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Old 01-31-2013, 04:41 AM   #1
mclarkson
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Default Spektrum Mixing / Programming ... ARGH!!!

I've started threads in the past, here and elsewhere, hoping to find someone who can explain the vagaries of Spektrum programming. These usually elicit several responses of, "I'd like to know that too!"

Followed by a few pointers to example set-ups which may work but never explain why / how they work.

Followed by silence.

Followed by me giving up.

Can it really be this hard?

Example from tonite. I need to use my AUX2 switch on the DX7 Tx to drive the gear channel. For whatever reasons, I need the switch to move the gear channel from -50% to +50%.

I try a setup. It doesn't quite work. But when I go back to programming, the Tx will no longer let me edit some values. I can edit them when I first create the mix, but never afterwards.

Let's say I start on MIX 1 with:
RATE: 50%
50%
OFFSET: -100

Let's say that doesn't work. I want to change the rates to 75% and 75%. Guess what? I can't.

When setting up the mix for the first time, I can flip the AUX2 switch up and down to switch between the two RATE settings in the mix. But, once I've set it up and tested it, flipping the switch does nothing. At all. I can never, ever get to the second rate setting.
RATE: 50%
(UNCHANGEABLE) 50%
OFFSET: -100


I have to start a new mix (MIX 2). When I set up this mix, I can flip the AUX2 switch up and down to enter values for the two rates but again, once I move off the Mix programming screen, I can never ever alter the second rate again.

So I have to start a new mix (MIX 3).

Etc.

Etc.

Until I'm out of mixes. If I go back to an old mix (eg MIX 1) I have to individually clear out ALL of the settings before it will let me alter the second rate again.

Am I missing something? Cuz I'm really frustrated.

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Old 01-31-2013, 05:31 AM   #2
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Originally Posted by mclarkson View Post
I've started threads in the past, here and elsewhere, hoping to find someone who can explain the vagaries of Spektrum programming. These usually elicit several responses of, "I'd like to know that too!"

Followed by a few pointers to example set-ups which may work but never explain why / how they work.

Followed by silence.

Followed by me giving up.

Can it really be this hard?

Example from tonite. I need to use my AUX2 switch on the DX7 Tx to drive the gear channel. For whatever reasons, I need the switch to move the gear channel from -50% to +50%.

I try a setup. It doesn't quite work. But when I go back to programming, the Tx will no longer let me edit some values. I can edit them when I first create the mix, but never afterwards.

Let's say I start on MIX 1 with:
RATE: 50%
50%
OFFSET: -100

Let's say that doesn't work. I want to change the rates to 75% and 75%. Guess what? I can't.

When setting up the mix for the first time, I can flip the AUX2 switch up and down to switch between the two RATE settings in the mix. But, once I've set it up and tested it, flipping the switch does nothing. At all. I can never, ever get to the second rate setting.
RATE: 50%
(UNCHANGEABLE) 50%
OFFSET: -100


I have to start a new mix (MIX 2). When I set up this mix, I can flip the AUX2 switch up and down to enter values for the two rates but again, once I move off the Mix programming screen, I can never ever alter the second rate again.

So I have to start a new mix (MIX 3).

Etc.

Etc.

Until I'm out of mixes. If I go back to an old mix (eg MIX 1) I have to individually clear out ALL of the settings before it will let me alter the second rate again.

Am I missing something? Cuz I'm really frustrated.
Out of curiosity, why are you not using the original gear switch??

A while back, I was using the gear switch with a mix for a throttle cut off switch. Found how on the Internet, worked out very well.

I did find out though that Mix 1 did not work, and Mix 2 did work. Got some suspicions that the DX7 mixes only work with specific switches. Might be wrong, but the Mix 2 did work, Mix 1 with exactly same settings did not.

Now have the DX8, and this transmitter is several orders of magnitude easier to program complex settings than my DX7.

