Temperature-controlled servo

I was visiting Jämi airfield here in Finland today for some scale-airplane eye-candy. One of the pilots there asked if I knew a way to make a servo temperature controlled, he wanted tomake cooling flaps on his warbird’s cowling temperature controlled.

Never thought of that but since it is Jeti we are talking about it should be not only doable but also easy. So, we opened a test model in his radio and tried, sure enough, it was easy, here’s a quick how-to just so we won’t forget.

Create a telemetry control

We all know telemetry controls, right? They can be used as proportional also and it is this that comes handy here.


Use a temperature sensor and make the control to “Proportional”. After that give the limits in the “Range”-section. Now, there are three values, think of it like “in what temperature would you like the servo to be in minimum position”, this is the lower value in range. Next is the middle value, answer the question “in what temperature would you like the servo to be in the middle”, and last of course the high value, “in what temperature would you like the servo to be fully open”.

The filtering in this case means smoothing of values, basically the bigger value the smoother response but also slower response. This can be left on “1” here since temperature-sensor very rarely “jumps”.

Also put the default value to -100% to keep the servo “closed” after initialization.

Function assignment

Add new function to your model and choose the newly created telemetry control as the control:


Of course you need to assign the function to a servo (or servos):


Since this is now automatically adjusting make sure to adjust servo limits etc in servo setup:


And basically you’re done. For testing, as always, you can assign a 3-position switch to function while adjusting servo limits etc. Cooling and heating the sensor might be to much of a hazzle.

Some pointers

The controlled servo can be mixed to your liking, however the created telemetry control cannot be used in mixing, unfortunately. For example a scenario where we have cooling vents manually opened could be mixed with created telemetry control for safety. Well, ok, we can achieve this via some sequencers etc but why make it difficult when this is so easy?

Have a nice day in the field!

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