I have an application, like a Polargraph, that has an object suspended on wires, that are connected to motorized spools, located up to 40’ from each other. The motors will be controlled by a Dimension Engineering Sabertooth motor controller by connecting it to a simple joystick via its analog input, and in the mode that allows this to be used to drive a differential drive robot.
My concern is that the two motors will be up to 40 feet from each other. I would also like the user to be perhaps 50’ feet or more in front of the apparatus. So, I have some relatively long cables for robotics.
1st, lets talk about the connection from the joystick to the controller itself. This is an analog signal, with 5v being connected to the top of a potentiometer in the joystick. The other end is connected to ground, and the tap is the control signal, which will vary its voltage. I would think that if this cable is very long, it will tend to pick up some voltages like an antenna. I know those voltages will be VERY low current, but I don’t know how the motor controller will be affected by it. If the cable is simply 3 wires (perhaps two twisted pair wires normally used for Ethernet, with the supply voltage and ground being one pair, and the signal wire, and its other pair being also connected to ground). Would that be appropriate to make this type of control viable? I am trying to avoid a radio control system, and would prefer a wired signal. If the cable to the analog joystick is not a good idea, what would be the simplest alternative method?
The cable going to the motors will be a pair of wires, carrying a pulse-width controlled power. I know that long cable runs act like capacitors, and so a PWM signal will tend to be smoothed out. The PWM could be 5 kHz or 20 kHz. Will the smoothing of the signal over a long cable affect the motor response, or perhaps be a problem for the motor controller?
In thinking how the system will be laid-out. I am currently planning on putting the motor controller near one of the motors. One cable will run to the other motor, and a 2nd cable will run to the analog joystick.
I welcome any comments.
-Joe