charging a capacitor and discharging it slowly

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sstambach

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Hey guys,

I'm trying to create a simple circuit in which I can use a solar cell to charge a large capacitor, which then can get discharged through a resistor to light a single light bulb for a fairly long time. Does anyone have a simple schematic for such a circuit?
 
Try a small Sealed-Lead-Acid battery. A capacitor's voltage drops exponentially with time, while a battery will hold up its output voltage much flatter.
 
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Get the flash charging unit from a throw away camera. Replace the charge capacitor with a very large capacitor. I replaced one with a 45,000. uf cap it takes about all day for it to charge up. Replace the 1.5 volt DC battery with solar cells. Connect a neon light bulb in parallel with the capacitor with a resistor in series with the neon light. You probably don't want it to light up during the day so put a switch in series with the neon light too. When it gets dark the neon will light up after you close the switch. The size of neon determines how long it stays light up. 15 watt neon will last about a hour or so. LEDs might work better than neon I have not tried that.

I rigged a few of these as booby traps for thieves. Thieves broke into the house once, broke into the garage once, tried to steal the vehicle in the driveway. Put a large capacitor on a tree limb about 10 ft up with the flash unit to charge it. 2 tiny bare wires hanging for the tree in the dark connected across the capacitor. Someone walks into the naked wires in the dark the capacitor discharges on their face or arm. I also have them in other places, door knob works great it would knock you silly. Get in the vehicle after dark set on the seat or touch the stearing wheel and see what happens. Thieves are stupid you put a tiny flashing neon out in the yard on in a dark room thieves can not resist walking over to see what it is, BOOM the capacitor will knock them silly.
 
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Then the Police come and arrest you, what you're doing is criminal and a fairly serious offence.
 
Getting robbed is a very personal feeling.

The feeling of being violated, and wronged can lead to such precautions being taken.

There was a recent television show that showed a home that was repeatedly burgled. The owner, fed up, wired a zap circuit to the window frame, then the gate.

The robber entered the yard through the gate, triggering the system.

He went to the same window he always used to break in, and ZAP!

He was thrown to the ground.

After he got up, he TRIED TO GET IN AGAIN!

ZAP. Thrown down again.

Then he finally decided to leave.

ZAP.

Got hit by the booby-trapped gate.

The homeowner had set up a video camera to be activated when the gate was opened the first time.

The host of the TV show had no problem airing this, and the home-owner was only warned by the local police.

Self defense and property defense laws doesn't allow for "automated" killing machines. At least not in my jurisdiction.

Put a sign on the window that says: "Turn around. Im going to f'in shoot you."

If they can read, it usually leads to them leaving WITHOUT turning around.
 
Electronics Goldmine has 2600F UltraCapacitors for sale.

You can charge these up and slowly discharge them for months.

You need not go that far. Supercapacitors are used for brown-out backup, and short-term power supplies in many consumer electronic devices.

A battery is much easier to use, but the supercaps are much smaller.
 
That sure beats the .47F caps that I know about! 2600F will run a LED for...lets see...52 times as long as half a F? Always with the advances in what's available!

Hang on...10 for $150 and they are rated at 2.5 volts. Seems like a pretty slim voltage margin to run an LED with. Of course, if you accept the deal, you'll have 10 of them and you can store lots of voltage, but I'd buy a flashlight. I'm too cheap to spend $150 for 2.5 volt caps and too lazy to carry 2.6 pounds of capacitor just to get to 5 volts.
 
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With the 2.5v 2600F cap and a Joule thief, the LED might run FOREVER!

not really. But a LONG time.
 
Nigel Goodwin said:
Then the Police come and arrest you, what you're doing is criminal and a fairly serious offence.
Click to expand...

Thieves are criminals. I have a right to defend my property. Tennessee State Law changed last summer. I can legally kill the theives if they are on my property.
 
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gary350 said:
Thieves are criminals. I have a right to defend my property. Tennessee State Law changed last summer. I can legally kill the theives if they are on my property.
Click to expand...

Jam-a-lamb! Im moving to Tennessee!

Can you kill them by proxy?

Like using landmines? Or do you HAVE to be present and witness the theft? (Or attempted theft)
 
You can not build a booby trap that will kill a thief. Booby traps that hurt thieves are legal. If they are on my property I can legally shoot them thats the law.
 
I was thinking (agreeably) that some kind of joule thief circuit would do well with a 2600F cap. A joule thief would work well at that voltage, but it has 2 problems besides the price of the capacitor: Even one of those caps is bigger than a (2) D cell flashlight and any mention of a thief on this thread might get somebody shot!

I'm gonna stick with my (3) AAA cell LED flashlight. It's surprisingly bright, running 21 LEDs, and it fits in my pocket without looking like I'm happy to see you.
 
How much light do you need?
A simple solar garden light are dirt cheap and comes with solar panel, 1 AA nicad battery, and a ultra bright led, also a daylight sensor built in to prevent it discharging through the day.

All for less than the cost of a large cap.
 
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