Control speed of a DC motor

[PaulE]

Dear users,

What is the best way to control the speed of a DC motor? I've tried to control both a PC fan and a DC motor from a game to be controlled by an Arduino board.
What I did was hook a 12V power source to a TIP122 and use analogWrite on pin 6 (using Arduino NANO) to control the input.
This used to work for a RGB led strip to control its color, but for some reason when I put a lower value than 255 the motor either doesn't run at all or makes a buzzing noise.

I don't know much about electronics and I think I'm totally doing something wrong, but I don't know what.
Hopefully any of you can send me into the right directions

[MarkT]

Which motor?  what current does it take?  What 12V power source?  How much current
can it provide?  How have you wired the TIP122?  Do you have a flyback diode?

[RMurphy195]

I found this article in the Arduino playground - does it help? http://playground.arduino.cc/Main/DCMotorControl#.UxzZtYWf7Sg

Or maybe this http://www.jeremyblum.com/2011/01/31/arduino-tutorial-5-motors-and-transistors/

[RMurphy195]

I received this via my email this morning.

Not sure what jremington is getting at, assuming the mail is genuine. Explanation please jremington, as to what it means , in what way it is supposed to help point the OP in the right direction, and why you feel the need to be unpleasant?

Cheers - Richard

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I found this article in the Arduino playground - does it help?
We don't need help -- you do, and a good start would be to answer the questions in reply #1 as carefully as you can.

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[pwillard]

I think he thought you were OP...

The email is very clear about what is needed "from OP" and to me... not "unpleasant" as you say.

OP   Please answer the questions... or we won't know enough to assist.