SpartanRC DS760 Gyro Review and Setup Vids

[StatiC]

It will in a hover if you setup trim/subtrim so that the servo arm is 90 degrees at hover in rate mode. Which is the whole point of setting up the 90 degrees at the servo. This gives equal arc movement either direction from hover position.

[Finless]

Yes trimming in rate mode works but you must power up in rate mode then go to HH mode. If you power up in HH mode then HH mode will see the trimmed rudder as the NEW center stick position. Most people I know DON'T do it this way and correct me if I am wrong but most gyro need to be powered up in HH mode no?
If so (and I am unsure since I never tried this myself) then all this wonderful trimming you did in rate mode does nothing for HH mode.

Bob

[BruceW]

Originally Posted by Angelos

yes, but you will probably find out that as soon as you get back to HH mode the horn will no longer be at exact 90.

-Angelos

It seems the gyro makes a slight jump in position when switching between rate and HH mode and this was witnessed in both trimmed and non-trimmed configurations. Is the amount of this position change related to the difference in gyro endpoint limits? I guess this means my slider is probably not mechanically centered in the full range. Overall I will probably never come out of HH mode for all practical purposes.

[StatiC]

Whatever trim/subtrim you setup in rate mode will also be seen as 0 input signal from the transmitter if you power up in HH mode. You do not have to power up in rate mode with trim/subtrim added. I set all my helis up this way without issue.

The only exception to this rule is if you have not rebound your DX7 transmitter/rx to learn the new center position(with trim/subtrim). If the DX6/7 rx takes time to lock onto the tx signal then it will go to failsafe for the rudder which will be the last bound position. If you have applied subtrim/trim after binding your tx/rx and this happens, The gyro will see the bound position as 0 signal for rudder and then your rx will lock onto the tx and the tx will give the new trim/subtrim signal which is different and you will get drift.

I wonder if this gotcha causes some people trouble and makes them think trim/subtrim is bad.

As long as you rebind the DX6/DX7 tx/rx to the new fail safe tail servo center position after setting up rate mode for 90 degrees you won't have problems with trim/subtrim. Any time you change trim or subtrim though it is best to rebind the DX6/DX7 to program the new center signal(The manual states this too for this reason). As long as the rx/tx sync up before the fail safe position is given by the rx this issue will not reveal itself though.

Receivers that do not output any bound position at power on if the signal does not lock on does not have this problem (before 2.4ghz receivers?). I only have experience with the DX6 and DX7.

[StatiC]

Originally Posted by BruceW

It seems the gyro makes a slight jump in position when switching between rate and HH mode and this was witnessed in both trimmed and non-trimmed configurations. Is the amount of this position change related to the difference in gyro endpoint limits? I guess this means my slider is probably not mechanically centered in the full range. Overall I will probably never come out of HH mode for all practical purposes.

The reason it moved could be that in HH mode it is trying to correct for some amount of movement that it thought it saw so I wouldn't worry about it. Rate mode is the only easy way to know for sure if your servo is setup for 90 degrees on the arm at hover because it will auto center. In HH mode you would have to hover and look at the servo position. If you were to look at it in HH mode after landing or at first power on it could be anywhere in the travel trying to correct for some movement that it saw.

The important part for me is making sure at hover the servo is at 90 degrees for equal arc movement.

[BruceW]

I agree, setting it up for 90 in rate mode has worked just fine and once in HH mode, the gyro takes over anyway and locks in the tail. I'll be in HH mode the whole time anyway so this doesn't matter too much.

[Finless]

Yea this gets debated a LOT. I have seen more posts debating this "setup for rate" than I care to shake a stick at!

Believe it or not Pro's that I fly with dont do this!! They set up 90 and center the slider and be done with it!!!! I could name all kinds of well know names that do it this way. I know it's not right (per the manufacturers) but these guys dont ever use rate mode so it works for them and is easy to setup.

FYI other than my 6110T and this DS760 all my other gyros (401 and 611's) are setup 90 and center slider and I dont have a problem either. I did it that way because the Pro's I fly with said to do it that way right or wrong... It works for me.

