Attempting to make capacitor....Unsuccessfully!

[verticalhover]

Hey, new to the forum. I've been trying several different designs for a homemade capacitor. I'm interested in antique electronics such as old radio's etc. So I like to make as many of the components as I can. But I'm having a baffling problem with my capacitors.

Just as a test, I started out using a plastic film canister wrapped in aluminum foil for the positive terminal. I inserted a steel nail in the lid to act as my negative terminal. I filled the canister with plain salt water. I've attempted to charge it using between 9 and 12 volts DC without success.

My second attempt was to use a flat section of plastic with foil on both sides. This also failed.

This is one of the few components that I've failed to make over the years. I must be missing something. I've even gone back and studied other designs and watched others build them exactly the same way. But I'm at a loss as to what is missing from my designs.

Any ideas?

 

[ericgibbs]

Hey, new to the forum. I've been trying several different designs for a homemade capacitor. I'm interested in antique electronics such as old radio's etc. So I like to make as many of the components as I can. But I'm having a baffling problem with my capacitors.

Just as a test, I started out using a plastic film canister wrapped in aluminum foil for the positive terminal. I inserted a steel nail in the lid to act as my negative terminal. I filled the canister with plain salt water. I've attempted to charge it using between 9 and 12 volts DC without success.

My second attempt was to use a flat section of plastic with foil on both sides. This also failed.

This is one of the few components that I've failed to make over the years. I must be missing something. I've even gone back and studied other designs and watched others build them exactly the same way. But I'm at a loss as to what is missing from my designs.

Any ideas?

hi,
What value of caps are you trying make.?

 

[verticalhover]

I haven't set a specific value yet. Just trying to make it work right now. I plan on using it mainly for RF circuits, ocillators, etc.

 

[transistor495]

What you've made are capacitors only. They can hold very little charge in pf's more likely..how you're testing whether they're charged or not?

Heard about stray capacitance? If you use the 'capacitors' what you've made in VHF circuits they may perform nicely

 

[ericgibbs]

hi,
What value of caps are you trying make.?

Look thru these links, enjoy.
homemade capacitors - Google Search

 

[verticalhover]

I've been using both digital and analog multimeters. I haven't been able to detect even a slight charge in the caps I've made. I've varied charging times from between a few seconds, all the way up to a minute. I've tested my equipment on standard caps and it all checks out fine.

 

[Boncuk]

Hi,

you must have been missing a lot at school.

Salt water solution is conductive!.

A capacitor should be made of two plates (aluminum, copper or iron, depending on your budget) being isolated by a non-conductive dielectricum.

Here is a simple experiment you can use to make a capacitor:

Use either of the above mentioned foils and use silicone oil as dielectricum. (also used to power tesla coils)

The size of the plates, their distance and the dielectricum is decisive for the capacitance.

To make a capacitor of 1F you need two plates with an area of about 10 square meters at a distance as high as the "Cologne Dome" (75m high cathedral), using air as dielectricum.

Good luck

Boncuk

 

[shortbus=]

Some plastics are also "semi-conductive", the black and gray colors more so than others. The salt water also is a bad idea because if it is spilled/splashed when filling the canister it will conduct to your outer foil plate.

For a 'Whimsherst Machine' I made I used foil on the out side and BB gun BB's for the inner plate. A glass jar was the container, works perfect.

 

[Nigel Goodwin]

The point here is that the capacitors he's attempting to make are of such small capacitance that you can't charge them up and measure the charge.

The jam jar capacitor mentioned is also a very low capacitance, and only works because you're charging it to stupidly high voltages

 

[Dr_Doggy]

if you are up to making radio capacitors all you need is foil, it should be spread over "2 opposite sides" of the dielectric material, which is your 2nd ingredient, which can be any non conductive material, thats it

... I bet your capacitors did work, but with such small things charged to only 12v, you wont get much energy out

however if you get your hands on a capacitance meter your device will prolly read a few pico-farads at least

and they would probabally work in a crystal radio kit tuned with a proper coil

 

[verticalhover]

if you are up to making radio capacitors all you need is foil, it should be spread over "2 opposite sides" of the dielectric material, which is your 2nd ingredient, which can be any non conductive material, thats it

... I bet your capacitors did work, but with such small things charged to only 12v, you wont get much energy out

however if you get your hands on a capacitance meter your device will prolly read a few pico-farads at least

and they would probabally work in a crystal radio kit tuned with a proper coil

Thanks! I'm gonna go ahead and try using it, and see if it works in a circuit.

 

[Dr_Doggy]

k, don forget though, the surface area of the foil changes you capacitance, so you will still need the value of the caps so you can calculate your inductor size,

here is a good simple guide that i think should answer all your questions

Chapter 4: Radio

 

[BrownOut]

Hi,

you must have been missing a lot at school.

Salt water solution is conductive!.

It's supposed to be. It's one of the terminals.

 

[shortbus=]

<snip>
The jam jar capacitor mentioned is also a very low capacitance, and only works because you're charging it to stupidly high voltages

It will jump a spark over a 4'' gap before over powering the segments on the disk's

 

[Nigel Goodwin]

It will jump a spark over a 4'' gap before over powering the segments on the disk's

Just pour those electrons in the jar!

 

[transistor495]

I'm interested in antique electronics such as old radio's etc.

Any ideas?

Perhaps this link may give you a clear idea about them. I use them for my VHF FM circuits. **broken link removed** Ultra simple. Both twisted and wound small value capacitors I've seen in old radio electronics. Tuning caps(few hundred pf) are so easy to make using aluminum foil and cardboard Homebrewed Variable Capacitor.

Hope it helps.

 

[verticalhover]

Thanks for all the help and links. I was able to make one that worked today. I used sheets of aluminum foil and wax paper. After attaching the wires, I rolled it up like a burrito. I can't measure the capacitance, but my multimeter measures about 350 millivolts when discharging, so thats definitely a result.