I don't understand my DX8 Mixing options

[truckermusic]

I know that we have this option available to us but I know nothing about it, how it works, or functions and what would it do for me....

I have never used mixing so I need a very basic explaination of what it does before I can formulate any kind of intellegint questions about it..

I have been working on the hobby since last year march and actually flying since last year August. So I have a bit of understanding of most of my radio functions and programming....just not mixing...

Since I am basically new to programming this unit and flying in general, meaning I am not bad at hovering (but still need work and want to be better) and I am just starting forward flight with very basic turns I am thinking that if I can somehow add (mix) a bit of rudder to the aileron (in headholding mode) it may just make it easier, and more proficient in my turning manuvers.

This is what I am thinking mixing "May" do for me....
If I move my aileron (left or right) X amount it will add in X amount of rudder to push the rudder in the direction I want to go thus rudder movement would be "somewhat" tied to Aileron movement. Thus Turns would be more consistent because rudder movement would be more consistent.

Also I would like to understand if I can some how make my head speed more consistent with mixing (and not a Gov....I understand gov's ) as well...

I may be all wet with this idea but that is what I would like to find out...

thank you

[flightengr]

Mixing tends to be a very difficult subject to explain. Part of the reason is that it's one of those things that's so flexible that it often doesn't make sense without a specific example. The only transmitter manuals I've been exposed to, the Spektrum manuals, do a very poor job of explaining what it is and how it works - they only tell you how to enter values on the mixing screen.

In short, the whole idea of mixing is to make one control input on the transmitter automatically change the value of another control input. Your first example is a good one - you can use a mix to add some input to the rudder based on the position of the aileron stick. Mixing can do more creative things as well. For a collective-pitch helicopter, setting the swash type is really enabling an automatic mix of elevator, aileron, and pitch channels built into your controller. The inputs used in a mix don’t have to be stick inputs; you could even mix switch inputs to create the effect of a three-position switch using two two-position switches.

Mixes are created in the Mixing section of the Function menu. To create one, you would go there, and then you can start to edit "Mix 1".

The first detail you need to provide is which channel will drive the mix as the master channel, and which channel will be modified as a result of the mix as the output channel. This is displayed on the screen as "master > output". So for your example, you would set up a mix for "AIL > RUD".

Next there are two values listed under "Rate". How the Rates are applied is determined by the value of the "Offset". The Offset can be thought of as the center point of the mix. The output of the mix is always 0% at the Offset point. The top value of Rate is used when the master input is above the Offset value, and the bottom value of Rate is used when the master input is below the Offset value. The easiest example is when the Offset is at 0%, as that would also correspond to center stick.

The Rate is a multiplier that is applied to the amount of change in the master input in order to compute the amount of change that will be added to (positive rate) or subtracted from (negative rate) the output channel. A Rate of 100% would make the output channel change by the exact same value as the master input channel changed. A Rate of 50% would add only 50% of the master input's value to the output channel.

Let's try making this a more concrete by adding some rudder based on the aileron input. I'll use 20% as the Rate, so when the aileron moves 10%, the transmitter will add 20% of that amount (20% of 10%, or 2%) to the rudder channel. I'm going to leave the Offset at 0% (center stick).

So if I set up the mix this way:

AIL > RUD
Rate:
20%
-20%
Offset:
0%

Then what will happen is that the rudder will move 2% for every 10% of aileron movement. The second value of Rate - the one used when the channel is below the Offset - needs to be negative in this case because of the way values are assigned on the channels. The DX8 uses 0% at the center of the stick, +100% at the top end of the stick (throttle/elevator) or at the left end of the stick (rudder/aileron), and -100% at the bottom of the stick (throttle/elevator) or at the right end of the stick (rudder/aileron). So when the aileron stick moves to the right, creating a negative value for aileron, you also want to subtract from the value of rudder to make it go to the right as well.

On the DX8, deciding whether or not a mix is "active" or "enabled" depends on the type of model. For an Acro (airplane) model, you can select a switch that will activate the mix. For a Heli model, a mix is associated with one or more flight modes.

