Spektrum mix to invert gyro gain for rescue activation

[Smoggie]

So in my normal flight modes I have three different headspeeds with three different tail gain values, each optimised for the specific headspeed;

e.g.:
FM1 = 1800RMP & 60% gain
FM2 = 2000RPM & 55% gain
FM3 = 2200RPM & 50% gain

When I activate rescue I need negative values. I'd like these negative gain values to be exact 'mirror imaged' to achieve this:
FM1 = 1800RMP & -60% gain
FM2 = 2000RPM & -55% gain
FM3 = 2200RPM & -50% gain

So is there a way to do this using mixes in a DX18 ? I've tried a conventional mix but it doesn't quite achieve what i want. For instance If I use (say) a -110% mix I get:
FM1 = 1800RMP & -50% gain
FM2 = 2000RPM & -55% gain
FM3 = 2200RPM & -60% gain

This is ok if I'm in FM2, but the gains are wrong for FM1 or FM3

Any 'mixing wizards' out there?.. Maybe it cant be done?

[Smoggie]

ok, I figured it out. To do it you need to set a GER>GYR mix with values of -200% / 0% . The mix is activated off the rescue switch.
The tricky bit is that the maximum mix is only 125% so you need to use two mixes each set at -100% which add together to give the required -200%

[jgiannakas]

Originally Posted by Grumpy_Old_Man

ok, I figured it out. To do it you need to set a GER>GYR mix with values of -200% / 0% . The mix is activated off the rescue switch.
The tricky bit is that the maximum mix is only 125% so you need to use two mixes each set at -100% which add together to give the required -200%

Yeah exactly what I've done too on my dx6i

[Smoggie]

Originally Posted by jgiannakas

Yeah exactly what I've done too on my dx6i

Yes, it 'clicked' just before I read your post in the other thread!

[jgiannakas]

Originally Posted by Grumpy_Old_Man

Yes, it 'clicked' just before I read your post in the other thread!

Yeah took me a good hour or so to figure it out and that was by plain luck! Would have thought that you couldn't add two mixes on the same channel
And on the same switch, especially as it doesn't let you go over 125% on one mix!

So I've swapped the trainer switch with the ail DR switch and moved it on the top right corner - that should do for easy access to the bailout function! Ordered a momentary button switch as well but will see whether it's more convenient ...

[Smoggie]

Sounds like we are on the same page on a few counts. I added a momentary switch to my Tx too, in the top left position. The switch is Futaba part number: 3M94A00907 I found it on eBay.

It's an exact match for the Spektrum long switches.

[Coco66]

Grumpy_old_man and jgiannakas, I think you guys are still talking two different things.

Grumpy_old_man, on the DX18, I think you can assign a mix to a switch, and that is what you are doing, correct?
So you are basically mixing the gyro gain channel onto itself, when the switch is activated.
I am pretty sure you can use one single mix, with -100% and OFFSET 100% to achieve the same that you have now, that is: perfect "reversal" of the value of the gyro channel.

Instead, jgiannakas, I assume you with a DX6i have the same problem as me with the DX8: you have to assign an unused channel to the switch (say, AUX2) and mix THAT into the gyro channel, so you will never achieve a perfect mathematical "reversal" of the value of the gyro channel, but if you change the gyro gain value you will have to change the "negative" value of the mix to reverse it properly. And you will have the same negative value when activating Rescue regardless of the FM you are in, because the current value of the gyro channel is not accounted for in the mix.
Still, I think you can also do it with a single mix changing the OFFSET to 100%.

If I am wrong, please tell me, I am still looking for a better solution with the DX8...

[Smoggie]

Coco66,

No, using offset doesn't work, i tried it. The problem with offset is it's a fixed value that simply moves the centre point by a fixed %. To make this work you have to have the mix proportional to the gyro input, but opposite.

But yes, i did it by mixing the gyro channel ('gear') to gyro. So in the mixing menu that's GER>GYR. This is the same for both mixes. The mix is activated by the same switch I use for rescue. Rescue itself is done using bank switching in the spirit from Aux2 channel.

Here's a photo of the mix I used, this has to be duplicated on on Mix 2 also:

[Coco66]

Originally Posted by Grumpy_Old_Man

Coco66,

No, using offset doesn't work, i tried it. The problem with offset is it's a fixed value that simply moves the centre point by a fixed %. To make this work you have to have the mix proportional to the gyro input, but opposite.

