Yes, this is going to be problematic:
- you want to use twisted pair. To make any use of twisted pair, you'll need to drive it differentially. You don't have a differential driver! Your 555 output is single ended.
- A 555's drive strength isn't great – so your gate signal's edges aren't incredibly steep (depending on gate capacitance) even without longer transmission line between. With transmission line, you will experience dispersion of the signal, and that leads to slower edge, meaning the MOSFET turns off and on slower, and that means it's longer in "half on" mode, which means it gets hotter. This is very undesirable. You will need to implement a "edge steepening" gate driver / line receiver to solve that.
- Since you should be using differential signalling over twisted pair anyways, a differential receiver with some kind of Schmitt-trigger input behaviour would be desirable anyways.
- Correlated with why you would want differential signalling: your MOSFET assumes identical ground potential as GND on the 555. Nope! That is usually not the case for motors in other places than the controller. Can't rely on that. You will need a differential receiver, a gate drive for your MOSFET that refers to local ground there, and gets its power locally.
Generally, the idea of transmitting a high-frequency signal (your PWM has very high frequency content – many times the switching frequency, because you need your PWM edges to be sharp, and not nice and sinusoidal!) over a long distance is a bit … bad. Instead, just communicate the PWM duty cycle you want (which changes much slower, necessarily!), and generate the PWM at the motor. Much easier!
Together with:
- The 555 is a rather bad source for PWM anyways. I'm not sure why you'd ever want one to control a motor – the cheapest microcontroller can more flexibly, more reliably and easier to adjust create better PWM control.
Really, this calls for a microcontroller driving the MOSFET close to the motor, and a separate microcontroller controlling that microcontroller over a digital bus that's adequate for your distance and environment (and that bus might run very possibly be transported over twisted pair – or something else, again, depending on your distance and environment).
