I’m into RC, and I need a controller for rc tanks. You know, I need one stick to control the thrust (forward, stop, reverse proportionally) and steering by using another stick, as in a rc boat or car.
As far as I can understand, the TreX Dual Motor Controller should work, but I have some doubts, and I need to clear them before ordering.
Does it work the way I need it to work? It should work as the volume and balance controls in an audio amplifier: with the balance centered, both channels receive the same audio level, if I turn the balance half the travel to the left, the left speaker should sound half the volume, without altering the right one, and so (just an example ignoring the logarithmic response of an audio potentiometer and all of that!).
If the volume is set to 0 (zero) no matter what I do with the balance pot, nothing happens.
Well, I hope I was clear, the transmitter has two sticks, the left one travels forward and reverse, it would be the thrust, the left stick is the steering, it travels from left to right.
Is the TReX compatible with RC channels signal (pulses, ranging from 1 to 2 ms)?
Yes, the TReX can do what you need. When in RC mode, it responds to standard RC hobby servo pulses, and when it is in mixing mode, channel 1 controls steering and channel 2 controls throttle (with mixing disabled, channel 1 controls motor 1 and channel 2 controls motor 2). Specifically:
motor 1 speed = channel 2 + channel 1
motor 2 speed = channel 2 - channel 1
So if channel 1 is at neutral, both motors will turn at the same speed as determined by channel 2. If channel 2 is at neutral, both motors will turn in opposite directions at speed determined by channel 1, and the tank will spin in place. Note that the user’s guide for the TReX is available under the resources tab of the product page if you want to understand how it works in more detail.
You can also accomplish what you want using our newer Simple Motor Controllers. They have some features that the TReX does not (and vice versa), and I think they can sometimes be a little easier to use because they can be configured from your computer via USB using the Simple Motor Control Center software. Each SMC can only control a single motor, but they can be paired to enabled mixed control of two motors (i.e. they can work the same way as the TReX with mixing mode enabled). Section 4.3 of the user’s guide has more information about this.
As for the simple motor controllers, due to costs it’s worth buying one dual motor controller. I saw the video of the chassis with the caterpillar running with the dual controller and it looks as the solution I need for my tanks.
Currently I use twin ESC’s (electronic speed controllers) one for every channel but it’s not easy to control the vehicle that way, I’d prefer the “classic” way, i.e., left stick is the throttle, right stick for steering.
A question about this:
“
motor 1 speed = channel 2 + channel 1
motor 2 speed = channel 2 - channel 1
So if channel 1 is at neutral, both motors will turn at the same speed as determined by channel 2. If channel 2 is at neutral, both motors will turn in opposite directions at speed determined by channel 1, and the tank will spin in place
”
So, to spin, I just need to move the steering stick on the transmitter, right? Now, if I push the throttle forward, the vehicle moves straight, then I gently move the steering stick to the left (engaged to the channel 2 of the dual controller) will it gently move while turning to the left?
Using a dual motor controller can be more convenient from a wiring perspective, but it is not necessarily cheaper. The Simple Motor Controller 18v15 is the most comparable to the TReX in terms of voltage range and output current, and a pair of them is less expensive than a single TReX. Two SMC 18v7s provide a good solution if you need something between the TReX and TReX Jr.
The channel mixing combines the individually controlled throttle and steering components. You can see this for yourself by trying out a few more example cases. Let’s say you put the throttle at speed +5 and steering at speed 0. In this case, both motors will turn at speed 5 and the tank will drive forward at speed 5. If you then start to apply steering, you will decrease the speed of one motor while increasing the speed of the other, but this speed difference is still adjusted by your throttle’s +5 to each motor. So when the steering speed is 3, the left motor becomes 8 and the right motor becomes 2, which is an arcing curve rather than turning in place.
OOPS that is not what I’m looking for, that’s not a true steering system: If I start to apply steering, one of the motors will hav its speed decreased while the other one will shouldn’t have its speed increased.
I’m not sure what you mean by a “true steering system”, but note that the system you describe does not let the tank spin in place when using the steering stick with the throttle at neutral (in fact, the tank wouldn’t respond at all to steering when throttle is at neutral because you only want the steering behavior to allow the motors to slow down, and there is no room for them to slow down any further when they are not moving), so that is probably not what you really want. Consider how you want the motor speeds to behave in the two cases described by throttle=0 and steering=0. The most intuitive control will then arise from the sum of those two behaviors, which is what the TReX and Simple Motor Controllers do (as well as all other controllers I know of that support channel mixing).
“you only want the steering behavior to allow the motors to slow down, and there is no room for them to slow down any further when they are not moving”
Well that’s EXACTLY what I need, that the steering system only decreases the output to the left or right motor, according to where I want to steer, to the left or to the right.
I am not familiar with any controllers that offer that kind of mixing, but I’d be interested to hear about it if you find one. Can you elaborate on why you need this particular behavior?
Just to be clear, do you understand my point that when using a mixing system like the one you describe, the steering stick will have no effect when the throttle is in neutral, and that you will never be able to make the tank spin in place because you can never have your two motors spinning in opposite directions? I’m still skeptical that you actually want/need this kind of mixing, especially given this line from an earlier post of yours:
Spinning in place based on input from the steering stick is not consistent with a steering system that “only decreases the output to the left or right motor”. The best you would be able to do is spin about one of your treads by having one motor turning and the other stationary.
Also, you don’t have to quote my entire posts in your responses to me; if your post comes right after mine, I’ll assume you are responding to that particular post.
“do you understand my point that when using a mixing system like the one you describe, the steering stick will have no effect when the throttle is in neutral, and that you will never be able to make the tank spin in place because you can never have your two motors spinning in opposite directions?”
Yes I clearly understand that, the streering system just has to take what comes form the throttle and decrease it proportionally for the motor of the left or right. I too understand that I can’t spin with that conditions but that’s not the problem (by braking one track and movint the other one, some kind of spin can be achieved anyway).
A steering system that “only decreases the output to the left or right motor” is exactly what I need.
Let me please quote your words:
“The channel mixing combines the individually controlled throttle and steering components. You can see this for yourself by trying out a few more example cases. Let’s say you put the throttle at speed +5 and steering at speed 0. In this case, both motors will turn at speed 5 and the tank will drive forward at speed 5. If you then start to apply steering, you will decrease the speed of one motor while increasing the speed of the other, but this speed difference is still adjusted by your throttle’s +5 to each motor. So when the steering speed is 3, the left motor becomes 8 and the right motor becomes 2, which is an arcing curve rather than turning in place.”
The line in bold refers to that behavior that I don’t’ want, but it seems that the TReX does just that.
I might be able to suggest some sort of solution if you could explain why you need this particular behavior. As I said in my previous post, I am not aware of any other controllers out there that behave this way, but I’d be interested to hear about it if you find one.
I have been using the TReX dual motor controller for 10 weeks. it was connected to the rs-232 port`s of wireless system and the connectors at the left side of the controller were produced the power of wireless system. jumpers: mix jumper was active ,BEC jumper was active, mode select jumper was not connected and learning mode jumper was not connected . 12Volts constant dc was connected to the input during this period. i had constant 5V dc at two first pins of Rc Chanel inputs it was fully under control and i had no problem with it.
but now i have no voltage at RC input pins or near 0.24V and when i test the short circuit the first two pins or most two left pins are short circuit.
