The following is a schematic diagram of a lamp brightness control. Lamp used is a light tube with a voltage 3V. You can replace the lamp with other lamp types, such as LEDs.
How the circuit works:
IC1 works to generate 150Hz square wave which having a variable duty-cycle. When potensiometer P1 is fully rotated towards D1, the output positive pulses appearing at pin 3 of IC1 are very narrow. Lamp LP1, driven by Q1, is off as the voltage across its leads is too low. When potensiometer P1 is rotated towards R2, the output pulses increase in width, reaching their maximum amplitude when the potentiometer is rotated fully clockwise. In this way the lamp reaches its full brightness.
The lamp LP1 could be one or more 1.5V bulbs wired in parallel. Maximum total output current allowed is about 1A.
R2 limits the output voltage, measured across LP1 leads, to 1.5V. Its actual value is dependent on the total current drawn by the bulb(s) and should be set at full load in order to obtain about 1.5V across the bulb(s) leads when potensiometer P1 is rotated fully clockwise.
Circuit source: redcircuits.com
