How to control throttle by a pot on a transmitter?

Hi all,
I would like to control my throttle value by using a pot on my QX7 transmitter running openTx.

In other words,I want to start a motor on my helicopter with a flip of a switch(motor interlock switch) and when motor starts,i want to control the speed via a pot.But if i flip same switch back(motor interlock switch) motor should stop.

Please suggest if its possible.Thanks.

All you have to do is to assign the pot to channel 3 inside your TX (Typically it is the throttle). It should work. I am personally not familiar with QX7 but channel re assignment is a standard feature in all Tx.

Thanks but if I assign throttle channel to a pot,then how can I use motor interlock by a switch?I am not sure but I think channel override would work.I will try to play with opentx.

You have to provide more information. What FC?

For example using Beta Flight and Beta Flight compatible FC, you can arm the motors using a switch on your tx. So throttle is not used to Arm the motors at all.

Provide more details about your setup maybe we can help you.

Read this thread. Its got your answer Motor arm/disarm with a radio switch

I don’t think you can do this using Ardupilot FC.

You can do this a number of ways. The precise use case will help guide a decision on what is best for you. Can you elaborate a bit more?

You do not want to do this. Channel 3 in tradheli is the collective control not the throttle. Throttle control is done with the RC channel assigned to the motor interlock. You would only be able to control throttle if the H_RSC_MODE is set to 1 which is the passthrough option. So you would have to use some feature in your TX to do that but I do NOT recommend the passthrough option on the RSC (rotor speed controller).
Pleas elaborate on what you are trying to accomplish by being able to adjust the throttle directly.
Also here is the wiki that describes the RSC in more detail.
RSC wiki

bnsgeyer Thanks for explanation. I have no experience with heli so I was applying my RC plane knowledge :slight_smile: My bad.

ninja_zx11 has to provide more details as he is the one who posted this question.

No worries. I just wanted to make sure @ninja_zx11 did not try that. The heli set up is quite different from even multi’s.

I would still like to know why @ninja_zx11 wants to control throttle directly. That way I could better help choose the right RSC mode. There are some pitfalls with the passthrough RSC mode with guided or auto flight modes.

Hi all,

Sorry couldn’t reply earlier.

I have a 3 position switch assigned to motor interlock on my 450 helicopter.So in middle position,motor runs at ~60% throttle and at 3rd position it runs at full(i think).This is the first time i am setting arducopter on my heli and recently i had a crash which was related to IMU (MPU6000 on OmnibusF4V3).So now i am rebuilding my heli and i would like to start with low head speed just to get a feel of stabilized mode.That’s the reason i want controllable rpms.For now i won’t be doing any auto missions.Just Acro,stablized and position hold using gps and compass.

Before installing arducopter, my heli was flying okay on the blade’s recommended throttle and pitch curves.

So unfortunately, ardupilot isn’t setup to enable the user to easily move between throttle and pitch curves in flight. Effectively there are two pitch curves if you want to call them that. One is in acro flight mode which is the full pitch throw defined by H_COL_MIN and H_COL_MAX. The other is in stabilize flight mode as a subset as defined by the IM_STB_COL Params. You can read up on the RSC modes. If the throttle curve is a flat line at 60% then you can just as easily use mode 2. I assume this is an electric motor with an ESC that will ramp up the throttle to the set value. When you are ready to change speeds then go into the param for H_RSC_SETPOINT and change it there. You will have to land and shutdown unless you have someone that is able to send the parameter change using mission planner or QGC while you are flying.

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Thanks Bill.Yes its an electric Blade450 3D with flybars.I will definetly read more about RSC modes.I also need to make sure to use proper mode so that motor doesn’t shut down if receiver failsafe occurs.