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Old 01-31-2013, 02:45 PM   #3
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Mark,

I have a DX7 as well. I am not an expert on programming it, but I have noticed that the parameters you are looking at are only available to edit when you have that channel past the midpoint moving in that direction.

For example, if you are mixing the xx output to be controlled by the elevator input control, you need to move the elevator control up to change one % and down to change the other. In your case, you may need to temporarily change the offset so you can get to the other end % setting. Also, mixing your gear input switch to an unused output may help as well. Things get weird when two inputs goto one output.

In general, the offset has always bit me, until playing for a while.

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Old 01-31-2013, 08:53 PM   #4
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No one has ever been able to explain offset to me in a way that could penetrate my skull.

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Old 01-31-2013, 09:05 PM   #5
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Right from the DX7 manual:

The purpose of the mixing offset is to redefine the neutral position of the slave channel.
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Old 01-31-2013, 09:32 PM   #6
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Originally Posted by Stevephoon View Post
Mark,

I have a DX7 as well. I am not an expert on programming it, but I have noticed that the parameters you are looking at are only available to edit when you have that channel past the midpoint moving in that direction.

For example, if you are mixing the xx output to be controlled by the elevator input control, you need to move the elevator control up to change one % and down to change the other. In your case, you may need to temporarily change the offset so you can get to the other end % setting. Also, mixing your gear input switch to an unused output may help as well. Things get weird when two inputs goto one output.

In general, the offset has always bit me, until playing for a while.

Steve
I think Steve nailed it. The -100% offset means that the aux switch can never drive the slave channel past the mid point, so flicking the switch cant activate the other 'half' of the mix.
I think it will work if you put the offset to zero, make, the adjustments as you want (flicking the switch as required) then put the offset back to -100.
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Old 01-31-2013, 11:01 PM   #7
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Thanks, I'll play with that.

Originally Posted by Turner View Post
Right from the DX7 manual:

The purpose of the mixing offset is to redefine the neutral position of the slave channel.
I know. It sounds so simple and straightforward in the manual but when I try to do something with it, my brain starts to bleed. I spent a week last year working on a throttle kill switch. I eventually found settings that work (for some ESCs) but I could never understand exactly how/why they were working.

If I set my RATE to 50% and my OFFSET to 50, my output goes from 12.5 to 112.5.

If I set my RATE to 50% and my OFFSET to -50, my output goes from 37.5 to 137.5.

If I set my RATE to 100% and my OFFSET to 50, my output goes from 25 to 125.

If I set my RATE to 100% and my OFFSET to 100, my output is unchanged: 0-100.

If I set my RATE to -100% and my OFFSET to 50, my output goes from -25 to 75.

If I set my RATE to 100% and my OFFSET to 0, my output goes from 50 to 150.

*splodes*

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Old 02-01-2013, 02:19 AM   #8
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If you haven't already, can you say what you are trying to accomplish.
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Old 02-01-2013, 02:44 AM   #9
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Originally Posted by mclarkson View Post
I spent a week last year working on a throttle kill switch.
I found this throttle kill switch for the Spektrum DX7 (Not tried on the DX7i) on the Internet. It worked well on both of my DX7 transmitters. FYI, doing a throttle kill switch on my Spektrum DX8 is a simple 10 second job.


Electric Flight Safety
Ideally every electric aircraft you have should be equipped with an arming device on the craft itself (either and ESC switch or power interrupter plug) as well as having a throttle cut switch on your transmitter. Since electric motors can startup unexpectedly and inflict a lot of painful damage the double precaution can avoid some nasty injuries. Although an arming switch/plug on the aircraft ought to be sufficient on its own there are times when it is armed with the intention of flying but something distracts you and the aircraft is now vulnerable to a careless jog of the throttle lever, the transmitter becomes your last line of defense.
I have implemented a transmitter disable switch for all my aircraft (helis as well as conventional planes) this way the process is second nature to me. The idea is that whenever the aircraft is not expected to fly the transmitter switch is in the disable position. The moment before takeoff I switch it to enable, fly as required then the moment the aircraft touches down and I have completed taxiing it I always click the switch to disabled.
Some of the more advanced transmitters have the ability to set a throttle cut switch up within their menus however others need a little work to make it happen. Below I give the process needed to set up a Spektrum DX7, it is likely this technique can be used on other transmitters, it is well worth doing and if you are still unsure how try looking online for your particular transmitter.
In my case I use the switch at the top right hand corner of the transmitter as the kill switch, this seems to be a standard as far as I can tell, the DX7 does have a label saying HOLD for this switch (as well as Ruder D/R).

