Rolling your own electronics components can be fun, but can also help in explaining how certain items actually work. [Addie] from The Toymakers recently set off to figure out how capacitors work, by making her own.

She understood the general concept behind capacitors and how they are constructed, but she wanted to see how it was done first-hand. To construct her capacitor, she selected aluminum foil as her conductor, and saran wrap as the dielectric. She admits that her first attempt was a failure, but undaunted, she carried on. Friends suggested that her conductors were a bit too small to hold any reasonable charge, so she tried larger sheets of aluminum foil to no avail.

She kept at it and found success after using several feet of foil to construct her capacitor. She charged it with a handful of AA batteries and was excited to see her multimeter come to life when she touched the leads to the cap.

While you likely wouldn’t use a hand-made capacitor in your next build, it is a fun experiment to do with children interested in learning about electronics.

[via Adafruit blog]

In keeping with our opinion that radio operators were the original electronic hackers here’s a guide to building your own transmitting air variable capacitors. Using some roof flashing, Plexiglas, and various fasteners [David Hammack] was able to make it work. It’s not a perfect solution but he has some ideas to make the next one better. Give this a try after you’re done tweaking your crystals and building input devices.

[Thanks Rich]

Most ICs need to be decoupled from their power supply, usually with a 0.1uF capacitor between each power pin and ground. Decoupling is usually used to remove noise and to smooth power fluctuations. Every project will need a few decoupling capacitors; our mini web server project has three ICs that require a total of 11. This can be an expensive part to buy in singles, so it’s crucial to stock up online. Read more about our favorite bulk through-hole and surface mount decoupling capacitors after the break.

The capacitors we selected should be sufficient for most projects. All three parts are rated for 50volts, far more than most digital circuits. We used cheap 20% tolerance parts because it’s not critical that decoupling capacitors be exactly 0.1uF. Higher or lower tolerance capacitors will also work, but there’s no advantage to using high quality decoupling capacitors. Here’s a breakdown of the 0.1uF capacitors pictured above:

C1 through-hole 0.1uF capacitor, such as Mouser #594-K104M15X7RF53L2, ($4 per 100 ) – This cheap 0.1uF capacitor will fit almost any design that calls for through-hole decoupling capacitors. Leads are spaced 2.5mm apart, and fit footprints such as C-EU025-025×050 in the default Cadsoft Eagle rcl library. Part number -L2 has straight legs, -K2 has an outside kink as shown in the picture.

C2 1206 SMD 0.1uF capacitor, such as Mouser #77-VJ12Y50V104K, ($4 per 100) – You might be tempted to try 1206 size parts in your first surface mount experiments. We urge you to skip 1206 and head right on down to 0805. 1206 parts have very little cost benefit over through-hole parts because they’re no longer an industrial favorite. 0805 is just a bit smaller, but costs half as much. Fits Eagle footprint C-EUC1206 in the default rcl library.

C3 0805 SMD 0.1uF capacitor, such as Mouser #80-C0805C104M5R, ($2 per 100) – An 0805 capacitor fits between two pins on a through-hole DIP chip, and aligns nicely with pins on an surface mount SOIC chip. All our new designs, surface mount and through-hole, incorporate this dirt-cheap decoupling capacitor. Fits footprint C-EUC0805 in the default Eagle rcl library.

Check out our previous parts posts on the LM317 adjustable regulator and tactile switches. Are there any parts you’d like us to cover?

The Leyden jar capacitor posted the other day fails to compare to what [FastMHz], one of the members over at the 4HV.org forums, has been busy building, a 24kj capacitor discharge bank. This capacitor bank will be configured for 4500v @ 2400uF and can be charged up slowly using microwave oven transformers. It can then release all its stored energy in under a millisecond through a triggered spark gap. This allows for some pretty big sparks as seen in this video, we are not sure about the laughing in the video maybe the power has gone to his head?

A bank like this can be used for a railgun, induction launcher, or exploding things in general. Coin shrinking and can crushing require much quicker discharge rates than what electrolytic capacitors are really capable of, and generally perform better with large pulse capacitors, however it will be interesting to see the final use for this potential energy.

The first step of the process is finding electronics you don’t mind taking apart. Next place the PCB you’ll be stripping in a vice, with the components facing away from you and the solder side facing towards you. Grip the component you want with a pair of pliers, and apply a hot soldering iron to the solder that is holding the component. The solder will melt and allow you to safely and cleanly remove the component.

This process can be applied to virtually any component on an PCB, and the author of the guide, [Patented], got a lot of components this way, including resistors, capacitors, switches, audio jacks, and much more. Don’t forget to toss any free-floating metal or plastic parts in the recycle bin when you’re done. You can feel good about the fact that nothing was wasted, you found parts for your next project, and you cleared out some space.