Charging a Capacitor and Shocking

[zking786]

I've been experimenting with capacitors (50-100uF from camera circuits). I'm wondering how I can charge a capacitor. I can't just plug it into a source of EMF, I probably need to design or find some sort of circuit, right?

 

What's the best way to charge metallic objects? I don't have a Van de Graaf machine and can't produce enough charge by induction by rubbing two materials. Can I use a capacitor to charge metallic objects?

[5614]

If you connect a capacitor to a battery it will charge.

 

Do it and then connect the capacitor to an LED and the LED will light up briefly until the cap has been drained, which with a 100µF cap will happen quite quickly. As LEDs, caps and batteries are all pole sensitive make sure you have the positives and negatives connected the right way around. Also do not touch both legs of the cap because then it will drain through you, although it is such a small current you will not notice the effect, but the cap will then be empty.

 

You could use capactiors to charge electric plates, yes.

[zking786]

How can I use a capacitor to charge a plate?

 

When I plugged the capacitor to a source of EMF, 1.5V battery and later a 19.5V battery eliminator, it only charged to about 3V. When I removed it from a camera, though, I got a HUGE shock -- more than 3V. Any idea why it won't charge fully? Is this because of the poles?

 

Why are capacitors pole sensitive? Aren't they essentially two parallel plates separated by a dielectric?

 

Thanks for the help!

[YT2095]

you have to charge it through a Diode, current will go in, but wont come out, then Discharge it directly from the cap.

[5614]

Why are capacitors pole sensitive? Aren't they essentially two parallel plates separated by a dielectric?

Not all caps are pole sensitive, but electrolytic capacitors are, see here:

http://en.wikipedia.org/wiki/Electrolytic_capacitor

[YT2095]

there ARE electrolytic caps that are Not polarised though, usualy the Radial lead ones and often used in passive crossovers in Audio equipment.

 

the sort in Cam flashes are Always polarised though, it`s odd that you say 50V though? cam flash types are normaly the 400v mark.

[5614]

He said 50-100µF... not volts. As you said caps for camera flashes are normally about 300V to 400V, although those caps are also normally a higher capacitance (150µF - 200µF).

[YT2095]

caps are rated Voltage and Capacitance (50-100uf) reads 50v 100uf.

(sometimes temp and VAC ratings too).

 

so what IS "(50-100uf)" suposed to mean?

[zking786]

When I say 50-100uF, I mean different capacitors of varying capacitances.

 

Also, I've been told that I need to use an inductor and a transistor to charge the capacitor. (http://www.ee.washington.edu/conselec/CE/kuhn/labs/camera/fl.htm). How would directly charging the capacitor using a AA battery yield a high enough voltage? Doesn't it need to be steped up using an inductor?

 

Also, why am I able to charge a capacitor to 1.5V or -1.5V when I plug it directly into the 1.5V AA battery? If it's pole sensative, shouldn't it only work in one direction?

 

How would I be able to charge a plate conductor?

 

BTW, thanks for all the answers.

[YT2095]

Numners Mine:

1) When I say 50-100uF' date=' I mean different capacitors of varying capacitances.

 

2) Also, I've been told that I need to use an inductor and a transistor to charge the capacitor. (http://www.ee.washington.edu/conselec/CE/kuhn/labs/camera/fl.htm). How would directly charging the capacitor using a AA battery yield a high enough voltage? Doesn't it need to be steped up using an inductor?

 

3) Also, why am I able to charge a capacitor to 1.5V or -1.5V when I plug it directly into the 1.5V AA battery? If it's pole sensative, shouldn't it only work in one direction?

 

4) How would I be able to charge a plate conductor?

 

BTW, thanks for all the answers.

 

1) Ok thnx for that clarification

2) that`s the usual way it`s done, yes. the "Inductor" is indeed a Step-Up transformer, and takes the 1.5v and quite alot of current from the AA bat, and depending on the ratio, steps the voltage up accordingly to more than 1.5v but a proportionaly lesser current.

3) pole sensitivity at those types of voltages are negligable, try it at the Voltage rating of the cap that isn`t AC rated and it`ll blow!

4) I don`t understand the question?

[zking786]

Thanks for all the answers YT2095!

