Also a good starting point for novices wanting to get their hands dirty with the 555 timer IC. Some would argue that this is not the most efficient approach, but hey (read the title), it's simple, and it works.
Check the video out.
More images and description here.
Pulse Width Modulation (PWM)
Put simply PWM is the process of switching power ON and OFF to a device in pulses at a specific frequency. Same approach used in commercial light dimmers, DC motor speed controller, CPU fan speed controllers and etc.
That's what we seek to achieve here.
Step 1: Part List
1) 555 timer IC - 1
2) 100K variable resistor - 1
3) 1N4148 Diode - 2
4) 100nF capacitor - 2
The 555 Timer IC
The 555 timer is arguably one of the most popular IC ever made. There are thousands of resources online if you're interested to delve deeper into the subject. I'm just going to give the simple description directly relevant to the build
PIN 1 - Ground
PIN 2 - Trigger
When LOW, it causes the Output pin to go HIGH. Activated when voltage fall
below 1/3 of +V.
PIN 3 - Output
Output is HIGH when Trigger pin is LOW. Output is LOW when Threshold pin is
HIGH. Output is LOW when reset pin is LOW.Output pin is able to source or sink
PIN 4 - Reset
Short to +V when not in use.
PIN 5 - Control Voltage
Grounded through a capacitor when not in use.
PIN 6 - Threshold
When voltage reaches 2/3 of +V, this pin will cause Output to be driven LOW.
PIN 7 - Discharge
Grounded when Output pin goes HIGH.
PIN 8 - +V