But yes, i did it by mixing the gyro channel ('gear') to gyro. So in the mixing menu that's GER>GYR. This is the same for both mixes. The mix is activated by the same switch I use for rescue. Rescue itself is done using bank switching in the spirit from Aux2 channel.

Just to understand, why do you need a different bank for Rescue?
Which settings you have different in that bank?

[Smoggie]

Originally Posted by Coco66

Just to understand, why do you need a different bank for Rescue?
Which settings you have different in that bank?

I didn't 'need' a different bank, it would have worked by just assigning a flight mode for rescue. The reason i prefered bank switching was that way i could rescue using whatever headspeed I was flying at without rescue activation also causing a change in headspeed. I figured that performing rescue while also changing headspeed might cause issues.

If doing rescue off a flight mode then it would have saved me all the trouble of doing this mix, I could have simply used a gain value assigned to the rescue flight mode... But i guess I like to make things difficult!

[Coco66]

Originally Posted by Grumpy_Old_Man

I didn't 'need' a different bank, it would have worked by just assigning a flight mode for rescue. The reason i prefered bank switching was that way i could rescue using whatever headspeed I was flying at without rescue activation also causing a change in headspeed. I figured that performing rescue while also changing headspeed might cause issues.

If doing rescue off a flight mode then it would have saved me all the trouble of doing this mix, I could have simply used a gain value assigned to the rescue flight mode... But i guess I like to make things difficult!

You ARE making it too complicated ))))

Forget about the Spektrum manual you see on the Spirit forum.
That's for 6 channel radios.

Just keep bank 0, and setup the Rescue you want, there, in the Stabi tab.
Setup your TH behaviour and FM behaviour in an absolutely normal way, like you have always done before Spirit.

Your mix will activate Rescue by inverting the Gyro value to its negative.

No change in Throttle Curve nor in Pitch Curve.

As simple as that.

[Smoggie]

Originally Posted by Coco66

Your mix will activate Rescue by inverting the Gyro value to its negative.

Good call!

I think i probably had it in my head originally when did it with the flight modes that it would give me the option of having rate mode and/or stability mode in addition to rescue. But the reality is i have no use for either of those, so I might as well keep it simple.

[Smoggie]

Originally Posted by Coco66

You ARE making it too complicated ))))

So after much pondering i've decided to keep the bank switching, but i've allocated the bank switch channel (aux2) to my flight mode switch. This way I can set different head gain values per bank to my different flightmode headspeeds. Using this I've managed to dial out some nodding i had at lower RPM without compromising head gain setting at higher RPM.

This also allows me other tweaking such as setting higher rescue collective for lower RPM flightmode.

I think I've now got whats for me close to the perfect setup, it took a while but i got there eventually!

[Coco66]

Good idea!

That's the correct use of banks if you have more than six channels.

I will soon use banks to try Stabilization, did not do that yet. I am familiar with the concept thanks to my small quads, but did not try on a heli yet.

[chrisd1972]

Grumpy_Old_Man, could you maybe share your setup of DX18 in a bit more detail?

I have a DX9 and I think your settings may help me with what I want to achieve.

Idealy I would like to be able to have the following:

3 flight modes with 3 different head speeds / gains

From any of the flight modes I would like to be able to activate either stability mode or rescue mode.

I am assuming I will need to do some creative mixing etc.

Would also like to have the Stability mode activation on one switch e.g. Switch F on DX9 - Top right and the Rescue on a different switch e.g. Switch C position - Top Left - will be moving bind to this position and replacing with momentary.

Hope I have explained that ok.

Any pointers, ideas etc. will be welcome.

I know this is quite a complicated setup, but I would like to be able to do all of these functions so I can demo the unit to potential buyers, so the more options I can demo, the better.

I can set this up on the Original Red Spirit or the Spirit Pro - have both.

Currently using a 6ch Rx wired to the Spirit (Red) on my Trex 550, but can replace with an AR8000 or AR9020 if that will give me more options.

[Smoggie]

Originally Posted by chrisd1972

Grumpy_Old_Man, could you maybe share your setup of DX18 in a bit more detail?

You need seven channels to do bank switching.

Having stabilisation AND rescue would make it more complicated. You would need a bunch of mixes. I think the easiest way would be to have two switches each mixed to produce a certain offset of the bank switch channel, plus activate their own set of two negative gyro mixes (as described previously). It's kinda hard to describe in words.

[Coco66]

You can still do bank switching with six channels, but since you need to use one bank for normal flight, one for stability and one for rescue, you will end up with the same gyro gain for all your flight modes since you will need to setup the gyro gain in the Spirit software and use channel six for the bank switching.