# Building a capacitor bank for railgun project

Discussion in 'The Projects Forum' started by EPond89, Mar 14, 2012.

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1. ### EPond89 Thread Starter New Member

Mar 14, 2012
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Hi,
For my physics 2 class our group has decided to build a rail gun. I went to my local Walgreen's and asked for used disposable cameras and the guy was glad to get rid of 20 and give them to me. I researched what "general" specifications for flash capacitors was and it was 330V and holds 270 uF. Before i go about building this bank I have a few questions.

1) From what I understand, you can add capacitors in series to increase the potential difference. ie. for 2 330V capacitors hooked up in series would be capable of 660V and would hold still 270 uF. My question is that I've heard to be careful and not exceed a capacitor's voltage rating. Is this considered "overloading" the capacitors voltage rating since the bank will be be trying to achieve a max of 660V?

2) Assuming that (1) will not overload the capacitors, what voltage is best to operate a rail gun at, Ive heard that "high-voltage" is best, and Ive seen most around 400V. It seems pointless to hook up 2 capacitors in series to gain this 70V of potential difference, would it be useful in trying to achieve a greater voltages (ie. 500 or 600)? and would I even want to get to 500 or 600 Volts.

3) My goal is to eventually get a semi-large bank with these capacitors having all 20 of them used in the bank. Ive thought of two configurations, one only being possible if (1) will not overload the capacitors.
1) (660V) to have 2 sets of 10 capacitors. Each individual set will be hooked up in parallel acting as a single capacitor, and then in series with each other. The outcome bank (correct me if I'm wrong) would be 660V and 2700uF.
2) (330V) to have All 20 capacitors hooked up in parallel. The outcome bank would be (again, correct me if I'm wrong) 330V and 5400uF.
Which would be more optimal? I will NOT go strait into building the full bank, will probably try 6 first and work my way up as I get more comfortable.
3) I'm not sure if all will be rated exactly the same. If some were rated at slightly different voltage ratings and capacitance ratings does this affect my configuration?
4) I was going to use a voltmeter to measure the Potential Difference when charging the capacitors, what is the best way to go about charging a bank like this? Ive heard that by using a singe camera circuit you can achieve this, but at slow rates... what would be a good (preferably cheap) way of going about this?
5) I've heard of capacitors sometimes discharging at the switch. How do I prevent this?
6) (MOST IMPORTANT) How do I safely discharge a bank? What important safety precautions should I take when building this.

*edit, I don't think I did the math right for the Capacitance values in the circuits, I'm late for class and will do them when im out.

Thanks

Last edited: Mar 14, 2012
2. ### R!f@@ AAC Fanatic!

Apr 2, 2009
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And Good Bye.

3. ### hwy101 Active Member

May 23, 2009
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Rifaa, you forgot something

6. Restricted topics. The following topics are regularly raised however are considered "off-topic" at all times and will result in Your thread being closed without question:

• Any kind of over-unity devices and systems
• Automotive modifications
• Devices designed to electrocute or shock another person
• LEDs to mains
• Phone jammers
• Rail guns and high-energy projectile devices
• Transformer-less power supplies

4. ### John P AAC Fanatic!

Oct 14, 2008
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Yup, no rail guns. Thread will be blasted into space any moment.

Apr 5, 2008
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Hello,

I am closing this thread as it violates AAC policy and/or safety issues.

Quote:
6. Restricted topics. The following topics are regularly raised however are considered off-topic at all times and will results in Your thread being closed without question:
Any kind of over-unity devices and systems
Automotive modifications
Devices designed to electrocute or shock another person
LEDs to mains
Phone jammers
Rail guns and high-energy projectile devices
Transformer-less power supplies
This comes from our Tos: