Mixer (6/13)

When you’re ready, SP PAGE into the “Mixer” screen (pg 6 of 13).

We’ve just finished the first link in the command chain of setting up your model by defining the inputs to our virtual channels in the Inputs screen. The Mixer is the next step in the command chain, and it defines how a virtual channel becomes a real radio channel at a specific receiver port. For example, Channel 1 in the Mixer is Channel 1 on the receiver. (Hmm… this still doesn’t seem hard to understand).  At a minimum, we must have a channel assigned to each servo controlling the aircraft.

You’ll notice that the Mixer screen has a familiar look from the Inputs screen, and many of the fields work the same way.  Like the Inputs screen, the Mixer uses multiple lines of definition to configure each channel the way we want it.  The button navigation to add/edit/copy/move/delete lines for each channel also works the same way. So you already know a lot about how to use the Mixer.

A key feature not seen in previous screens is the ability to combine multiple inputs into one output (called multiplexing) using Add, Multiply, Replace logic.  We’ll leverage your knowledge with a brief overview of the Mixer fields, then we’ll cover the class set up (always shown in green font).  The Glossary remains on standby to help.

  • Mix Name:  A name can be entered as a reminder of the purpose of that line.
  • Source:  The Inputs screen configured a raw stick input into an input control channel  with switch selectable weights and expo values.  We will use those configured Inputs in the Mixer, e.g., IAil for the aileron input.
  • Weight:  This is the weight (in %) to be applied to the input to determine how much of the input channel gets into the output from the mixer. The default is 100% for all lines but 0% to 500% can be entered here to achieve the desired ratio of different inputs into one output.  Once the proper ratios are achieved, a Mixer channel output that exceeds 100% is clipped, or stopped, at 100% to be passed on to the Servos screen where the final control throw is determined with travel limits and servo reversals are defined.

An example is adding a small portion of the aileron channel into the rudder channel to coordinate turns.   It is recommended to use 100% for the incoming control channel (rudder in the example) into which portions of other inputs will be mixed (aileron in the example) to make it easier to size the inputs to one another.  A negative value for weight in the Mixer will invert the response, but this is used only to affect the relationship among mixed inputs, not to reverse servos (more about this in the Servos and Takeaways screens.  Another example — you might need a small potion of the rudder channel to be added to or subtracted from the elevator channel to correct pitch coupling in knife edge.  The Mixer is the place to blend inputs, and the Servos screen (up next) is the preferred place to reverse servos and set final control throw for the highest rate condition.

  • Offset:  A fixed value can be added or subtracted from the input value here if needed.  Examples in the Glossary definition.
  • Trim:  For sticks, the default is the trim previously associated to the stick in Inputs, but can be chosen to be one of the other trims, e.g., cross trims, or trim can be disabled altogether. For non-stick inputs the trim defaults to OFF, but can be set if desired. Note:  Trims must be included (ON) in both Inputs and Mixer for the trimmer value to be passed to the servos.
  • Curve:  Either a differential value can be set (to reduce response by the specified percentage on one side of the throw) or a curve (built-in or custom) can be assigned. When a custom curve is selected, a press of the MENU key will take you to the curve editor.  Custom curves will be covered in a later class. Check the Glossary for more information on differential.
  • Modes:  The flight modes can be selected in which a mixer line is active.
  • Switch:  A switch (physical or virtual) can be used to activate the mixer line.
  • Warning:  A sound warning (1, 2 or 3 beeps) can be set to play whenever the line is active.
  • Multpx:  The Multpx setting defines how the current mixer line interacts with the others above it on the same channel. “Add” will simply add its output to them, “Multipl” will multiply the result of the lines above it, and “Replace” will replace anything that was done before it with its output. The combinations of these operations allow creating complex mathematical operations.
  • Delay Up/Dn:  Response of the output can be delayed with regard to the input change by the selected seconds. Useful for a sequence of actions that should not begin simultaneously.
  • Slow Up/Dn:  Response of the output can be delayed with regard to the input change by the selected seconds.  For example, deployment of flaps could be slowed down to minimize ballooning the model.  The time is how many seconds the output will take to cover the -100 to +100% range.

