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 #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
i was wondering, would these be good for a coilgun?
or
this one seems too cheap for 850 joules, any comments?
I think that the ESR is low, but im not sure. When they say shelf life 1000hr. Does that mean itle only last a month and stop working?
On a saftey sheet for capacitors, it says frequent charge and discharge load via low resistance can cause the capacitor to drop in capacitence or be destroyed. Is it Ok for coilguns? or should a different cap type be used?
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Shelf life is normally not specified. What is specified is the lifetime under a certain load and temperature.
The lifetime is considered to be over when the ESR has increased by some amount (for eample 50%) or the capacity has been reduced by some amount (for example 15%). A capacitor will gradually degrade with time but will generally not suddenly stop working unless you abuse it badly.
High voltage and high temperature speeds up the degradation dramatically. When you discharge it and store it at a normal temperature the degradation stops and it will last almost forever.
Most coil guns are not fired very often so this type of capacitor usually works fine. I have some that look similar that are 20 years old and still usable even if they have reduced capacity.
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
How often is often? =)
This is for a project, so coil size, projectile, and other variables will be changed, so it will be fired a fair amount of times. Will it help if i put the caps in a ice bath?
What size projectile should i use for 500J? 1kJ?
For the diode to protect the caps, where can i get one with that high of a rating? A bunch of cheap ones is preffered =). What about a SCR, will a hockey puck one be required?
Edit: what kind of current peak can i expect from this? on the diode string tutorial, it says it can stand up to 30A peaks. 1N4007 are rated for 1 Amp, does that mean for short periods it can stand higher currents?
Excuse all my questions, dont want to waste a bunch of money =p.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
The old Sprague 36D-range of electrolytic capacitors are excellent. I have some that are over 30 years old and still have reasonably low esr. The 36D range are very reliable and long lived.
For really low esr you need the modern 'Inverter Grade' capacitors preferably the 105 degrees C type, LL (long life) types are best for long life (doh!)
Registered Member #32
Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549
How often is a CG fired? Depends. If you're just a hobbyist, chances are you'll only fire half a dozen times at most before adding some new feature. If you just want a real projectile flinger I guess you might do more.
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.
A couple of questions about capacitors