There's one additional question you need to answer on the DX8 when you create a mix: "Trim" is either set to "Inhibit" or "Active". If Trim is set to Inhibit, then trim on the master input channel is ignored by the mix. If Trim is set to Active, then any trim on the master input channel is considered to be input by the mix.

That's the tip of a very big iceberg, but I hope that's enough to help you get started and try your first idea of adding some rudder automatically based on the aileron stick.

If you haven't discovered it already, the Monitor screen (Function Menu > Monitor) is a great way to watch how the outputs change on each channel as you move the sticks around. That allows you to test the mix and get a feel for how it works long before you power up your aircraft and really try it out.

[Gyropilot]

Thanks for taking the time to explain all that flightengr.

That's useful info!

[truckermusic]

Originally Posted by flightengr

Mixing tends to be a very difficult subject to explain. Part of the reason is that it's one of those things that's so flexible that it often doesn't make sense without a specific example. The only transmitter manuals I've been exposed to, the Spektrum manuals, do a very poor job of explaining what it is and how it works - they only tell you how to enter values on the mixing screen.

In short, the whole idea of mixing is to make one control input on the transmitter automatically change the value of another control input. Your first example is a good one - you can use a mix to add some input to the rudder based on the position of the aileron stick. Mixing can do more creative things as well. For a collective-pitch helicopter, setting the swash type is really enabling an automatic mix of elevator, aileron, and pitch channels built into your controller. The inputs used in a mix don’t have to be stick inputs; you could even mix switch inputs to create the effect of a three-position switch using two two-position switches.

Mixes are created in the Mixing section of the Function menu. To create one, you would go there, and then you can start to edit "Mix 1".

The first detail you need to provide is which channel will drive the mix as the master channel, and which channel will be modified as a result of the mix as the output channel. This is displayed on the screen as "master > output". So for your example, you would set up a mix for "AIL > RUD".

Next there are two values listed under "Rate". How the Rates are applied is determined by the value of the "Offset". The Offset can be thought of as the center point of the mix. The output of the mix is always 0% at the Offset point. The top value of Rate is used when the master input is above the Offset value, and the bottom value of Rate is used when the master input is below the Offset value. The easiest example is when the Offset is at 0%, as that would also correspond to center stick.

The Rate is a multiplier that is applied to the amount of change in the master input in order to compute the amount of change that will be added to (positive rate) or subtracted from (negative rate) the output channel. A Rate of 100% would make the output channel change by the exact same value as the master input channel changed. A Rate of 50% would add only 50% of the master input's value to the output channel.

Let's try making this a more concrete by adding some rudder based on the aileron input. I'll use 20% as the Rate, so when the aileron moves 10%, the transmitter will add 20% of that amount (20% of 10%, or 2%) to the rudder channel. I'm going to leave the Offset at 0% (center stick).

So if I set up the mix this way:

AIL > RUD
Rate:
20%
-20%
Offset:
0%

Then what will happen is that the rudder will move 2% for every 10% of aileron movement. The second value of Rate - the one used when the channel is below the Offset - needs to be negative in this case because of the way values are assigned on the channels. The DX8 uses 0% at the center of the stick, +100% at the top end of the stick (throttle/elevator) or at the left end of the stick (rudder/aileron), and -100% at the bottom of the stick (throttle/elevator) or at the right end of the stick (rudder/aileron). So when the aileron stick moves to the right, creating a negative value for aileron, you also want to subtract from the value of rudder to make it go to the right as well.

On the DX8, deciding whether or not a mix is "active" or "enabled" depends on the type of model. For an Acro (airplane) model, you can select a switch that will activate the mix. For a Heli model, a mix is associated with one or more flight modes.

There's one additional question you need to answer on the DX8 when you create a mix: "Trim" is either set to "Inhibit" or "Active". If Trim is set to Inhibit, then trim on the master input channel is ignored by the mix. If Trim is set to Active, then any trim on the master input channel is considered to be input by the mix.

That's the tip of a very big iceberg, but I hope that's enough to help you get started and try your first idea of adding some rudder automatically based on the aileron stick.