 

With regards #4, I'm trying to use the charge stored in the capacitor to charge a metallic object (like a rod or a plate). I doubt simply hooking one end of the capacitor to the object will charge it. How would you recommend charging it? In post#2, 5614 says it's possible.

 

Also, why use a diode? The capacitor can't charge a standard AA battery, can it?

[YT2095]

ok, for a start No you cannot "Charge" an object alone, the charge Must be in relation to something else, and so you could charge a door handle relative to the Ground or any 2 objects that conduct really, but you cannot just make something Positive or Negative like you`re thinking, it`ll not work, the/A circuit must be made for electrons to flow.

 

that capacitor can indeed charge the AA bat again with near the same amount as it took out of it, sure

[zking786]

I know what you mean, charge must be relative to something. I'm refering to the ground as a reference point, or a human body . If I connect one end of the capacitor to a metallic object, the charge should flow from the plate within the capacitor to the object, right? So, theoretically, if I touch one end of the capacitor, will I get shocked?

 

Will the method I described work to charge a metallic object/conductor? If not, what will?

[YT2095]

well if you charge the cap to 300vdc stick one end on you and the other end of the cap to a tin can or metal bar, I for one would NOT want to touch it!

[Externet]

Hi.

...."I've been experimenting with capacitors (50-100uF from camera circuits). I'm wondering how I can charge a capacitor. I can't just plug it into a source of EMF, I probably need to design or find some sort of circuit, right?

 

---->Right, and the best circuit is the one it was connected to within the camera. Use the whole thing and not only the capacitor.

 

...."What's the best way to charge metallic objects? I don't have a Van de Graaf machine and can't produce enough charge by induction by rubbing two materials. Can I use a capacitor to charge metallic objects?"....

 

---->You can charge a metallic object that is isolated by contacting the charged capacitor between the object and ground

 

And yes, the capacitor from a disposable camera flash is rated at least 350 Volts, and around 150 µF.

The 1,5 volt cell charges it to 350 V by means of that small circuit you didn't pay attention to.

If you touch the charged terminals of the capacitor you will get the nasty giggles.

Miguel

[5614]

When you originally mentioned charging plates I thought you mean take the +ve end of the cap and place it on a metal plate and take the -ve end and place it on a different plate.

 

If you did that then the plates would take on the charge of the cap. In this respect you can treat the cap as a battery. Just as you could connect the battery to two plates and there would be a voltage difference across the plates you can do the same with a cap.

[YT2095]

alternatively, for really High voltages, you can use a Spark-Gap to charge a cap with instead of a Diode.

 

Like I`m going to have to with my 60,000 Volt Lexan/Alu capacitor whos plates I`m having specialy cut tomorrow WOOT!

[zking786]

When I hook the capacitor to the battery and connect a diode to prevent backflow, it only charges to 1.4V (approximately the voltage of the battery).

 

Do I have to use an inductor? Or am I doing this incorrectly?

[Jacques]

If I remember well, Electronic flash use capacitor bank.

The capacitor bank use a lot of capacitor on a circuit made to charge the capacitors in parallele and discharge them in serie. For example if you have 100 capacitor and apply 6V to change them in parallele and hook them in serie you will end up with 600V . The electronic circuit is doing all the job of charging in parallele and discharging in serie.

[5614]

Err, the cap used for camera flashes is just a single cap, no banks.

 

YT: What are you going to do with a 60,000V cap? Tesla coil?

[YT2095]

YT: What are you going to do with a 60,000V cap? Tesla coil?

 

charge it up with my new 10 stage Cocroft Walton voltage multiplier

after that, I`ve no idea what I want to do with it yet, it`s just a Building block/starting point, I might try a Can Crusher

[5614]

What's its capacitance?

[YT2095]

I`ve no idea yet, I`ve only just got back from cutting the plates.

there are 5x 1mm Alu plates 63cm X 37cm.

6 Sheets of 7mm Lexan as the dielectrics.

 

and since I can`t stand Maths, I`ll just wait until I`ve built it and stick a capacitance meter on it

 

I`ll need alot of room and some help with moving it when it`s done also, this sucker`s gunna weigh a ton!

[5614]

Have fun and tell us how it goes!

[zking786]

"When I hook the capacitor to the battery and connect a diode to prevent backflow, it only charges to 1.4V (approximately the voltage of the battery).

 

Do I have to use an inductor? Or am I doing this incorrectly?"

 

So, any ideas?