How to make a homemade variable capacitor

In almost all projects involving electronics or electricity, capacitors are indispensable, and in some cases, capacitors are necessary. variable capacitors that fit the characteristics of our project, as in the case of crystal radio receivers that require a variable capacitor. Next, we will see how to make a homemade variable capacitor with materials as common as razor blades.

Variable capacitor of commercial type


To build our homemade variable capacitor, we will need:

- Two pieces of plastic or wood 55 mm x 60 mm.

- Six screws.

- Nuts and washers.

- Two razor-blade sized metallic conductive foils.

- Adjustment knob (control knob) for varying the capacitor power (one of those nut-type knobs that fit on a screw).

- 8 razor blades (razor blades).

- A small wooden or plastic stop just a little higher than a razor blade and about 45mm.

Variable capacitor construction

To begin the assembly of our condenser, we take the two pieces of wood or plastic and with the help of a drill, we drill four holes 5mm away from the edges of the piece in the four corners, and two holes in the upper part with a distance of about 40mm from each other.

Then, we take one of the pieces, this will be our base and with the help of glue we place our wooden or plastic top.

Sketch of the assembly of the homemade variable capacitor

Next, we place the screws in the corresponding holes, put washers on the screws that are located in the corners and tighten them to the wood with nuts. The screw of the fixed sheet, we also secure it with a nut to the wood and we pass it through the first conductor, while the screw that we will use as a mobile part, we will not adjust it completely to the wood, we will only place the nut so that it does not come out and allows us to turn the screw at will. Over the nut, we will place the second conductor.

Now, we place the first razor blade on the fixed part of the assembly, then place two washers on the nut of the movable part and place the second razor blade on top of it, facing the first razor blade. Next, we place four washers on the blade of the fixed part and place the new blade. From now on, we are going to place the same number of washers on each screw as we place the new blade. razor blades.

Homemade variable capacitor razor blade arrangement

When we get to the last razor blade on the fixed part, place a washer and tighten it with a nut until it fits with the plastic or wooden stop and it is as one piece. Then, we place four washers on the mobile part (on the razor blade), a pressure washer and a nut until it fits, taking care that the nut on the lower part does not tighten and lose its ability to move.

Then, we place a nut on each screw, all at the same height and on these nuts we place the other piece of plastic or wood, closing the assembly. On the outside of the cover that we have just placed, we adjust the screws of the corners and the fixed part to the cover and on the screw of the mobile part, we place the control button so that we can adjust the capacity of our homemade variable capacitor.

Drawing of the homemade variable capacitor to be constructed

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