How to wire this PID controller and PWM controller

Hi All,

I'm a mechanics and very weak at the electronics side,

I want to build a roller that turns in very consistant low speed with high torque for over 24 hours.

I have got a PWM controller with digital display module connected to a 12V DC motor.

But I've realized that the motor is reducing speed at really low rate over time.

I want to somehow connect the existing system with a PID controller of some sort that enables the motor to turn and keep its speed at a very consistant rate over long period of time.
This motor may need to turn for over 24 hours.

Here I have the following items from ebay, hope to put these bits together to achieve what I want.

1. PID controller
2. PWM motor controller
3. High torque 12V DC motor
4. 12V 20A power supply









Please help, I sense that this project is very near completion.
The only last thing that I need to tackle is this speed consistancy issue.

Please share your knowledge.

Thanks very much