Our basic airplane set up will not need many of these features.  The simple 5-channel model will have only one line for each of the four basic sticks for the desired radio channels plus one more aileron input to a 5th channel to control the opposite aileron.  Let’s step through it:

  • We defined A,E,T,R as our preferred order of control channels in setting up the radio, so that is the order that our channels will be presented to us in the mixer.  The actual order doesn’t matter because we can map the inputs to any receiver channel that we want.
  • The class example names Channel 1 as ‘Ail Rt’ and uses the IAil input source (recall that IAil is the configured Aileron from the Inputs screen rather than the raw stick input).  Otherwise all the other default fields for Ail Rt are correct as displayed in the mixer.
  • Similarly the Elevator, Throttle, and Rudder are correct as displayed.  Since I’m running electric instead of wet power, I prefer to rename Channel 3 to Throttle instead of Engine.
  • The class example controls the Ail Left servo at channel 5.  We’ll use the COPY and MOVE selections rather than EDIT to put a copy of  the Ail Rt line into channel 5 and label it Ail Left.  We need some further thought development here.  Aileron servos typically are installed in a mirror image to one another in the left and right wings.  If the two aileron channels both have the same sign (both increasing or both decreasing together) then both servos should rotate in the same clockwise or counterclockwise direction .  For mirror image servo installations, rotating in the same direction causes one servo to push on the control surface while the other pulls — opposite control throw in the two ailerons, which is exactly what we want.  We won’t know if they’re moving in the correct direction until we hook up the Rx and test the response, but we know that the same weights and signs for left and right aileron channels should give us opposite control throw for typical dual aileron installations.  The channel monitor at this point will show our channels moving in the same direction while the actual control surfaces are moving opposite one another, and they will be both correct or both reversed from your stick input.  If you prefer to have your channel monitor show left and right ailerons moving with opposite signals, then you should expect to reverse one servo in the final set up.  If you’re OK knowing that same-sign aileron signals will have opposite aileron control throw, then you will either have both correct or both will have to be reversed in Servos.  This becomes a personal preference, and now you can decide which way you like it.  For our class example, we elect to use -100 weight for the left aileron and we’ll reverse direction as necessary in Servos.  Exit to finish.

Your screen should resemble this one (click to enlarge; BACK to return):

Basic Airplane Pg 6

Basic Airplane Pg 6

Another check at the Channel Monitor is helpful to visualize the effects of choices made in the Mixer.  LP MENU to the Channel Monitor and EXIT to return.  Click to advance to Servos.


Mixer (6/13) — 9 Comments

  1. I have a scale C130 with flaps using individual servos for each flap. I can’t use a Y connector because the servos will travel in different directions and I don’t want to A) open up the servo and change the pot wires or B) buy a servo reversing Y connector and was wondering if I could put each flap servo on it’s own switch channel then do a mix where just ONE switch will activate both servos. SO the short is can I control 2 different channels with one switch?


    • Hi, Kyle!

      You can definitely control more than one channel off of a single switch. However, without separate signal wires going to each servo, I’m not sure just how you’d establish separate controls because the servos still share a common source.

      Sorry I couldn’t be of more help.

      Leonard (mac44mag)


    • Hi Kyle — Apologies for the delay in replying. Normally I get a notification from the site for new Comments, but I must have missed this one. I concur with Leonard’s comment. YES, you can control 2 different channels with one switch. But NO you can’t make the servos go in different directions without separate leads to the two servos. Not sure why you’re reluctant to use a Y-splitter with a reverser on one side. I’ve done that several times with good success. They aren’t expensive and they can let you adjust the servo centers independently. Regards………. Bob R.

  2. I’m trying to set Throttle end points on a wet power plane. My Taranis Plus Mixer screen does not have physical channel assignments yet, therefore I’m unable to set end points in “Servos” screen 7/13 in the radio. You mention “The class example controls the Ail Left servo at channel 5. We’ll use the COPY and MOVE selections rather than EDIT to put a copy of the Ail Rt line into channel 5 and label it Ail Left.” Is there a video showing this copy/move operation; or is it easily explained?

    • Hi Robbie — You have several considerations rolled into two brief messages. I’ll try to respond to them as best I can.

      — We created the OTXU to provide instructional resources in an organized way, and to that end we want to clarify and correct our instructional materials wherever it’s needed. One of our limitations is that our work may not be exactly correct for older or newer editions of firmware or equipment that we haven’t even had available to our small group of writers yet. The best place for questions involving older or newer equipment/firmware than listed in the assumption of our classes, is the RCG forum. There you will find many willing experienced users who probably will know the answer to specialized questions from first hand knowledge, while we can’t always do that. In this case, my class information wasn’t developed with the Taranis Plus, so I can’t speak from first hand knowledge about what you might be seeing. You might need to take Taranis Plus questions to the forums until our classes are updated to the latest/greatest equipment. Generally we don’t expect large changes, so the material that we provide can help even if it’s not perfectly aligned with your set up. But keeping up with the fast pace of change in this arena is a problem for us as well as the rest of the community.

