2Pcs PWM Fan Speed Controller,4 Wires 0-5V 12V Fan Speed Controller PWM Speed On
The PWM frequency is 25KHz, which matches most 12V adjustable speed fans on the market. 1 pin is grounded, 2 pin is connected to 12V, and 3 pin is left empty. The duty cycle is adjustable from 0% to 97%, and the speed regulation range is wide.