Setup Process For the Spektrum DX7 Transmitter:
From your selected plane setup menu (pressing scroll and select simultaneously) move to one of the mixing channels (Kyleservicetech used Mix 3, for mixing with the gear switch).
Select source and destination for the mix to be THRO (short for throttle), the display should show:
THRO -> THRO
Now move to the rate section and set both sections to -100% (you will be able to set one of them with the throttle stick down and the other with it up).
Move to the SW: section and set it to MIX
Move to the OFFSET section and set it to -100%.
If you toggle the gear switch you should see the text to the right of the THRO -> THRO change from OFF to ON, when this reads ON the throttle is disabled (this should be with the switch pulled toward you).

[PROG.MIX1]
THRO->THRO ON
RATE: -100%
-100%
>SW:MIX
OFFSET:-100
Carefully try this out with your model turned on, with the switch toward you it should not be possible to start the motor at all (even helis should be disabled despite the position of the idle up switch). And, as always, check all remaining transmitter functions for both direction and unexpected operations. In case something else got changed by accident.
All that remains now is to cultivate the habit of ensuring the switch is in the disabled position whenever you pick up the aircraft and whenever it is not on the flying field.

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Old 02-01-2013, 03:07 AM   #10
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found this the other day trying to do flaperons...
throttle kill bout 2/3's down the page..

http://www.rc-soar.com/spektrum/index.htm

all kinds of answers/questions here...per one of the best reviews on the dx7

http://www.rcgroups.com/forums/showthread.php?t=583877

cr
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Old 02-01-2013, 08:46 PM   #11
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Here is an interesting thread from RCG. Look at post no. 2. I can't make sense of the top party but the bottom shows the effect of offset.

http://www.rcgroups.com/forums/showthread.php?t=1196740
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Old 02-01-2013, 11:42 PM   #12
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Originally Posted by Turner View Post
If you haven't already, can you say what you are trying to accomplish.
Turner, what I'm mainly trying to accomplish is getting my head around how offset and rate actually work. The problem with a particular task (eg throttle kill switch) is I can find setups on the int0rwebs that work, but I never understand them.

Offset, for example, seems simple. It moves the center point of the mix, right? So an offset of 50 should move the center point of the mix from 0 to 50, right? Instead of running from -100 to +100, my mix output should run from -50 to +150. That's what I would expect.

But, with RATE at 100%, an offset of 50 moves the center point of the mix up 25, not 50. So now it runs from -75 to 125.

How about an offset of -50? Again, I'd expect the output range to run from -150 to 50, shifting the center of the mix down by 50. But no. Now the output range (at 100% rate) runs from -25 to 175.

I recently built a mix for my gear channel. I wanted it to run from -50 to 50, instead of from 100 to 100. The answer was to set the ON rate to -50 and also set the OFF rate to -50. (Offset = 0).



I clearly do not understand what is going on here.

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Old 02-02-2013, 01:09 AM   #13
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I wish I had a good answer for you. it's been several months since I played with mixes. Learning Heli setup at the moment. I have a renewed interest in now and will study on it.
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Old 02-05-2013, 07:45 PM   #14
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Default Mixes, Rates, and Offsets

I haven't forgotten about this, Mark. I've been working on it when I can. The stupid, irritating beeper makes it impossible when my wife is around. I wish there was an easy way to defeat that thing at will.

