Control Chain Takeaways (What Goes Where)

We’ve worked hard and learned a lot about the basic command chain of OpenTx on the Taranis.  Let’s step back from the details for a moment to consider how to use what we’ve covered.  Then we’ll make a brief stop in Telemetry before we wrap up and get our model flying.

In the Inputs screen we configured the control variations that each individual input will carry.  In the Mixer screen we considered how those configured inputs are combined and directed to a receiver port.  In the servo screen we planned how the servos respond to incoming control commands.  The power of OpenTX comes from its great flexibility to let you achieve exactly what you want.  Along with that flexibility comes the potential for confusion and a premium on having a consistent approach that exploits the structure of the system.   Here’s a recommendation that ties it together:

  • Use the Inputs screen to manage variations within an individual control, such as switched high/low rates and expo on an aileron.  The maximum weight allowed in Inputs is 100% (regardless of Extended Rates).  Use that for your highest rate setting on each input, and set the reduced rates in relation to the 100% high rate.  Note that the one-sided stick option allows you to treat each side of a gimbal stick as a separate input if you need it.


  • Use the Mixer to manage variations among different controls, such as adding a portion of the flap deployment signal into the elevator channel to avoid ballooning, or correcting roll and pitch coupling in knife edge by increasing or decreasing aileron and elevator based on the rudder input.  The combinations are unlimited.


  • The weight in a given Mixer output channel is the product of the incoming weight from Inputs times the weight applied in that mixer line.  The weight applied in a mixer line can be up to 500% to correctly blend the relative amounts in a channel and allow for an input with a small value.  Net Mixer outputs exceeding 100% are stopped, or clipped, at 100% to become the input to the servos.


  • Set servo travel direction in the Servos screen.  With trimmers zero’d on the Tx, set sub-trim amounts for each channel in the Servos screen to center that control surface.  If large sub-trims seem to be needed to center control surfaces, take a look at re-working the mechanical linkage.


  • Edit the servo travel limits for each gimbal side in a channel line in the Servos screen to achieve the desired deflection for hi rates on that control surface using Extended Limits if necessary.

Different users have different preferences for the order in which to complete Inputs, Mixer, and Servo screens and use the Inputs, Mixer, and Servos capabilities in different ways.  The material we’ve covered is the approach I’ve found that makes sense to use the features of OpenTx.  It’s also easily explained to others, and it works consistently and is easily maintained.  If you use a plan that exploits the control chain, you’ll do well.  If you follow that plan consistently, you’ll find that OpenTX becomes a helpful information and planning manager in achieving your results.   Otherwise, OpenTX can become a growing source of frustration to achieving your goals from one model to the next.

Enough philosophy.  The finish line approaches — Let’s roll!


Control Chain Takeaways (What Goes Where) — 2 Comments

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