If you haven't discovered it already, the Monitor screen (Function Menu > Monitor) is a great way to watch how the outputs change on each channel as you move the sticks around. That allows you to test the mix and get a feel for how it works long before you power up your aircraft and really try it out.

flightengr

Thank you for this explaination.....I can see why not a lot of people want to undertake the task of understanding this.....But this is a very nice write up!!

I will have to re-read this a few times but given the fact that you gave me a great example and starting point and then an exercise to work on (meaning try things on a blank channel and watch the monitor screen) I will be able to get this far....

I really do want my ailron's input to affect my rudder but I can also see that it can mess me up a bit say when I want to come out of the turn and just want to level out the heli.

or say if I am hovering and need some Aileron correction then it will affect my corrections.....

So I am going to guess-ta-mate that I am going to have to have a fine line between turn aileron input and correction input.....

this is going to take some experimenting...

Thank you for this and I am sure that I will have quesions later

Clifford

[truckermusic]

Originally Posted by flightengr

On the DX8, deciding whether or not a mix is "active" or "enabled" depends on the type of model. For an Acro (airplane) model, you can select a switch that will activate the mix. For a Heli model, a mix is associated with one or more flight modes.

OK, So after reading SLOWLY I understood your explaination ....so my first question for you

If I am in a Heli model and the mix is associated with one or more flight modes.

How do I know which flight Modes the mix is activated in?
How do I program a mix to work in one or more flight modes?


thanks

[flightengr]

The DX8 puts a number of little boxes at the bottom of the mix screen like N, 1, 2, etc. for each flight mode. If you select a box and turn it black, then the mix is active in that flight mode. You can select more than one flight mode.

[truckermusic]

Originally Posted by flightengr

The DX8 puts a number of little boxes at the bottom of the mix screen like N, 1, 2, etc. for each flight mode. If you select a box and turn it black, then the mix is active in that flight mode. You can select more than one flight mode.

I see!
That is pretty cool!!!

OK next question.....will mix options work in Phoenix ? The flight sim??

[flightengr]

Yes, they work in Phoenix too.

[ArchmageAU]

I did a thread on: Solving the DX8 spectrum mix setting mystery.

Originally Posted by ArchmageAU

Ever wondered what the numbers in mix setting mean on the DX8 in heli models?

You have:

• Master channel
• Slave channel
• Rate: <high percentage> <low percentage>
• Offset: <percentage>
• Trim: <INH/ACT>
• Flight Mode: N12HM

To most except the Spectrum Inner sanctum, these have remained a source of trial and error.

The text from the manual is:

The above offers almost no explanation of how the numbers really work.

What is really going on.

I'll ignore the trim, but expose the rest.

The master channel is the control channel. It's current absolute value (from -150 to +150) is what is important here.

The slave channel is the control channel being altered. It plays only a "carrier" role of the output value from the mix. The mix value derived from the master channel is simply added to the output value on the slave channel.

The Flight modes are fairly self explanatory except for M. M (Mix) is the Gear switch in HELI mode. The great thing about this is now you have a 2 position switch that can be used to enable and disable a mix for ALL flight modes. Gear 1 is mix enabled, Gear 0 is mix disabled. Be careful when using this as it ALWAYS applies regardless of the flight mode. (ie. if you use this for throttle manipulation, it will also manipulate when throttle hold is on).

Now to mix numbers.

Think of the high rate percentage and the low rate percentage as the value the mix will have if the master channel is at +100 and -100 respectively. When the master channel is 0, it will have a value of 0 (irrespective of these other rate numbers). The adjust value of the mix changes linearly as the mix channel moves from centre to (OR PAST) either of these end points.

Offset is where it becomes tricky. Offset is how far to move this entire range so 0 has no change. This is where most peoples brains explode or implode.

If we have an offset of 50, The master channel must be at 50 for no change to slave channel. With this same offset of 50, if the master channel is at -50, the low rate is applied. With this same offset of 50, if the master channel is at -100, 1.5 times the low rate will be applied. With this same offset of 50, if the master channel is at +100, 0.5 times the high rate will be applied to the slave channel.

