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):