Dimmer for one lamp


If you want to create a more pleasant atmosphere in your living room and you don't have the budget to control it, this is the solution. voltage regulator circuit based on a triac. For very little money, and even using recycled materials, you can build your own dimmer switch. This way you can raise or lower the light in a room according to your needs at any given moment. You can use it for a table lamp as well as for one of your ceiling lights, as long as it is for normal or energy saving bulbs (not for LEDs or fluorescent bulbs).


  • Two-core copper cable with a plug to connect it to the mains or 2.5mm two-colour copper cable (if it is going to be flush-mounted). For the cable you can use the cable of an appliance that does not work (hairdryer, table lamp, television, washing machine, toaster,...), so that saves you a lot of money. It will be connected to the input (E) shown in the diagram.
  • Fine copper wire which you can obtain by stripping any old cable or buying it from an electronics shop. A thickness of 2mm is sufficient.
  • Glass fuse of 5A, represented by F in the diagram. If you want, you can also buy a fuse holder, although it is not strictly necessary because the fuse can be soldered directly to the terminals.
  • Isolating box or without it for flush mounting. The one I have made is external and I have placed it in a machined box, but you can build a box with wood or plastic. Another option is to embed it in the wall, inside a junction box, so that it is not visible.
  • Printed circuit board to etch it with the right circuit (this option is more expensive and complex, as you have to use etching acids and the right material). But there is an easy and cheap alternative, mounting it on a plate or hard plastic.
  • Heat sink for triac. With a screw/nut of the appropriate size to hold the triac.
  • Triac BT137.
  • Diac BR100.
  • 2 polyester capacitors of 39nF/250vin the circuit represented as C1 and C4.
  • 2 polyester capacitors of 22nF/250vrepresented by C2 and C3.
  • Linear potentiometer of 470KΩ with switch. In the drawing it is P1. This element will serve as a voltage regulator.
  • Resistance of 12KΩ 0,5w. This resistor is the R1.
  • Resistance of 100Ω 0.5w, for R2.
  • Shock coil with ferrite (L).
  • 2 plug-in connectors double to make the output (S) and input (E) connections.


  • Soldering iron and tin.
  • Saw or saw.
  • Drill and very fine drill bit.
  • Screwdriver.
  • Crimper (wire stripper).

If you follow the money-saving tips I've given you, it can work out for less than €10.

To assemble everything properly, the electrical circuit diagram you need to form is as follows:

Dimmer circuit

The procedure to assemble it is simple, in a few steps you will have it ready. Proceed as follows:

  1. To make it easier, you can start by cutting out a piece of sheet metal or drywall or hard plastic (if you prefer, you can engrave a custom printed circuit board) and draw the circuit schematic on it. The dimensions can be 10x3cm or larger if you want to work with more space.
  2. Now go to element by element. Place each element in the place where the corresponding symbol is in the drawing you have just made. You can mark where the pins fall in order to drill the board and make the connections on the other side. The rest can be placed indistinctly, without taking into account the polarity (one pin is the same as the other...). But don't do that with the potentiometer and the triac.
  3. Potentiometer and triac need to be fitted in a special way. Only terminals 1 and 2 of the potentiometer will be useful, 3 will be left free (note that they are numbered in the diagram above). Look at the following image and place the potentiometer (left) and the triac (right) as shown, to identify the pins: triac and potentiometer
  4. You already know the location of each component and how to connect them. You can drilling the holes to insert the pins of each component (don't forget to mount the triac on the heatsink and screw it to the heatsink). Proceed to assemble them using copper wire and soldering on each pin with the soldering iron and solder. You can look at the following diagram:Schematic drawing
  5. The tokens can go screwed or glued to the board. In the circuit diagram you will see that the mains connection cable is connected to the input (E), which is one of the connection plugs. The other plug is for the output to the lamp or bulb.

I hope you liked it and find it useful. Please comment if you have any questions or problems. The final result of the dimmer switch you can see it in the following video:


Read more - How to build your own high-powered homemade LED torch

16 thoughts on “Regulador de intensidad luminosa para una lámpara”

  1. That jumper didn't work for me, I don't understand it. Without the potentiometer it stays on just the same

    1. Hello John,

      Thank you for your interest. As for the circuit, I don't know exactly what you have done, but the potentiometer serves the function of a dimmer. With it, you can adjust the intensity of the bulb...

      Best regards and thank you for your comment.

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