I've made some headway but have confused myself at times as well. Need to start making detailed notes of each setting and result.

One important thing to understand, with the DX7, is that all servo movement directed away from center stick is positive. As this applies to the Travel Adjust screen, you will note that all the default settings are 100%. That is positive 100%. This applies to throttle as well. Throttle low stick is 100% positive movement down and away from 0% center stick. Throttle high stick is 100% positive movement up and away from 0% center stick.

On the travel Adjust screen, left of the rates are:

H/L - Throttle
L/R - Aileron
D/U - Elevator
L/R - Rudder
U/D - Flap

For Gear and Aux 2 it changes to + and − and I think this adds to the confusion. The values are still positive. Need convincing? Alter the − value for Gear and/or Aux 2 and see what happens. If it was negative 100%, pushing increase would start counting down from 100% to 99 etc. But in doesn't work that way. Increasing counts up, decreasing counts down. The value is positive with a range from 0% to 150% and the default at 100%.

Note that the graduations on the Servo Monitor screen are 50%, 100%, and 150% to left and right of 0% center. Again think of these as positive values in both directions. With the Mix rates set at +125%(maximum) the resulting slave channel servo movement is 125% of the master. With rates set at 50% we get servo movement of 50%. Rates at 0% we get 0 servo movement, etc. If we go to negative rates we change the servo direction to the opposite side of center with the servo movement still matching the actual rate number. That's important, negative Mix rates change servo direction. Try it and verify on the Servo Monitor screen.

I opened a new model memory to set up different mixes. With everything at the default settings you get Wing Type off, off, off, or normal wing W/one aileron servo. Travel Adjust is also at default 100% for all channels. Travel Adjust range is from 0% to 150% for all seven channels in each direction.

Mark, this first part relates to your post #12.

Set up a thro > thro mix. Zero rates, no effect. Now add a −50% rate on the high end. This allows normal throttle to the mid stick position and reduces servo/throttle travel by 50% from mid to full stick with linear response. If we could see this as a throttle curve we would see a straight line at 45˚ from low to mid stick and then a straight line from mid to full stick but at a 22.5˚ angle. Now add +100 offset. Full normal linear throttle range is restored. Now change offset to −100 and we get a linear response over the full stick range but the output/travel is from zero to mid throttle. A 100 point offset offsets 100% of the change induced by the negative rate.

Next I tried a +50% rate again on the high side. Low to mid stick is normal, mid to high stick overdrives the servo/throttle to 150%. Like the example above, the response is linear from low to mid and from mid to high but if we could see the curve, low to mid would be at 45˚ and mid to high would be at a different angle. Following the first example I added a +100 offset and as before full normal linear throttle range is restored. A −100 offset drives servo/throttle travel off the screen to 200% I presume. So, as in the first example a 100 point offset offsets 100% of the change induced by the rate.

Next I want to compare this to a mix of one channel to another and look at the throttle cut mixes. I hope this isn't so basic as to seem unnecessary but since Spektrum has never spelled it out for us I feel it's starting point for me to understanding rates and offsets. The DX7 is my first and only computer radio and probably my only for quite some time. I really want to get to understand it as much as I can.
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Old 02-05-2013, 08:48 PM   #15
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Thanks. I'll try to digest that and come back with more questions.

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Old 02-05-2013, 09:44 PM   #16
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I don't understand why an OFFSET of 100 seems to nullify the mix altogether, regardless of rate settings.

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Old 02-05-2013, 11:17 PM   #17
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I don't know if you have done any heli throttle curves. The DX7 has a 5 point throttle curve. The five points are 0%, 25%, 50%, 75%, 100%. These represent throttle stick position. But in terms of servo travel it's actually 100%, 50%, 0%, 50%, 100%. Both sides of 0% are positive values but one side is left and the other right.

Try this:

thro > thro - both rates at −50% - What you see on the servo monitor screen is a range from 50% left of center to 50% right of center. But in terms of throttle position it is 25% throttle to 75% throttle.

