed to rev5.

If anyone has suggestions/requests..etc let me know. I'm going to be re-doing some of the actual video footage and will be attempting to redo the audio tracks.
Jermo

[Fordpilot]

Thanks for videos. They are very helpful.

How about showing how to hook up DX7 to RF 3.5 sim.

[Jermo]

Thanks for videos. They are very helpful.

How about showing how to hook up DX7 to RF 3.5 sim.

I can do that if I get permission from HF staff to do it. Everything is pretty much on hold because I'was asked to stop. I was told that the information I was giving was wrong (I wasn't given any specifics or corrections).

There are a few posts in the G3.5 sim forum that explain how to set it up.
Jermo

[Finless]

Jermo... I would say go ahead and do it and ask the staff to review it. If it is correct there should be no problems.

Bob

[Jermo]

Jermo... I would say go ahead and do it and ask the staff to review it. If it is correct there should be no problems.

Bob

will do :) , I'll shoot it and send you a link like before. Thank you
Jermo

[R1Time]

Yes get this going, Im almost ready for my 450 maiden. I have the JR7202 and its going good so far with the video help Thanks!!!! :D

[sexytrexy]

[quote="mowery1"]Jermo, just watched your vid and was very helpful to a new guy like me who is just learning...Thank You!!... I'm looking forward to the next video....[/quote

After watching jermo's dx-7 video I fiinaly got my gy401 to work right I was not aware the transmiter had to be set on gear with gyro undernieth it to access the gyro sens option in the fuction's list. if you have it set wrong you wont even see this option. thaaaaaank you so much I can now fly my t-rex se with confidence.

[Jermo]

you're welcome ;)
Jermo

[REGULATER]

I would like to thank Finnless & jermo for the Vids and the time you have spent to help the noobes like me . I probley would have giving up on trying to set up my 450. There is no way i could have programed my DX7 with out your help.

[Jermo]

You're welcome, Bob(Finless) actually did all the work, I just adapted some of it to the DX7.
Jermo

[REGULATER]

Hi Jermo would you know what settings in the DX7 for the gain gyro for the 611
gyro 'Im setting up my 600 and not sure what the gain % to set it at . Is the same as the trex 450 on the 401gyro 72% ? Please let me know

Thank's Mark

[swasey1982]

cant see the video