Last point is that mixes are applied cumulatively. If you have two mixes that affect the same slave channel, both output changes will be applied. That changes will be applied in the order of the Mix configuration. ie. Mix 1 is evaluated first, then Mix 2 (and so on). One other note on this is that all mixes occur to channel outputs and are not available as master inputs for other mixes. ie. If Mix 1 changes Aux2 output, and Mix 2 uses Aux2 to change Throttle, the alterations to the Aux2 output will not be used for the Mix 2 input (as it uses the source Aux2 value).


Uses and abuses for Mixing

....

This seems to have gotten lost in time.

I had a DX8. Was useful to know this stuff when programming it (or any other DX<n> radios.

Hope this also helps clarify for the OP (or anyone else stumbling across this thread).

[truckermusic]

Arch..

You my friend are the MASTER and I mean that sincerly sir....You ALWAYS have these in depth explainations on topics which for this poor old soul I have to read and re-read and re-read and re-read til I can understand them....but that is ok...it gives me something to look forward to and to push my learning skills....So I love them...

What I needed right now was a very simple explaination and Flight Engr's some how (and I needed to read and re-read his as well) just worked for me....

But PLEASE KEEP ANSWERING ME WITH YOU EXPLAINATIONS...they are always welcome kind sir.....

thank you

[truckermusic]

Originally Posted by flightengr

Yes, they work in Phoenix too.

Well last night I went home and opened up my Dx8 and started messing around with a simple Ail>Rud mix as you suggested..

The nice thing about it was they have a monitor on the left hand side of the screen that I could watch what was happening....

I was able to program it for Flight mode 1 because I keep Normal for Hover, Landing and Take off's...

Now I did try them in my sim but I did not see or feel a change so maybe 20% is too low....I will have to keep experimenting...

But it was Dog Gone COOL!!!

[ArchmageAU]

Originally Posted by truckermusic

Arch..

You my friend are the MASTER and I mean that sincerly sir.......

What I needed right now was a very simple explaination and Flight Engr's some how (and I needed to read and re-read his as well) just worked for me....

But PLEASE KEEP ANSWERING ME WITH YOU EXPLAINATIONS...they are always welcome kind sir.....

thank you

Thank you. I will endeavor to keep answering (time permitting).

Not offended in the least that flightengr's response was much better tailered. I'm glad you are starting to get an understanding.

Originally Posted by truckermusic

...
The nice thing about it was they have a monitor on the left hand side of the screen that I could watch what was happening....
..
Now I did try them in my sim but I did not see or feel a change so maybe 20% is too low....I will have to keep experimenting...

But it was Dog Gone COOL!!!

Yep. Good that there is a monitor to show what is happening.

Do you have a specific goal in mind, or just learning?

If just learning, here are a few simple ones to try to see what is happening (all offset 0 so no really crazy stuff). All in the format of input > output high low offset. Enable for flight modes N12H.
- Ele>Rud 50 -50 0
- Ele>Rud 50 50 0
- Ele>Rud -50 -50 0
- Ele>Rud 0 -50 0
- Ele>Rud 100 0 0
- Ele>Rud 25 -50 0
- Ele>Rud 25 -50 0

Ensure your Elevator DR is 100 (expo whatever you like).

Move the Elevator from stick down (low) to stick up (high) and watch the change in the rudder (low is nose right, high is nose left).

Once you really understand mixes you can do some way cool stuff with them. Like in-flight tune the gain on your gyro by pot, but only when a certain switch is set.

On the BD3SX I had one switch for self level and another for rescue. I also mixed out the Ail and Ele during rescue.

Have fun.

[truckermusic]

Originally Posted by ArchmageAU

Do you have a specific goal in mind, or just learning?

Yes and Yes

A bit of background on why I am intrested in this...
Ray from Ray's authoratative instructional DVD's talk a small bit about this and it is over my head right now but I can see where it could be a very useful tool.

So I WANT to understand How to use (program) this feature..

Specific Goal(s):
For now...I guess as I progress I will find more goals...but for now,
1. Have the Ail affect Rudder movement to help me make turns
2. Have the Ail affect the trottle to keep it more constent in turns

For number 2 I know I could use a Gov. but at this point I do not and this will give me a chance to understand mixing programing.


