# Will My DIY Capacitor Light Up a 6VAC Bulb in Series?

• B
• avicenna
avicenna
TL;DR Summary
aluminum foil capacitor with paper dielectric
Say I build a parallel capacitor from two 10cm x 10cm aluminum foil with one sheet of writing paper in between as dielectric. I press the foils together with a weight and a flat piece of plastic/glass.

I can power on a 6VAC incandescent bulb with a 6VAC power supply. Now if I connect my capacitor in series with the bulb, will the bulb light up.

avicenna said:
Now if I connect my capacitor in series with the bulb, will the bulb light up.
The capacitance will be about 200 pF.
Reactance, Xc, will be about 16 MΩ at 50 Hz.
Current will be less than 6 V / 16 MΩ = 0.4 uA
That current will be insufficient to light a filament lamp.

berkeman
Baluncore said:
The capacitance will be about 200 pF.
Reactance, Xc, will be about 16 MΩ at 50 Hz.
Current will be less than 6 V / 16 MΩ = 0.4 uA
That current will be insufficient to light a filament lamp.
Thanks.

avicenna said:
Thanks.
Baluncore said:
The capacitance will be about 200 pF.
Reactance, Xc, will be about 16 MΩ at 50 Hz.
Current will be less than 6 V / 16 MΩ = 0.4 uA
That current will be insufficient to light a filament lamp.
My estimate:
capacitance = 200 - 400 pF.
reactance(1/(2πfC)) = 16 MΩ

This site, All About Circuits has an online calculator:

Gives impedance to be 1591 Ω ; I think wrong.

Is there a simple way to build a home 100 - 1000 μF capacitor?
Best as a parallel plate capacitor with small area plates.

avicenna said:
Gives impedance to be 1591 Ω ; I think wrong.
I think you left out a few powers of ten or did not specify the frequency.

avicenna said:
Is there a simple way to build a home 100 - 1000 μF capacitor?
Best as a parallel plate capacitor with small area plates.
I do not think so.
You would need too many layers, with molecular thickness insulation and an electrolyte with a high dielectric constant.

Baluncore said:
I think you left out a few powers of ten or did not specify the frequency.
Baluncore said:
I think you left out a few powers of ten or did not specify the frequency.

I do not think so.
You would need too many layers, with molecular thickness insulation and an electrolyte with a high dielectric constant.

I do not think so.
You would need too many layers, with molecular thickness insulation and an electrolyte with a high dielectric constant.
Yes, I think no way for super capacitor this easy.

About the site, I think really bad. My entry was 200pF, 50Hz only

avicenna said:
About the site, I think really bad. My entry was 200pF, 50Hz only
It works correctly for me, 200 pF at 50 Hz = 15 915 494.3092
I note that 2 uF at 50 Hz gives 1591.5494
Did you click on the calculate button?

Baluncore said:
It works correctly for me, 200 pF at 50 Hz = 15 915 494.3092
I note that 2 uF at 50 Hz gives 1591.5494
Did you click on the calculate button?
OK. The display box in my linux system is only 4 digits wide; I have to use the right arrow key to get the rest of the digits!

I reduce the font size and got the full value!

Maybe start with a bead of tantalum or titanium powder, electrically bonded and sintered on a wire lead. Next, oxidise the entire surface of the bead, inside and out. You then have an oxide insulator with a high dielectric constant. Plate the outside of the oxide with a metal and attach a second lead.
https://en.wikipedia.org/wiki/Tantalum_capacitor

Look at the materials at the bottom of this list.
https://en.wikipedia.org/wiki/Relative_permittivity

Alternatively;
Get two rolls of aluminium foil, and two rolls of cling-film, from the supermarket. Roll the four layer sandwich tight onto a cylinder. Make connections to the two foil layers.

To solder aluminium, wet the area with cooking oil, scrape the Al oxide surface through the oil, to make it shiny, bare Al, then solder coat the Al surface through the oil. Solder the leads onto the plated patches. Practice that technique with scraps of foil, before rolling the capacitor.

Baluncore said:
Maybe start with a bead of tantalum or titanium powder, electrically bonded and sintered on a wire lead. Next, oxidise the entire surface of the bead, inside and out. You then have an oxide insulator with a high dielectric constant. Plate the outside of the oxide with a metal and attach a second lead.
https://en.wikipedia.org/wiki/Tantalum_capacitor

Look at the materials at the bottom of this list.
https://en.wikipedia.org/wiki/Relative_permittivity

Alternatively;
Get two rolls of aluminium foil, and two rolls of cling-film, from the supermarket. Roll the four layer sandwich tight onto a cylinder. Make connections to the two foil layers.

To solder aluminium, wet the area with cooking oil, scrape the Al oxide surface through the oil, to make it shiny, bare Al, then solder coat the Al surface through the oil. Solder the leads onto the plated patches. Practice that technique with scraps of foil, before rolling the capacitor.
Thanks. But I am not at the level to try this yet.

avicenna said:
Thanks. But I am not at the level to try this yet.
You might try to make the alternative foil and film capacitor using kitchen commodities from the supermarket. Stagger the two foils so they hang out at opposite ends of the roll, then use clips to contact the foil.

Baluncore said:
You might try to make the alternative foil and film capacitor using kitchen commodities from the supermarket. Stagger the two foils so they hang out at opposite ends of the roll, then use clips to contact the foil.
I realize my idea about my capacitor experiment wrong. So I don't need my capacitor for now.

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