Hi!
I´m controlling successfully two DC motors with “Sabertooth Dual 5A 6-12v regenerative motor driver” and I´m trying to make the speed range adjustable. PWM connected between motor output and motor did nothing and potentiometer connected between analog joystick outputs and signal inputs just messes up everything.
I´ve tried to put signal, voltage and ground all in the same inputs (I´m referring to potentiometer for the knob and the joystick) with no success. Carrying voltage through potentiometer side pin to middle pin and the same to joystick but middle pin to signal input with and without the third pin grounded did some weird stuff. With ground wired or not, both motors just start moving on their own (in this case adjuster makes them stop or move faster and joystick does nothing) or the adjuster potentiometer mixes the directions without reducing the speed and joystick works like controlling angles had been twisted 45 degrees. So if you pull joystick handle straight up, it launches both motors and pulling it between up and right only one of the motors will run.
How can I adjust the motor speed range without messing everything up? If the motor driver makes the stalling point at 2,5v, full reverse 0v and full speed 5v, how on earth this method could ever work? This additional potentiometer should lower top voltage and increase lowest possible voltage at the same time?
Before many any additional connections, please provide a list of the parts you have and what you hope to to.
It sounds like you want to use the Sabertooth by controlling it using a joystick which is physically wired to the analog inputs.
A joystick normally has two 3-pin potentiometers: you need to wire both GND pins to the GND on the Sabertooth, and both V pins to the V pin on the Sabertooth.
The center pin (wiper) of each potentiometer is connected to each of the analog pins on the Sabertooth. Note that if you find the joystick is 90 degrees to the way you want it, simply swap the pins.
You then need to carefully follow the DIP switch configuration in order to set up the controller correctly (do you want mixing mode?)
I´m using Sabertooth motor controller as described above, both motors are yours, product code (RB-Cyt-32). Joystick I´m using is from you also, product code (RB-Sct-283).
Controlling these two motors with joystick is functioning perfectly. Directions and the wiring is ok. Problem is how to reduce the maximum speed of these two motors, with adjustable control? I tried to describe in my earlier post what have I tried so far to get it work. I think it should be possible with potentiometer somehow, but I cant figure it out on my own no matter how many hours I try to make it work.
When I said the potentiometer makes the joystick control go “like its 45 degrees twisted” I really meant 45 degrees, not 90.
I´m not a professional and I understand just the basics of electronics. Your products are working perfectly, your customer service makes an excellent example for others in the business. If you would advice me with this problem also, it would be incredible. Either way, I will recommend you to everyone I possibly can. I´m just ready to pull all my hair off at this point, I´m kind of desperate here…
You essentially need to lower the input voltage, so the output voltage (which affects the speed) decreases as well. This can be done using a resistor (one for each potentiometer). You’d need to calculate the right resistor value.
So, I need to reduce input voltage (12v) for the motor driver board? I didn’t use resistors for this, because I want the speed range to be easily adjustable.
Do I mess up the sabertooth motor driver if I adjust the voltage while its running?
Not quite. The motor controller has three sets of pins:
- One for the main battery (which you connect directly)
- One for the left channel (GND, 5V, Analog Signal)
- One for the right channel (GND, 5V, AnalogSignal)
The controller provides 5V to the potentiometer, and the potentiometer returns anywhere between 0V and 5V, with 2.5V being “neutral”. 0V represents full speed in one direction, and 5V represents full speed in the other direction.
If you don’t want full speed, you’ll need to restrict the maximum and minimum voltage which the potentiometer can provide around 2.5V (for example instead of 0 to 5V, the range should be 1 to 4V, keeping 2.5V as "stopped).
The voltage essentially needs to be mapped from 0-5V to say, 1-4V keeping 2.5 as mid-point. A sample circuit and explanation here.
This is exactly what I´m looking for and what I tried to explain in my first post. I´m just not after permanent changes in the max.speed reduction, in that case I would pick another motor with less RPM or play with the spur gear sizes. The adjustment should happen by just turning a knob or similar to that.
Are you saying that this adjuster is not possible to make with just wiring two extra potentiometers with joystick and motor controller?
We know what you want to be able to do: Adjust the maximum speed (in either direction) ideally using potentiometers, though honestly not sure if this can be done while also keeping the “center voltage” at 2.5V.
From what we can see, you seem to have a good idea of what you want to do and how to wire it, but it’s just not giving the results you expect? Can you provide a schematic?
The link in the last reply uses a small circuit which will work, but is not adjustable.