Next question for the Both of you guys:

How does D/R and Expo affect a mix?
Thanks

[truckermusic]

??

[flightengr]

I'm not 100% sure... I think D/R and expo would be applied to the input channel before the mix, and then the mix output is calculated after that? I haven't tried it.

[aerocal]

The D/R and Expo act on the stick input itself. Mixing acts on the channel value.So for example you have 50% Ail rate and you then make an Ail>Rud mix with 50% Rates both ways. With full Ail stick deflection the total value of Rud output will be 25%. Then if you keep the same 50% Ail rate but have a Mix of Rud>Ail
with 50% rates and you deflect the Rud stick fully you will have a total output on Ail channel of 50%.

D/R and expo do the math between the stick value and the channel value.
Mixing does the math between the channel value and the Slave.
The total output value of the stick itself is based on the Travel setting.

[aerocal]

Originally Posted by flightengr

I'm not 100% sure... I think D/R and expo would be applied to the input channel before the mix, and then the mix output is calculated after that? I haven't tried it.

Trucker asks good questions. I understand the whole system but my trouble sometimes is putting it into understandable words.
I love these kinds of threads. It makes me think and I learn some things too. For me its the biggest reason we are here.

[ArchmageAU]

Originally Posted by truckermusic

Yes and Yes
...

So I WANT to understand How to use (program) this feature..

Specific Goal(s):
For now...I guess as I progress I will find more goals...but for now,
1. Have the Ail affect Rudder movement to help me make turns
2. Have the Ail affect the trottle to keep it more constent in turns

For number 2 I know I could use a Gov. but at this point I do not and this will give me a chance to understand mixing programing.


Next question for the Both of you guys:

How does D/R and Expo affect a mix?
Thanks

OK. aerocal and flightengr pretty much nailed why DR affects mixes. DR (and expo) is applied BEFORE mixes (to create a channel value).

Now the hard part (where I unfortunately rain on your parade).

1) "Have the Ail affect Rudder movement to help me make turns".

Unfortunately, your turn rate HEAVILY depends on your lateral speed (Something your TX does not know). eg. Backward turns, the rudder is in reverse. High speed turns have high bank angle, little rudder. Very slow turns have MUCH more rudder than Aileron. Stationary turns (piros) are ALL rudder.

Unfortunately it means that whatever you put in this mix it will make things worse, not better.

2) "Have the Ail affect the throttle to keep it more constent in turns".

Unfortunately, this falls into the same category as rudder. In simplified terms, a portion of your throttle is used to balance the change in inertia (a force required to deviate the center of mass of an object from its previous path) of the heli in the turn. The faster the turn, the greater the inertia to be countered, the greater the throttle adjustment. (There is A LOT more going on, but this is probably the major force to be countered).

So unless you can gauge the inertia, the throttle adjustment on aileron will make things worse more than help.


One heli mix that does make sense was Revo mix, but this was for older helis with only rate mode gyros. Revo mix tries to counter the torque changes generated by collective adjustment on the tail (at constant throttle). In most moves, this extra load (and torque increase) was fairly consistent, so a mix could counter it. Where things could go wrong was in rapid un-loading or auto-rotation, but the revo-mix was so small that the average pilot could steer through it with ease in those situations..

Let me not dissuade you learning mixes though. They are quite useful. More so in planks than helis (essential in gliders). However in helis it opens up more possibilities as to what you can do with the heli (like more flight modes, tuneable DR, etc..).

Best of luck.

P.S. One of the best things you can do for the tail to smooth things out is add expo. You can "feel" your way round a turn, but sill have max rate for stall turns. For throttle management in turns, nothing beats a governor to counter the collective loading by change in inertia.

[truckermusic]

Thanks guys...\

right now I am letting this stuff run around my head as I try out different things....

I already have a few questions but am going to wait because maybe I will answer them my self...

But I will ask if I cannot.

Thanks Again
Clifford

[aerocal]

At the bottom of the Mix menu screen there is a row of boxes. Making a box Black enables it in that mode. M is the Mix switch.