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Where do people get a high voltage power supply (about 300V) cheaply?

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Yanom

Sat May 26 2012, 02:30PM

Registered Member #4659 Joined: Sun Apr 29 2012, 06:14PM
Location:
Posts: 158

Hi, I'm a high school student trying to build a coilgun. I recently found out that the caps used in most coilguns are photo flash caps in the 200V-400V range. Where do you get the power supplies to charge these things? I don't have very much money, so currently my electrial expermients have been using for power supplies old AC/DC converter wall plugs like this:
Sps1212 Large 50770 Zoom

It outputs 12VDC (0.2 Amsp) at that plug. I cut off the plug tip and got two wires I could hook aligator clips to. It works, and if i put multiple in series (there were a bunch of old ones lying around the house) I could get higher voltages. But how will I get the 300 volts needed to charge photo flash caps? Looking around, high voltage power supplies seem to be >$1000

Thomas W

Sat May 26 2012, 02:48PM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
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Posts: 1276

you could get a isolation transformer and make it to a buck-boost style by connecting both sides together in series to get 220v if your in america, or 480v in england, another way is to get a 240v->110v site transformer and do the same thing for 350v,

im currently using a large 3.3Kva site transformer, i also have a 240v -> 50v i can buckboost to do the same thing.

~~~Thomas~~~

Ben Solon

Sat May 26 2012, 04:17PM

Registered Member #3900 Joined: Thu May 19 2011, 08:28PM
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Posts: 600

mains voltage multiplier, boost converter, zvs transformer, etc.

there are many ways to do it, and it depends on how fast you want to charge it, and how large it is. usually i just charge to 340v by using an auto-transformer and a bridge rectifier. its extremely fast(a couple ac cycles). if you wanted higher voltages, you would need a different transformer. i would use this:

for general use.

Dri0m

Sat May 26 2012, 05:16PM

Registered Member #4497 Joined: Thu Apr 19 2012, 12:53PM
Location: Behind you
Posts: 62

i build ZVS, get ferrite from DST and measure voltage/turn ratio, then it's simple :)

Marko

Sat May 26 2012, 07:27PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hi,

Well I have no idea why every coilgun builder simply refuses to use mains for their power supply, which is already perfect voltage and lots of power. Just remember to limit the current by some sort of a heater, light bulb, inductor, capacitor, etc...

If you are in US, then you can use a smaller doubler caps (such as motor run caps) which would act as current limiters in that case.

Marko

radiotech

Sat May 26 2012, 07:44PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

The mains can supply ample reserves for a coil gun, but the construction
techniques have to comply with certain safety rules and must not disturb the
network.

Steep charge rates throw flicker components on to the power line.

The other thing is, some builders may be young and might be limited to
what they can do in their homes.

Perhaps the test for the older builders of gigantic home projects is they
haven't burnt the place down, and they are still alive.

Neet Studio

Sun May 27 2012, 01:59AM

Registered Member #4037 Joined: Fri Jul 29 2011, 03:13PM
Location:
Posts: 86

There is always the original charging circuits on the camera. ;) It is already there for that purpose and a bit slow. Use a rechargeable battery or D cell and it would work better.

Beyond that, some DIY design/construction skill is required. Even using old adapter transformer backward with a push/pull transistors pair driving the secondary and rectifying the AC from the primary would get you there.

Always be careful about safety around charged high voltage capacitors, it is a great way to DYI (Do Yourself In).

Yanom

Sun May 27 2012, 06:36PM

Registered Member #4659 Joined: Sun Apr 29 2012, 06:14PM
Location:
Posts: 158

Neet Studio wrote ...

There is always the original charging circuits on the camera. ;) It is already there for that purpose and a bit slow. Use a rechargeable battery or D cell and it would work better.

So these are DC to DC voltage step up circuits? Also the slowness is good, that means low current so I'm not likely to hurt myself.

genious 7

Sun May 27 2012, 09:43PM

Registered Member #2887 Joined: Sat May 29 2010, 11:10PM
Location: Panama City, Panama
Posts: 107

Cheapest way would be a voltage doubler in the US or a simple rectifier in Europe. You would need only a four diodes if Europe or two diodes and two caps on US. Additionally, a high-wattage resistance or a light bulb to act as a current limiter and the mandatory fuse.

So these are DC to DC voltage step up circuits? Also the slowness is good, that means low current so I'm not likely to hurt myself.

If charging a large capacitor bank, you still need to be careful because of the stored energy.

Yanom

Sun May 27 2012, 11:08PM

Registered Member #4659 Joined: Sun Apr 29 2012, 06:14PM
Location:
Posts: 158

wrote ...

There is always the original charging circuits on the camera. ;) It is already there for that purpose and a bit slow. Use a rechargeable battery or D cell and it would work better.

Got one.

wrote ...

Always be careful about safety around charged high voltage capacitors, it is a great way to DYI (Do Yourself In).

Indeed. I accidentaly touched two (random!) electrodes inside when taking the cover off and shocked my finger. I'm going to wear gloves from now on...

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