PWM LED DIMMER
This is a circuit that can control the brightness of the led efficiently unlike the lm317 circuit which would waste the unused power for the led as heat. The circuit is a oscillator circuit created by the 555 timer chip which would turn the n-channel mosfet on and off, referencing to ground each time it turns on. the brightness of the led changes depending on the on and off time of the pwm signal, The on and off time is called the duty cycle. if the the duration of the on time is longer than the off time, the led is brighter, but if the duration of off time is longer the the on time, the led gets dimmer. In the circuit, you can change the pwm duty cycle by turning the 50k ohm potentiometer clockwise or counter-clockwise. Be sure that that the power voltage isn't higher than the led(s) forward voltage. If it is higher it would blow out the led, because if you turn the potentiometer all the way to one side where there is more on time than off time duty cycle, the voltage of the input would fully go to the output side.
If you replace the led(s) with a motor, then this circuit can also control the speed of a small motor, or a large motor, if you put a heat-sink on the mosfet.
(You can use any high power n-channel mosfet)
The 555 timer does make a voltage drop from the input to the output voltage.
Below you can see the pin-outs of the symbol in the circuit.
