I recently bought a nice looking regular light bulb, commonly refered to as "Edison bulb".

I was hoping to find a way to dim the light, so you could just see the filament glowing. Having zero knowledge of electronics, I started looking for a dimmer to put in a simple electronic circuit.

However, if I try to find answers to how to achieve this, I only find LED-related questions. Furthermore someone told me about a difference between a dimmer that dims the light, but eats up the same amount of power as when the light is not dimmed?

I guess these are really basic things for someone with knowledge of electronics, but any help would be a huge step forward for me.

  • \$\begingroup\$ Since you have little knowledge of the subject, I highly recommend against you building anything yourself. The voltage and current produced from your mains outlet is highly dangerous and can easly kill you or start a fire! I'd recommend using a simple off-the-shelf dimmer switch. \$\endgroup\$
    – DoxyLover
    Commented Sep 17, 2015 at 10:31

2 Answers 2


You can dim a light bulb two ways - decrease the current or decrease the duty cycle of the source waveform.

If you put a resistor (or potentiometer) in series with the bulb, the current will be decreased accordingly. The bulb filament will not heat up as much, and will dim. This is a huge waist of energy, because the resistor will use a lot of power in the form of heat as a result of reducing the current.

If you decrease the duty cycle of the source waveform, the average current will drop and cause the same reaction. How much power is saved depends on the circuit used to control the duty cycle. Look up triac.


The easiest way to dim a regular (incandescent) bulb is to use a triac. They do not eat more power when the bulb is dim and an assembly using them (full dimmer) can be easily purchased.

Here is an example http://www.homedepot.com/p/Leviton-Trimatron-600-Watt-3-Way-Incandescent-Rotary-Dimmer-White-R62-06683-0IW/202077656

or http://www.homedepot.com/p/Leviton-300-Watt-Incandescent-CFL-LED-Tabletop-Dimmer-White-R12-TBL03-10W/203812625


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