Modify a 2 channel 2 motor receiver to 1 motor 1 rudder

[poulsbobill]

I have a Firebird Outlaw, (2 motor "rudder" is controlled by varying the input to each motor- tx has 2 sticks -one throttle one "rudder"- proportional). I want to use the electronics to power a 1 motor 1 rudder set-up. In other words i am trying to hook up one of the motor controls to work as a rudder . It would work to turn the rudder one way...but i want left/right by way of a servo or actuator ...have you guys ever seen this done? And if so how?

Thanks

Bill

[rjet]

I have done it the other way around and built a transistor mixer for a standard radio to be used with a two motor differential thrust, but it sounds like you want it the other way around.

It would be more difficult to do with analog circuits, so you would probably want to program a microcontroller to measure the pulse width difference between the two channels and regenerate a signal for a rudder servo.

[poulsbobill]

Is their not a way to bypass the 2nd stick (rudder control) on the reciever board? in other words get to the output on the board where it is seperate from the throttle control. (you have to forgive my naivete here).

[darkith]

I suspect the complexity of doing this would far outweight the cost of a cheap proper 2/3/4 ch radio system.

Like rjet, I can only think of these two approaches:
1. Microcontroller measuring either the analog signal before the motor drivers, or off the motor drivers.
2. Analog system driven off motor drivers. Off the cuff, something like feeding both outputs through a pair of diodes to driver a motor FET, so when power is sent to either of the "virtual" motors, the main motor is on. Also feed the "virtual" motor driver outputs to a H-bridge of some sort, so when there's a differential between them, it drives an actuator (or motor-based actuator) to one side or the other.

Ewww. Hack-n-slash.

D.

[poulsbobill]

Thank You both for the info...you are probably right about the time and expense. Was just a thought. Did think i could do the existing setup with one set of wires to the motor and the other set to the rudder actuator set with a permanent right turn and then adding "rudder" would turn it left.

Ok your right i'll spring for the new rx, lol ...thank you again

Bill

[jkmadsci]

i suppose you could use a pic chip to monitor the two motor drivers.
The output to the new motor would be sticka plus stickb
The output to the rudder servo would be equal to sticka minus stickb


Another words the pic chip would have to monitor the voltage going to both motors and calculate new motor voltage(pwm), and control another with typical servo pulse widths.