The power adjustment pulse width is a method in which a control device works as a switch that opens and closes many times per second. Switching is so fast that our eyes do not see the flashing (due to the persistence of the retina). However, that manages the device and adjust the power modifying the average between driving time and which is open ("duty cycle").
For a good system of dimmer by pulse width you need to add a pair of diodes as we can see in the figure. These diodes cause, according to the position of the potentiometer, the 100nF capacitor charge and discharge at different speeds by modifying the aforementioned "duty cycle". With the values shown, the oscillation frequency is approximately 3 KHz. This frequency can be modified by changing the value of the potentiometer or 100 nF capacitor.
1 1/8 Watt resistor 1,8K
1 10K resistor 1/8 Watt
1 Potentiometer 10K (see text)
1 disk or polyester capacitor 100 nF (0,1uF)
1 disk or polyester capacitor 10 nF (0,01uF)
Electrolytic capacitor of 47uF 1 25V
2 1N4148 diodes (or 1N914)
1 yellow LED
1 type N-channel mosfet IRF530 (you can use any N-channel MOSFET power encapsulated TO220)
1 Integrated NE555 circuit (or equivalent 555)
1 connector to terminal 3 way
Few who want to control a strip of multicolored LEDs, in the following figure you can see the wiring needed using three identical systems to the one described in this article. They can mount individual heat sinks or one to three MOSFET. In the latter case I remind you that it is necessary to isolate each other that the metal bodies of the MOSFETs are connected internally to the "D" terminal.