Enter −100 offset - This offsets all points on the curve 50 points to the left or 100% of the 50 point change induced by the rate.

Enter −50 offset - This offsets all points on the curve 25 points to the left (of where they were with zero offset) or 50% of the 50 point change induced by the rate.

I need to run some other numbers to be convinced that this is right but the numbers add up and at this point I think this is what's going on so I'll throw it out there for you to look at and work with. Still a lot more to do to understand all this.

I reserve the right to revise and amend all of this. My head hurts.
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Old 02-06-2013, 06:44 AM   #18
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Originally Posted by mclarkson View Post
I don't understand why an OFFSET of 100 seems to nullify the mix altogether, regardless of rate settings.
It doesn't. it just offsets the centre point. For instance if you added -100 offset on a mix to throttle that would make the mid throttle stick position equal to closed throttle. The actual mixes would still work though obviously on the negative side of the travel there would be no effect because the throttle is already closed.
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Old 02-06-2013, 07:44 AM   #19
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I really appreciate both your help and your delightful accent.

Let me give you an example of why I'm confused about OFFSET.

Say I want a throttle kill switch. I'll put it on my AUX2 switch and make this mix:
AUX2->THRO
RATE: -125% / 0%
SW: ON
OFFSET: -100

When I throw AUX2, it pushes throttle output below 0. When I flip it back, it does nothing; the throttle acts as before. Well and good.

But if I do the same mix with a positive OFFSET, it does nothing at all.
AUX2->THRO
RATE: -125% / 0%
SW: ON
OFFSET: 100

Throttle works normally no matter which way the switch goes. But suppose I change the RATE to a positive amount, like +125%? Or +100%? Or +50%? Or +67%?

AUX2->THRO
RATE: +67% / 0%
SW: ON
OFFSET: 100

It doesn't matter. As long as OFFSET is 100, nothing whatsoever happens. The throttle works normally.


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Old 02-06-2013, 07:03 PM   #20
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Originally Posted by mclarkson View Post
I really appreciate both your help and your delightful accent.

Let me give you an example of why I'm confused about OFFSET.

Say I want a throttle kill switch. I'll put it on my AUX2 switch and make this mix:
AUX2->THRO
RATE: -125% / 0%
SW: ON
OFFSET: -100

When I throw AUX2, it pushes throttle output below 0. When I flip it back, it does nothing; the throttle acts as before. Well and good.

But if I do the same mix with a positive OFFSET, it does nothing at all.
AUX2->THRO
RATE: -125% / 0%
SW: ON
OFFSET: 100....
Your −125% rate is being neutralized by the 100% positive offset. A positive offset undoes the effects of a negative rate. Gradually change from the −100 offset and watch the effect. When you get to Zero offset you will see that the effect of the negative rate in this AUX2 > THRO mix is more like an offset. The −125% rate has offset the throttle range 125 points to the left. As you continue towards 100 offset the negative rate is eventually offset by 100%.

If you mix 2 stick channels, say rudder to elevator, when you input a negative rate it reverses servo direction. With this particular mix it could be useful to use one negative and one positive. Lets say you had a three channel plane that really dropped the nose when you gave rudder input. RUDD > ELEV +25% / −25% or opposite values would give some automatic up elevator when you input rudder through a turn. The AUX2 > Thro mix doesn't work that way for some reason only the code writer would probably know. The effect of a negative or positive rate is more like that of an offset. Something peculiar to the throttle channel I suspect.

I've always been puzzled by that AUX2 > THRO mix. Just seems odd to me. It seems to work well though if your goal is to use the AUX2 switch.

There is another one I come across a lot.