      — You followed your initial comment/query with a “test message” because your initial comment didn’t show up immediately. I’ve not approved the test message for posting; this is a moderated area and not an instant messaging board or forum like RCG provides. Obviously if we become a place for thousands of Q/A like the RCG and other forums for OpenTX and Taranis, we’d lose any value that we could otherwise add to the OpenTX world. Each author is the moderator of the comments and responses to their work products, and I’ve opted to approve and reply to anything that might help clarify or correct my material. That notwithstanding, if I can provide some immediate help easily, I’ll try to do that. The moderated nature of the comments area also is why our responses frequently are delayed by several hours or even days from the original comments. All of our contributors do this in their spare time that has lots of competition from work and family. So please be patient.

      — In the case of your question about whether there is a video with the answer to your question, I can’t help but suggest that if there is such a video, it’s probably in our very thorough video library that one of our OTXU members spends a lot of time trying to make useful and accessible. So please take a look.

      — With regard to use of the COPY/MOVE command, my assumption in building the class was that if the student actually labored with us through how to add new lines in the Input screen using the Edit feature, then the COPY/MOVE feature that we start using in the Mixer screen would be an easy step for anyone familiar with Windows. So if you’ve really taken the time to work through the information in Inputs, and have actually attempted to add lines in Mixer using COPY/MOVE unsuccessfully, then I need to know what you’ve tried that got bogged down. At that point I’m sure I can troubleshoot your efforts a lot better.

      — With regard to your comment of “mixer screen does not have physical channel assignments yet”, please note in the opening paragraph of the Mixer section that the Mixer “defines how a virtual channel becomes a real radio channel at a specific receiver port”. It sounds like you haven’t yet worked through the information in the Mixer section. Until you’ve configured the Mixer, as described in the instructional material, you shouldn’t expect to be able to set end points in the servo screen. So my recommendation is to restart at the top of Mixer section. If those instructions don’t work for you, please submit a comment describing what step of the instruction isn’t giving you the expected results.

      The whole class that we’re talking about involves working methodically through the material presented in the order presented. It’s not intended to be a shortcut way to get flying. But if you step through it diligently, you’ll get a basic plane set up, and more importantly you’ll know more about how to use OpenTX than most OpenTX users. I know this isn’t what you wanted to hear. Think Tough Love. Hang in there……….. Bob R.

  3. Question,rather than a reply,what does GUV 1 etc mean in the weight option.I get up to 100 then it changes o GUV 1 up to 7 and then -GUV 1 up to -7 .The only way that I can get out is by deleting the line and starting again.

    • I think you must be checking the GV option, which is a “Global Variable” that can be used in the weight field. If you check GV, the adjacent box changes to become a choice list for which global variable you want to use. For purposes of the Basic Airplane Set Up”, we’re not using Global Variables.

      To enter a weight to use in the Mixer, leave the GV box unchecked, and fill in the value that you want used for weight percent in the adjacent box. That adjacent box is a context box that changes what it does based upon what is done with the GV check box. So leave the GV box unchecked and move on to the weight to be used for that line in Mixer. Hope this helps. Thanks…………….. Bob R>

  4. Hello Bob. It is me again.

    You mention here:

    “A negative value for weight in the Mixer will invert the response, but this is not the recommended place to reverse servos.”

    I guess, you prefer INV in SERVO menu!? But it is not mentioned there.

    br Karl

    PS. Thank you for adding those lines …
    If those were the three values in order above, we would multiply 0.75 * 1.00 * 1.30 = 0.975 or 97.5% of the default 512uS for commanded travel to the servo.

    • Thanks Karl — The paragraph you refer to in Mixer is developing the purpose of Mixer weights and I didn’t want to wander too far from that to explore what it isn’t meant for. To help keep the reader oriented, I’ve gone back into that paragraph and inserted a referral on to the Servos and Wrap Up sections where the field for reversing servo travel is explained and emphasized. I’ve also gone back into the details in Inputs and added a remark alerting the reader that servo reversal should not be done with weights in Inputs. Thanks for reading so closely. I appreciate your feedback. Regards…………. R

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