I'm making my own motor control board because I've yet to find one feasible for my project. I need 10 DC motors, need them to operate very slowly and to withstand around 1-4 lbs of weight. What motor would be best and what potentiometer would be able to control these motors?
To get the rotation speed and the torque needed for your project, look at various combination of motors and speed reducing gear boxes. Find some that fit you specific requirements and then select those that meet your power supply requirements.
In the mean time. figure out what you really mean by being able to withstang 1-4 lbs of weight. Motors and weight do not compute together.
Look for a "gear motor" (a motor with an attached gear mechanism). DC motors tend to run at high speed and gearing-down trades-off speed for torque. Assuming you need to lift 4 LBS, it's easy to calculate the required torque, depending on the pulley diameter.
As a rule, everything should be "over rated". You should probably choose a gear motor with at least twice the calculated torque. You don't want to be pushing things to the limit. Same thing with your motor driver. Get a motor driver and power supply that can supply more current than you need. (But don't apply excess voltage to the motor.)
Does the pot control speed? Any linear potentiometer will work as input to the Arduino. 10K is pretty common. If the resistance is too high it's more prone to noise pickup and if it's tool low it will waste power and it can even overheat, but that's not going to happen with 5V and 1K or higher.
The Analog Read Serial Example shows you how to read a pot.
If it doesn't have to be reversable MOSFET drivers will work with analogWrite() which is PWM and MUCH BETTER than true analog in this application.
If it has to be reversible, you'll need a "H-Drivers", and you probably don't want to build them yourself, especially since you are asking these basic questions.
If you don't need speed control you can use relays. Relays are electrically-operated and electrically-isolated switches so they are pretty simple. But the Arduino can't directly drive a relay coil, so you also need relay drivers, or "relay boards" with a built-in driver circuit are super common.
Thank you so much for the detailed response.
Unfortunately, I'm turning 4 lbs, think of a small 4lb weight plate on the motor. Does your information still qualify?
How is this weight supported? Very few motors have built-in thrust bearings, but you can get or make gear boxes with thrust bearings.