THRO > THRO
rate: −100%
------ −100% - there doesn't seem to be any need for this rate. Works fine on 0%
offset −100

Is there any reason you don't use that? You have to use the mix, gear, or flap switch rather than aux2.
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Old 02-06-2013, 07:53 PM   #21
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Originally Posted by Turner View Post
THRO > THRO
rate: −100%
------ −100% - there doesn't seem to be any need for this rate. Works fine on 0%
offset −100

Is there any reason you don't use that? You have to use the mix, gear, or flap switch rather than aux2.
That's how i did it with my old DX7, just had the rate set to be activated by a spare switch. I used the switch on the top right that is the one that heli flyers use for throttle hold (seemed logical to me).

One of the many things I like about my new DX8 is that it has throttle curve programming which makes setting a kill switch dead simple.
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Old 02-07-2013, 12:47 AM   #22
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Again, the point here isn't to arrive at a throttle cut-off switch (or whatever) so much as to arrive at an understanding of the programming behind it.

As you can see by the attached images, I spent quite a bit of time trying to come to grips with this. Here is a link to an online spreadsheet with quite a bit of my data:
https://docs.google.com/spreadsheet/...Wc&usp=sharing

You say that an OFFSET of 100 doesn't nullify the mix, but it really, really seems to. No matter what RATE is set, be it negative or positive, large or small, -125 or +50, when the OFFSET is 100, the mix does nothing.


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Name:	XL01.jpg
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ID:	166114 Throttle programming results
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Name:	XL02.JPG
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ID:	166115 More throttle programming results

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Old 02-07-2013, 04:47 AM   #23
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I've said a couple times that a 100 offset does nullify a negative rate but this seems to be true only when the throttle channel is involved. Honestly, I would stop trying to understand why the throttle channel behaves this way. There is something peculiar about these throttle channel mixes. Rates behave like offsets and offsets behave differently than with other mixes. Knowing how rates and offsets behave in these two mixes is enough for me. I think the only one who could unravel this mystery is the guy who wrote the code and I doubt we will get any help on that.

More important to me is seeing how they work with other mixes and designing interesting and useful mixes.

Set this one up and try it. It shows in very straight forward and simple fashion what positive and negative rates do and then how positive and negative offsets effect the mix.

First go into Input Select and set AUX2 switch to INH.

Then set up a mix - ELEV >AUX2, rate: +100%/+100%, SW: ON

What you get is AUX2 following exactly ELEV. If you use −100 rates you get the same linear response but slave servo travel is reversed. Back to +100.

Now add positive and then negative offset. I find that using 25, 50, 75, and 100 give a better visual effect as it matches up nicely with the graduations of the monitor screen. The results are very straight forward and predictable. Any offset value moves the slave servos curve to left or right on the screen by the exact number of the offset. Left or right depending on + or −.

Something very different is going on with throttle mixes. I'm not really worried about that any more. We have two throttle kill mixes that work very well. I prefer the THRO > THRO mix because it doesn't tie up another channel and I'm inclined to want to use AUX 1 and 2 for wing servos. But if you weren't using AUX2 and wanted to use that switch, that mix works great too.

Things also get strange when you start mixing a channel to itself multiple times. I've been working on a mix for a four servo wing that uses flaperon wing type, aileron differential, and separate three position flaps. Most important, this allows aileron differential plus some small amount of flaperon with three position flaps, regular aileron function with three position flaps, and spoilerons with three position flaps. It's a little cumbersome requiring three switches and a lot of rate, offset, and end point adjustments but it works.

I don't want to hijack your thread but this might be a good place to post different mixes for reference If that works for you.
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Old 02-08-2013, 09:53 PM   #24
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Ah-ha. So throttle mixes are weird and eldritch. You're saying that maybe, just maybe, I can come to understand mixes if I leave the throttle alone, as it acts differently.

That is good and valuable to know. i was beginning to think I was demented.

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Old 02-08-2013, 11:02 PM   #25
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Yeah, that's the way it looks to me.... Oh, not the demented part. Ha Ha

Lets keep this discussion going and post up different working programs or programming questions if you like. DX7 interest is dying out.
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