DC motor control over long wire (100 m)

[eluminer]

Hello guys!

I'm working on a project. Now, what I need is rather simple. I have to be able to control the speed of a DC motor over 100m (300ft) long twisted pair (1 pair from Cat 5 UTP cable).
What I'm looking for is more or less "plug and play" solution. So, I would like if someone can point me to components (motor controller etc.) that I would have to use in order to achieve this - as simple as possible. This would be used for professional application so quality solution is required. I would like to avoid too much programming, PCB building etc.

So, idea is that a have a potentiometer (or some form of control - PC can work too) on point A. On point B, which is 100 m away, I have a DC motor and power for it (battery). In between goes 100 m long twisted pair. So, only signal is transferred over wire, not power.

I've seen couple of potential solutions, but it seems that this is relatively simple request so I don't want to overcomplicate this by using some unnecessary complex solutions. Motor won't pull more than 20A at 12V.

Budget: I would like to stay under 300$ without motors, PC (if necessary) and cable. So, only controller(s), interface or whatever.

I actually need to control 2 motors individually, but I also have 2 pairs at disposal. If this is doable over 1 pair, that's even better.

Please help!

Thank you!

 

[FvM]

12V/20A is well in the range of electro flight motor controllers. They are mostly equipped with standard remote control receiver PWM signal inputs.

You can either send PWM control over remote line, or use a digital protocol that's converted to PWM by a microcontroller.

 

[eluminer]

OK, that is something that I had in mind (I'm in multirotors so I know something about this).

However, lets say that I have a brushed DC motor and brushed ESC that has standard servo connection (3 wires). In "RC world" I would use RC receiver and transmitter. But what peace of hardware should I use to send signal to that ESC over 100 m long wire(s) and what should I use for input? I suppose I can't just run 100 m long servo wire without problem, right? Can PWM signal travel over 100 m without problem?

In short, I don't really need theory behind this, I need end solution which you think will work. You know, buy this, plug this in that and done! Doesn't really need to be that simple, but you get the point.

 

[FvM]

A RC pwm signal is basically a slow digital signal and can be transmitted through any suitable digital IO standard, e.g. RS-485. To save a second twisted pair, the signal can be transmitted as serial UART signal through RS-485 and decoded to PWM at the receiver side. I guess that the sender won't primarly generate PWM signals, so there must be an encoder somewhere in the system. Translating e.g. analog signals (speed potentiometers) to serial data and back to PWM can be both done by small microcontrollers, any type of your choice like PIC, AVR, ARM...

In bygone days, we combined multi remote control channels by time multiplex into a single signal using a discrete circuit or some simple ICs. Of course these means are still to your disposal today.

 

[eluminer]

So, lets say I have some DC motor and this ESC:
https://www.hobbyking.com/hobbyking/store/__6468__Turnigy_30A_BRUSHED_ESC.html
Can you put links to components that you would use to control this motor (or two independently) over twisted pair. So, micro-controllers, potentiometers etc.

Thank you very much.

 

[kripacharya]

current loop comes to mind. Or differential pair... any of many methods.

 

[FvM]

Can you put links to components that you would use to control this motor (or two independently) over twisted pair. So, micro-controllers, potentiometers etc.

I keep my previous comment that effectively any microcontroller can do it. Analog inputs to read potentiometers are probably the most specific requirement, and a serial UART if you want to use a serial protocol over the long line (recommended for robust operation, I think).

Most people would choose a microcontroller that they already used for other applications, so they can quickly start a new project.