So there you have it. Go figure aye?

Bob

[BruceW]

The difference here is that I'm not setting up for stable hover in rate mode, I'm only trying to get the servo arm to 90 and have the tail slider in the center mechanical position. What your talking about is different.

[Angelos]

This discussion has gone unnecessarily overcomplicated. The gyro does not care whether it is 90 degrees, 89 or 88. Keep it as close as you can and if you are picky use the the right servo arm or trim it any way you wish. But make sure the gyro is restarted to get the new mid-point for the AVCS mode. At the end of the day the gyro will work out what tail pitch is needed during flight even if the normal mode is a little out. The only reason for the 90deg is for the left and right arcs of the servo arm to be fairly symmetrical.

-Angelos

[Finless]

EXACTLY Angelos!!! That is what I have learned over the years too.... Your setup instructions about getting CLOSE with tail pitch worked perfect and is what I have really experienced on many other gyros too.... You really dont need to slice hairs to get a good working setup!

Bob

[StatiC]

Angelos, You just summed it up nicely.

Quick question for you... When setting up the limits does the tx signal at gyro power on determine the center position from where the limits are set? For an extreme case take that you give full subtrim one direction. Does the gyro use that power on signal to skew the center of the limit adjustment that direction? I wonder if this behavior is standardized by all the well known gyros out there.

[BruceW]

Thank you, that simplifies the discussion. The basic thing I wanted to know is whether the calculations being used by the firmware would be affected by trimming the servo to 90 and it sounds like they do not care. I want to stick with my non-90 Mikado servo arms so I will keep it setup the way I have already done with trimming and test fly soon.

[Angelos]

Originally Posted by xStatiCa2

For an extreme case take that you give full subtrim one direction. Does the gyro use that power on signal to skew the center of the limit adjustment that direction?

I guess you mean sub-trim on the radio. Let's ignore the gyro for a moment and assume that a servo is connected directly to the receiver which is a bit easier to understand (I connected my oscilloscope so I can get accurate measurements). On Futaba radios when the ATVs are at 100% and the stick at full travel the servo signal is only reaching 70% of it's potential full travel. Then the mid-point shifts because of trim or sub-trim the end-points also shift by the same amount. So the left and right controls remain symmetrical. However if you max-out the ATVs and then apply trim or sub-trim there will be no room for endpoint to move thus one side will get less travel. So if you are going to use lots of sub-trim and you want to keep both sides symmetrical you should not use max ATV; 5-8% less should be plenty. You should be able to see if it hits the end in the servo monitor screen. Most radios now have it.

-Angelos

[StatiC]

That helps a little but the main question I am trying to ask is not being communicated properly I guess. Let me try it another way. It can be difficult to describe things...

If I setup the gyro limits to not bind either direction with no subtrim/trim on the rx and then I go into the tx and give full subtrim and trim to the left will the gyro's idea of limit position change at next power on when the tx gives a new 0 input center signal position?

Now take that example and apply it to rate mode. Will the result be the same?

[Angelos]

No they won't change. The gyro limits as absolute. When the servo hits them it stops. No other setting will affect them either on the radio or the gyro itself. This applies to the ds760 and from observations I believe it applies to Futaba gyros too.

-Angelos

[Finless]

Hmmmm good question. I haven't tried this myself but as Angelos says most radios these days sub trim "slides" within the ATV's and thus as long as your ATV's are not maxed out you wont notice more throw in the trimmed direction.

Bottom line you can test this yourself with a servo alone. Set ATV's to 100/100 and then move the stick full left or right and measure the servos end throws. now TRIM or sub trim in either direction. Now move the stick full left and right again and you will see the same amount of throw. e.g. the trimming had no effect on the max deflection.
Now if you ATV's are maxed out (radio dependent) then you will see a difference.

Bob

[StatiC]

Thanks for the info. That clears that up that I have been going over in my mind but never tested for over a year now .

I am the type that has to understand how things work at the lowest level I can so I apologize if I am going too deep in the questions but I have another if you are up for the challenge of trying to understand my ramblings .

