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Old 09-29-2020, 09:36 AM   #60 (permalink)
MKL.DKM
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Join Date: May 2011
Location: Westmalle
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Quote:
Originally Posted by ArchmageAU View Post
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

My main abuse for mixing is to get more idle up modes (6) for my 130x. Next is to allow rescue on my X5 through the BD3SX.


6 Idle up modes

To get the 6 idle up modes (100, 95, 90, 85, 80 and 75% flat throttle) I use the following 2 mixes.

Mix 1 - Ax2 > Thr 0% -10% 100% (f.mode 2)
Mix 2 - Ax2 > Thr -10% 0% -100% (f.mode 1)

My throttle channel is flat 85% for UI1 and 100% for UI2 . Aux2 is controlled by the Gov switch.

What this does.

When Gov is in pos 0, it output Aux2 +100. Gov pos 1 = Aux2 0. Gov pos 2 = Aux2 -100.
  • In f.mode 2 and gov 0 (top), throttle is 100% (Mix 1 - 100% offset, so master channel at 100 means 0 change).
  • In f.mode 2 and gov 1 (middle), throttle is 95% (Mix 1 - 100% offset. At master value of 0, -10 is applied as master channel is -100 compared to offset (-10 = -5% in throttle terms)).
  • In f.mode 2 and gov 2 (bottom), throttle is 90% (Mix 1 - 100% offset, At master value of -100, -20 is applied as master channel is -200 compared to offset (-20 = 2*-10 as master channel is 2 times further than endpoint from offset). (-20 = -10% throttle terms)).
  • In f.mode 1 and gov 2 (bottom), throttle is 85% (Mix 2 - -100% offset, so master channel at -100 means 0 change, Throttle curve is 85% of UI1).
  • In f.mode 1 and gov 1 (middle), throttle is 80% (Mix 2 - -100% offset. At master value of 0, -10 is applied as master channel is +100 compared to offset (-10 = -5% in throttle terms)).
  • In f.mode 2 and gov 0 (top), throttle is 75% (Mix 2 - -100% offset, At master value of 100, -20 is applied as master channel is +200 compared to offset (-20 = 2*-10 as master channel is 2 times further than endpoint from offset). (-20 = -10% throttle terms)).

BD3SX rescue with auto level

My X5 mixes are for rescue facility on the BD3SX and mix Aux3 to pull the Aux2 channel to full negative when the Aux3 goes to -100 (Aux3 is assigned to my bind button, Aux2 channel is the BD3SX SL channel and assigned to the Gov switch).

To pull the Aux2 channel to full negative when the Aux3 goes to -100 I use the following single mix.

Mix 6 - Ax3 > Ax2 0% -125% 100% (f.mode N12H)

As the Aux 3 channel moves from +100 (no change) to -100, its change relative to the offset is -200 (200%), so -250 (or 2*-125) is applied to the Aux2 channel. This single mix ensures that no matter what the value of the self level (I have only up to 45%), it will pull it to full negative.

The last bit of magic, is during this rescue, I also want to centre the cyclics (elevator and aileron). I was told this cannot be done (which is why the investigation into mixing). I found a way.

Mix 1 - Ax3 > Ail 0% -125% 100% (f.mode N12H)
Mix 2 - Ax3 > Ail 0% 75% 100% (f.mode N12H)
Mix 3 - Ax3 > Ele 0% -125% 100% (f.mode N12H)
Mix 4 - Ax3 > Ele 0% 75% 100% (f.mode N12H)

Like the previous Aux2 channel, I pull the channel, hard to it's bottom limit (wiht Mix 1 and Mix 3). With Mix 2 and 4, I push it back to the dead center.

Now my BD3SX rescue auto-levels on my DX8


Congratulations if you made it to the end of this epic.

Hope this helps people.
After so many years I find a correct answer to use both functions of the 3SX, SL and CR. After programming your setting in my Spectrum DX8 everything works ... A 100 out of 100 for this solution .. Great
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