Question about capacitor charging

In summary, someone knocked over a power box, causing the capacitors inside to be charged. A series resistor was then used to discharge the capacitors.
  • #1
baycon
3
0
Other than a power box which can be incredibly expensive, can someone show a good way to charge a capacitor in the 300-450 volt range, and as i am designing a circuit around multiple capacitors would i connect them in series or parallel, and yes they are polarized
 
Engineering news on Phys.org
  • #2
If you cannot answer for yourself, the questions you ask. I doubt the wisdom of your taking on this project.
 
  • #3
I guess that is my fault for not being clear, the rig I was using was broken when someone knocked over the box. What kinds of alternate methods can be used?
 
  • #4
You charge up a capacitor by connecting it across a DC power supply with or without a series resistor.
Given enough time (determined by the capacitance and the resistance of any series resistor) the capacitor will eventually have a voltage across it equal to the power supply voltage.

So, to charge a capacitor, first you need to find a power supply that can supply the voltage required.

Not sure what you mean by a "RIG".

Power supplies don't have to be expensive, but they can sure be dangerous if you are talking about high voltage supplies. So, you might like to read about them on Wikipedia:

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

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

Especially read about the use of bleeder resistors. These are placed across capacitors so that the capacitor discharges into them when the power is removed. Otherwise, some low leakage capacitors can carry a lethal charge for months.

Capacitors can be charged individually and placed in series for discharge. This doubles the voltage available.
Connecting them in series while they are charged would be a risky process unless you did it with a switch inside a box with the capacitors.

Always play it safe with electricity. Anything over 50 volts can potentially kill you.
 
  • #5
Charged capacitors can be very scary! The capacitor in a camera flash unit can give a healthy smack if you touch it by mistake, days after it was used / charged! Be very careful and always discharge capacitors through a resistor, rather than just 'shorting' them out. When you see how hot the resistor can get, you'll realize the actual amount of energy stored.
 
  • #6
Baycon,

Perhaps Integral has got it about right, if you had enough knowledge and experience to tackle this sort of thing safely, you ought to be able to work out a cheap but adequate solution to your power supply problem.

Some time ago, an over-confident student did know enough to get some capacitors charged to a dangerous voltage. He did not know about discharge resistors though, and this nearly cost him his life. The circuit was switched off when he touched it by mistake, but the residual charge was still sufficient to give him a horribly painful shock. Luckily he survived, but sadly he still grew up to become an Electrical Engineer. Don't follow his example!

Regards.
 
  • #7
I guess that student could have been well known to Baycon?
But there are worse fates than becoming an Electrical Engineer.
 
  • #8
A boost converter would probably be the easiest approach, but I must agree with the others in that you must be very careful when working with voltages above 50V. Don't be misled by the size of capacitors your using either, a typical photo flash capacitor for example, is about the size of a "C" battery, yet holds 16.5J of energy when it only takes 16J to kill you. You can also get electrical burns to your inside tissue from current passing thru muscle and skin. A good habit to get into when working on circuits like this is to keep one hand in your pocket to reduce the chance of passing current through your heart, use a voltmeter to verify that everything is discharged before you touch it, and put bleeder resistors on all high voltage capacitors as they can regain some charge even after they have been discharged. Here is a good site about electrical safety
http://ehs.okstate.edu/modules/electric/index.htm
 
Last edited by a moderator:
  • #9
Thanks for all the help guys, I decided to take my own advice and get the help of an electrician that lives across the street. My project worked out after all :)
 

Related to Question about capacitor charging

What is a capacitor?

A capacitor is an electronic component that stores electrical energy in an electric field. It is made of two conductive plates separated by an insulating material called a dielectric.

How does a capacitor charge?

A capacitor charges when an electric current is applied to it. This causes electrons to build up on one plate, creating a negative charge, while the other plate becomes positively charged. The amount of charge stored on the capacitor depends on its capacitance, which is determined by the area of the plates, the distance between them, and the type of dielectric material used.

What is the equation for calculating the charge on a capacitor?

The equation for calculating the charge on a capacitor is Q = CV, where Q is the charge in coulombs, C is the capacitance in farads, and V is the voltage across the capacitor in volts.

What is the time constant for charging a capacitor?

The time constant for charging a capacitor is the amount of time it takes for the capacitor to charge to 63.2% of its maximum charge. It is calculated as T = RC, where R is the resistance in ohms and C is the capacitance in farads.

What is the purpose of a resistor in a capacitor charging circuit?

A resistor is used in a capacitor charging circuit to limit the flow of current and prevent the capacitor from charging too quickly. This helps to protect the capacitor from damage and ensures a more controlled and gradual charging process.

Similar threads

  • Electrical Engineering
Replies
3
Views
2K
  • Electrical Engineering
Replies
2
Views
2K
  • Electrical Engineering
Replies
14
Views
5K
  • Electrical Engineering
Replies
15
Views
3K
  • Electromagnetism
Replies
14
Views
758
  • Electrical Engineering
Replies
15
Views
4K
  • Electrical Engineering
Replies
5
Views
1K
  • Electrical Engineering
Replies
5
Views
3K
  • Electrical Engineering
Replies
15
Views
2K
  • Electrical Engineering
Replies
14
Views
4K
Back
Top