DC motor to control just 1 speed, please!

Hello, I am working on a project. I have a 12 volt 9 Amp DC motor that gives 60rpm at 12V, I already bought a power supply, and I have my Arduino board.
I would like to control the speed to 60rpm, but I believe I need something else than just controlling voltage in case of the different weight applied to the motor or different conditions.
Any suggestions? Please! I am not that familiar with electronics and I have been searching online for a solution for about 2 months and I seem to get more confused eveytime. I do NOT need to change direction or change speeds, just the 60 rpm’s.
Can someone tell me what to do? I would really really appreciate it, I am really desperate :frowning:
Thank you very much!

You could use PWM to control a large MOSFET which could control the speed. You need to determine the rotation speed of the motor, so that may be a more complex part of the project. This and the old forum may have post about tachometers that possibly could be helpful.

Hello! Thank you for replying, but it is not that clear to me do I use PWM or should I keep looking? Also you said that PWM is complex or the MOSFET?

PWM is simple, as is controlling a motor, see:- http://www.thebox.myzen.co.uk/Workshop/Motors_1.html and http://www.thebox.myzen.co.uk/Workshop/Motors_2.html