Light dimmer circuit

This simple circuit is made in order to regulate the luminous intensity of one or several incandescent lamps, or, as we know them, light bulbs, with a potentiometer.

More details

Data sheet

DesignSchema and circuit
ViewNo display
Supply voltage220 Volts
ElectronicAnalog electronics

More info

The maximum intensity which can withstand this design is around 500 watts.

There isn’t a lot to comment about the scheme: it is based on the TRIAC (triode for alternating current), which has a potency BT136, and it controls the luminous intensity depending on bigger or smaller resistance applied to “Gate” .

The 500K lineal potentiometer is in charge of this regulation. The R2 resistor serves to regulate the minimal light threshold.

We have included a 100 uH coil and a 100K condenser to free the circuit from the possible interferences which might be caused in the electric current while it is functioning.

The electrical connector for three connections is meant to connect:
-In the connection (X2-3) one electric current pole and one light bulb terminal.
-In the (X2-2) another light bulb terminal.
-And, in the (X2-1) another electric current pole.

The potentiometer had to be placed in the centre because of esthetical reasons.

Since the box wasn’t placed high enough, we had to make a hole in the panel to build in the potentiometer (see the photos below), so we included two “pinheads” (JP1 and JP2), to which we connected the switch’s terminals that were incorporated in the potentiometer.

The wiring diagram.

Esuqema regulador de luz

The circuit board.

We have placed the coil and TRIAC in the lower part of the panel since the height of the box was preventing us to put it in the vertical position.
By the way, the box is a “Supertronic, reference PP6N”.

Circuito impreso regulador de luz

Our light dimmer.

The panel of the circuit bears a rectangular hole for the potentiometer in its centre.

Placa con agujero para el potenciómetro

Details of the connection switch potentiometer in the wiring scheme marked as "Pinhead" JP1 and JP2

Detalle regulador de luz

The components welded together on the panel.

Componenetes soldados del regulador de luz

Finished light regulator.

Regulador de luz

NOTE: If this scheme is going to be used with 110V voltage, a 270K resistor parallel to the potentiometer pines should be introduced.

The scheme and the circuit board should be in the same folder and they should have the same name, you should only change the extension to .sch for the scheme and to .brd for the circuit board, this way both of them will be recognized and associated by Eagle.

The file to download is compressed, to extract it, you should enter a password:

If you don´t know how to make a printed circuit boards click here.