Homebrew High Voltage Capacitors on the Cheap




Have you ever wanted to build a high voltage project, yet were discouraged by the high prices of high voltage capacitors? Have you ever wanted the parts to build a Tesla coil cheaply? If so, then this instructable is for you. in this instructable, I will show you how to build high voltage capacitors out of common household objects. The video below will compliment this instructable.

Lets get started!

Step 1: Tools and Materials

For this project, you will only need a few household materials:


  • Sharp knife
  • Scissors
  • Multi-meter


  • Aluminum Foil
  • Polypropylene Page Protectors
  • Multi Stranded Wire
  • Scotch Tape

Step 2: Preparing the Page Protectors

To prepare the page protectors, you will need to cut them so they will be able to fold open like a book. You can do this by using scissors to cut off the top of the page protector, and the white part with binder holes. After this, you should have a piece of clear plastic that can be folded open easily. You will need two page protectors for each capacitor.

Step 3: Cutting and Sizing the Foil

The next step is to cut the aluminium foil to size. to do this, you will first need to pull about 3 feet of it out of the box. Then, measure out a rectangle of foil that is roughly 1.5cm smaller than the page protector on all sides. After that, use a sharp knife to score the aluminium foil along the edges of the measured rectangle. Finally, gently pull on the foil to separate the foil on the scores that were made. You should have a piece of perfectly cut foil that is slightly smaller than the page protectors. You will need two foil rectangles for each capacitor.

Step 4: Inserting the Foil Into the Page Protectors

After the page protectors and foil are prepared, slide the foil rectangles into the prepared page protectors. Slide them all the way down to the bottom crease in the page protectors. You should now have a completely insulated piece of aluminum foil.

Step 5: Adding the Wiring

To add the wiring, you will need to take two wires, and strip and flay the edges. You will need to then set the two page protector-foil stacks on top of each other. Then, take the flayed wire, and tape it to the aluminium foil inside the page protector. Do this with both pieces of foil.

Step 6: Rolling the Capacitors

The final step is to roll the capacitors.

To do this, start at the end where the page protector is folded over, and start tightly rolling the capacitor. It should be about 3/4 inch in diameter when completely rolled. Then, tape the capacitor so that it will not unroll. After this, your capacitors should be ready to test!

Step 7: It Works!

The capacitors should work now! To test them, hook it up to a multi-meter with a capacitance function. It should read the capacitance. My capacitors had a capacitance of about 4-6nF each. The capacitance depends on how tightly you roll them. You can also test them by hooking them up to a high voltage source and seeing if they discharge a spark when the power source is turned off. Good luck this project and any other projects using high voltage capacitors!

Thanks for reading!



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    5 Discussions


    2 years ago

    Your capacitance would go up higher if you removed one sheet of the plastic. In other words use only one plastic sheet protector and two aluminum foils. Put one aluminum foil on the outside of the plastic sheet protector and the other one inside the plastic sheet protector and then roll them up and measure. You presently have two plastic sheets next to each other in your present design and that makes the capacitance lower. The thinner the insulating material between the two foils, the higher the capacitance. JMHO

    2 replies

    Reply 2 years ago

    you are correct that there will be a higher capacitance, but you'd sacrifice some of the insulation between plates, reducing the voltage the insulators can withstand. by making a matrix of series / parallel capacitors, you can increase both voltage and capacitance


    Reply 2 years ago

    I saw others with the plastic film for food preservation ... It is very thin but isolates it.

    Abe Sam

    2 years ago

    You did a good job in explaining your methods. Impressive!


    2 years ago

    I'm just wondering how high a voltage will this take as you have made it and what higher voltage might be obtainable using double or tripple layers of plastic insulation or indeed other insulations like say black visqueen?