This is a completely working PWM modulator. It was designed to minimize costs. 555 - 10ct;diode - 1ct;1nF ceramic capacitor - 1ct;potentiometer - 15ct. So this whole circuit costs only around 27 cents.
A problem is the variating power consumption, but I will try to fix that. Also, you can not turn it on and off completely, only like 99% on or off.