So when you set the limits on the gyro what servo output do you(as the gyro embedded programmer) use for the center point for the limit adjustment? In other words if you adjust the left and right limit all the way in on both left and right what would the center of those two servo signal outputs be? Arent all servos slightly different? Not that it really matters because you have separate limits for both sides and I am sure you have plenty of adjustment available to not be a problem if it is off from the real servo arm at 90 degrees.

I can see where having separate left and right limit adjustments might come in handy now. With a single limit adjustment if your servo when at 90 degrees on the arm is at a different position than what the center position of the limit adjustment is based off of then you will have less limit on one side than the other from your servo 90 degree angle center point.

Example for above with only one limit adjustment(gy401, G770 3D, etc):
limit adjustment center = x
limit adjustment end points based on center x above = y
Servo at 90 degrees at hover = o
|y---xo--y---|

Notice that the above example causes you to loose some movement to the right because the servo at 90 and the gyro limit signal center does not match.

Ideally I would have wanted it to be equal from the servo 90 degree center point:
|z---xo----z-|

The issues above is why I wondered if the gyro took the tx signal at power on to base the limit adjustment on.

Now how much this really is off might be so slight that it doesn't really matter normally for the gy401, G770 3D, etc. If you can not get the servo horn at a 90 degree angle without any trim/subtrim in rate mode though it could be off by quite a bit I would think(that is a different subject though). If it is off by a lot then having the separate limit adjustments would come in handy.

Any of this make sense?

[highland flyer]

I know this may seem a a dumb reply on what only amounts to a theory based answer.

In the radio you do not want any subtrim as the Gyro uses this as it's (stationary neutral point) otherwise it will creep.

Tail travel limit does vary in each direction as it is dependant on the particuliar models tail geometry and physicial tail slider travel limits, servo horn length/position.

Hover neutral position(The flight neutral point) can only be truly determined by flying in rate mode.

The tail travel limit is just that the physical amount of travel on the tail slider. The Gyro uses this to limit the slider travel in flight to prevent binding only. NOTE:-. It has NO effect on piro rate.
The tail travel limit % we actually see in the Gyro software is often an un-even figure each direction due to tail geometry of the model.

The Rudd ATV controls the piro speed only each direction

The idea of trimming the Gyro in rate mode is to find the approx hover pitch required to counter the main rotor torques. As far as I understand this, the gyro uses this as a reference point only, but the closer we can "Guess" this the less additionial calculations a Gyro has to do in flight. note:- the word Guess.

For example on the CSM720 this makes a huge difference to how well it can potentially perform and requires you to pre-set your talblade pitch in rate mode for best results. The CSM also has additional software programming to help teach the Gyro the tail blade position in flight (the flight neutral point). Even with this added programability it is still a compromise as the model will be moving, up/down/forwards /backwards/wind/ is headspeed dependant etc.

This setting is completely unique to each and every helicopter, as we use different, servo's, radio's, control rod settings, servo horn lengths and other things such headspeed, paddles/blade brand/length/ flybar length, tail blades size, gear ratio, air density, assymetric tail travel to help balance piro speed travel each direction. (with/against torque)

As Finless pointed out many of the 'Pro's' just stick it mid slider. Whist this works well for most Gyro's try this with a CSM and your results will be far from ideal.

The rest is in the Gyro designers head!

Sorry for the not so quick reply!

[StatiC]

I think an entire book could be written on 'R/C Helicopter Tail Control with Conventional gyros - Theory and Practical Use for the anally retentive builder' eal

Anyone want to help get a Creative Commons license book with that title going? .

[IcemanCharlie]

I just got my 760 and I tried it a little in my T-600 N.

I have used a 410 gyro before together with a S9254 Servo.

Now when I check my Low&High endpoints I can see that it's "rather" high, 128 and 143.

So if I understand this correct this is to high ( 90-110 in the manual) so I have to move the ball 1 or 2 steps further away on the servo arm.

This IS really a nice thing to see in the software!!

IF I would leave it as it is, would it be over sensitive or ?