If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #1056
Joined: Thu Oct 11 2007, 11:15PM
Location: CT, USA
Posts: 27
How come no one has Used Super Caps In a Coil Gun Yet? By Super Caps I mean the 5.5V 1Farad Kind, like these:
I was going to buy a couple for a portable one I want to make, but figured Id get some opinions first.
If that doesnt work, I do have a backup plan, in which I have 50 1,000uF Caps rated at 50V Each. (which equates out to 62.5 J Total). If I got 10 of those 1 Farad caps, and ran them at 5V Each, that would equate to 125J And In about half the size of the caps I have.
Registered Member #16
Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554
Those capacitors are designed for memory backup and low current power supply filtering. They have extremely high ESR (Equivalent Series Resistance), and cannot source more than a couple amps. They also like to self destruct when run into a dead short, and because of their low tolerance for abuse, would almost certainly be destroyed in the first few shots by the inductive 'kick back' generated by the coil.
Car audio capacitors are better suited (built for rapid discharge and recharge) however they have a very low energy density, and are quite expensive. General purpose 'computer grade' electrolytics, and more so inverter grade 'lytics are far better suited for such a purpose, and are much more economical and practical.
Your 1,000uF 50v caps could work, but I'd recommend not putting them all in series. You'd probably get a higher peak discharge current with a combination of series and parallel (referred to as a cube configuration), as this would help reduce the ESR of the bank overall. Probably something like 5 in series, then ten banks in parallel.
Alternatively, I've got several dozen 250V 680uF caps here gathering dust. They're about 21 Joules a piece. If you're interested, PM me with your mailing address and I'd be happy to throw 10 in a box and send them your way.
Registered Member #1056
Joined: Thu Oct 11 2007, 11:15PM
Location: CT, USA
Posts: 27
= Dave Marshall wrote ...
Posted: Thu Oct 11 2007, 08:02PM Those capacitors are designed for memory backup and low current power supply filtering. They have extremely high ESR (Equivalent Series Resistance), and cannot source more than a couple amps. They also like to self destruct when run into a dead short, and because of their low tolerance for abuse, would almost certainly be destroyed in the first few shots by the inductive 'kick back' generated by the coil.
Car audio capacitors are better suited (built for rapid discharge and recharge) however they have a very low energy density, and are quite expensive. General purpose 'computer grade' electrolytics, and more so inverter grade 'lytics are far better suited for such a purpose, and are much more economical and practical.
Your 1,000uF 50v caps could work, but I'd recommend not putting them all in series. You'd probably get a higher peak discharge current with a combination of series and parallel (referred to as a cube configuration), as this would help reduce the ESR of the bank overall. Probably something like 5 in series, then ten banks in parallel.
Alternatively, I've got several dozen 250V 680uF caps here gathering dust. They're about 21 Joules a piece. If you're interested, PM me with your mailing address and I'd be happy to throw 10 in a box and send them your way.
Dave
Wow thanks a lot! Luckly I can Generate Somewhat high voltage using a 555 Timer. This is how I was getting 50V from 5V. I'll have to make a bigger inductor for larger voltages. I was going to put the whole bunch in parallel, since I figured there would be lower ESR.
I used the circuit from this site and just put in my own values. The Inductor I used was actually a Test Coil, made of 17AWG Wire. Total Inductance was 7.22uH (estimated). So 250V Shouldnt be that hard to get to. How big are The caps? Are they small or Jumbo Sized?
Playing with Numbers, It seems I get the same Energy No Matter which Combo I use (more or less).
Banned Registered Member #110
Joined: Fri Feb 10 2006, 12:23AM
Location: Banned City
Posts: 85
How come no one has effectively used...? is a better question. People have neither not known about nor decided to not attempt. People simply have come to realize after making attempts that its a lost cause.
The super caps do not meet the current requirements. Just as car batteries are not AA cells, coil guns do not use 5.5v 1 Farad super caps. The max discharge current is no where near high enough for high current applications.
Registered Member #1056
Joined: Thu Oct 11 2007, 11:15PM
Location: CT, USA
Posts: 27
= rupidust wrote ... How come no one has effectively used...? is a better question. People have neither not known about nor decided to not attempt. People simply have come to realize after making attempts that its a lost cause.
The super caps do not meet the current requirements. Just as car batteries are not AA cells, coil guns do not use 5.5v 1 Farad super caps. The max discharge current is no where near high enough for high current applications.
How come I need to tell you this?
Truthfully I didnt know this. I figured all caps are equal in charge and discharge despite their capacitance rating.
Registered Member #16
Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554
In his defense, I will say that specs for surplus caps in general, but particularly super caps as seen on most sites like Alltronics and Electronics Goldmine are damn hard to come buy. They provide few details. A model number if you're lucky, and maybe even a manufacturer, but its a crap shoot.
I've attempted to find info on those caps for other projects, and was thoroughly frustrated.
Registered Member #1056
Joined: Thu Oct 11 2007, 11:15PM
Location: CT, USA
Posts: 27
There are Specialty Caps That are used For high Energy Apps (such as pulse power) But a .5F Cap goes for about 17 bucks!!! Totally not Worth it...For that much I can probably get a couple 400V Caps from One of the Surplus Sites.
Is there an Upper Limit For The size of the Coil? Im going for Single Coil since it would be easy for my first time Around. I actually un-wnded a MOT and got the wire from there. One hell of a PIA! But the wire is in good condition, and the Microwave was working. There was a bit more than 1Lb Of wire.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Have a look in the wiki and the archives, almost all sensible questions about simple coil guns are answered there in one way or another.
Making a coil gun is simple, making an optimal coil gun is difficult. The general consensus is that you should just make one and experiment with different configurations of capacitors and coils. That way you will learn efficiently and discover many things you would never have thought about.
You should also put some effort into measuring the projectile speed accurately so you can judge your progress.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Super Capacitors
