Charging / Electromagnetic Projectile Accelerators / Forums

Forums

4hv.org :: Forums :: Electromagnetic Projectile Accelerators

« Previous topic | Next topic »

Charging

Move Thread

LAN_403

Via

Thu Sept 09 2010, 01:22PM

Registered Member #3179 Joined: Thu Sept 09 2010, 01:12PM
Location:
Posts: 2

After 3-4 years out I've decided I want to build another coil gun but all the pieces to my old one got left at Ex's after we split so no doubt in a tip by now.

Will probably be running 4 caps of 470uF @ 350v. 2 in series, 2 in parallel giving 940uF @ 700v.

My initial one started with flash camera chargers but quickly became a bore waiting 10mins for a charge when I broke out the bigger caps so after a failed attempt at building a boost charger which was diagrammed on anothercoilgunsite I purchased a prebuilt one direct from him and it worked great but the site seems to have died now and theres no longer a forum and I doubt I can get one again.

Does anyone know any decent diagrams for building a decent charger? is an oscilloscope crutial to building one? preferably want the charger to be running of 12vdc either through a mains transformer or a SLA battery.

DerAlbi

Thu Sept 09 2010, 03:19PM

Registered Member #2906 Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727

Your capacitor configuration will end up in 470uf

Think about it. Serial connection halfes the capacitance, paralleling will double the half. 2*0.5 == 1

Charging: you may look at my thread here

there are photos of a charger that operates with 4x 450W PC-Powersupply transformers driven by 2 fullbridges. gives about 450V (if i would not regulate) out of 12V input. Charges 54mF to 350V in 11sec. (if my software would not regulate the inputcurrent to its configured maximum of 30A currently so it needs 15sec @ 60% efficiency)
For you probably a similar configuration with only one transformer would do the job. The Fullbridge is needed to double the input voltage. I have connectd 2 Transformers in series to reach the voltage. For you i would recommend to put 2 transformers in series, but with the meaning that the output of the first transformer wil supply the input of the next transformer. This configuration should work up to your desired voltage.
However if you are not able to create a circuitboard or the schematics for that by yourself you should probably use a commercial solution.

Simple stepup converters will not for this voltage ratio (900:12) you will need kind of a transformer (if you are not willing to wait)

woxxey

Thu Sept 09 2010, 03:37PM

Registered Member #1906 Joined: Sat Jan 03 2009, 05:06PM
Location:
Posts: 39

This is the charger I'm using and it has been working fine for me. Might be a problem to get it to charge up to 700v though. Uzzor states a power output of 15W and the author of this site claims to have achieved 25W output.

Dave Marshall

Thu Sept 09 2010, 04:13PM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

DerAlbi's solution will work, but it's seriously overkill for this purpose.

I always liked a Variac controlled MOT with a nice beefy bridge rectifier and a big honking (low value, high power) resistor on the output for a bit of current limiting. This will give you ~150V-2KV output with careful selection of your bridge rectifier, and at significant current for quick charging. This charger will primarily be limited in power by your variac and the resistor, but can easily approach 1KW output.

-Dave

Via

Thu Sept 09 2010, 04:52PM

Registered Member #3179 Joined: Thu Sept 09 2010, 01:12PM
Location:
Posts: 2

Don't really want to be tied to mains, even though I doubt it will ever leave the shed, I want to make a portable (albeit heavy) version in the long run.

This is the schematic for original boost controller, seems similar to one woxxey posted,

There is one for a version 3 now which has a voltage control (original had to keep eye on multimeter)

Dont know why the one I originally built didnt work, unfortunately whilst I can follow a schematic and copy it when it didnt work I didnt have a clue where to start.

Think I will give the v3 a try if I can source all the parts, maplins has got dreadful recently :( does anyone know a better UK place for getting parts?

DerAlbi

Thu Sept 09 2010, 08:59PM

Registered Member #2906 Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727

Yes my solution would be overkill

But its verry simple to use and to build..
Its a simple NE555 with a mosfetdriver like IR2184 driving 2 IRF1404. The rest depends on the right winding configuration.. and of course the rectifierdiodes that need to withstand 2kV. To limit current spikes a large inductance should be used at the secondary side. Maximum power output is chosen by the NE555 switching frequency.
All in all its not that hard to build... and it guaratees power..

ElectronicBob

Fri Sept 10 2010, 11:58AM

Registered Member #2973 Joined: Tue Jul 06 2010, 01:13PM
Location: Leeds UK
Posts: 9

Farnell is a good place to buy parts from. Don't go to maplin...they tend to be overpriced.

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob