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 I need smart people to help me make something!

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vacuum tubes tesla coil



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PostSubject: I need smart people to help me make something!   Tue Oct 19, 2010 7:47 pm

This is what I need, a variable power supply that can be ranged from 0 volts to 500 volts. This is at 1 amp or more. It must run off 120 volts, and be AC

Paul
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Tom Bavis



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PostSubject: Re: I need smart people to help me make something!   Tue Oct 19, 2010 7:51 pm

For AC, you just need a step-up transformer (120 : 500) and a variable transformer (Variac).
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Dale Saukerson



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PostSubject: Re: I need smart people to help me make something!   Tue Oct 19, 2010 8:16 pm

Please tell us what you are using this for.
500 volts @ 1 Amp is 500 watts---A pretty hefty power supply wether AC or DC.
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radiotechnician



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PostSubject: Re: I need smart people to help me make something!   Wed Oct 20, 2010 12:18 pm

The very smartest people need to be paid money even to find out if they can help you.
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pixellany



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PostSubject: Re: I need smart people to help me make something!   Wed Oct 20, 2010 12:43 pm

There are some transformers here that will get you close---if you use them with a variac that goes to ~120% of the line voltage:
http://www.surplussales.com/Transformers/HvLvTr-2.html

For 500 watts out, I'd use at least a 10-amp variac.

The whole thing is going to run around $100-150. Now the only remaining question is:

WHY?????
.
.
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vacuum tubes tesla coil



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PostSubject: Re: I need smart people to help me make something!   Wed Oct 20, 2010 1:11 pm

I'm testing the voltage ratings of diffrent borax rectifiers. I've changed my mind, no I'm going to do 250miliamps. A question, what is the minum current needed for a borax rectifier? You know, below a certain current or votage, it stops rectifing
Paul
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oldradiospook

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PostSubject: Re: I need smart people to help me make something!   Wed Oct 20, 2010 1:22 pm

Paul,

You aren't making boom boom toys are you?

borax rectifier, water rectifier, magnetic rectifiers?

Porcelain bowl rectifiers.

Heres where I flag the NSA on you.

This thing is not a
bomb is it?

Word bomb. coded and recognized. zzzz. Fortune NSA
XXXX noted 102010
activate Umbra......XXXXXX end
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vacuum tubes tesla coil



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PostSubject: Re: I need smart people to help me make something!   Wed Oct 20, 2010 5:01 pm

no, what's a mag. rectifier?


how's the chimp. eh?
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mhallack

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PostSubject: Re: I need smart people to help me make something!   Wed Oct 20, 2010 5:30 pm

I can make you a peanut butter sandwich!! Anything more technical than that ask Wyatt!!
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Gary Tayman



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PostSubject: Re: I need smart people to help me make something!   Wed Oct 20, 2010 6:21 pm

For smaller current, why not pick up one of those Heathkit Power supplies?

I bought one of these (PS-3) at the swap meet in Atlanta. Cost me a whopping $3. It was dusty dirty but it cleaned right up. I have yet to turn it on, but I'm figuring on replacing those electrolytics. It provides 0-500 volts DC, plus 6 volts filament.
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terrydec

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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 10:24 am

Sounds to me like he's building a flux capacitor. I built one but it only got me 10 minutes into the future, (I had to use '78 Dodge instead of a Delorean). I make a lot of money on horse races.
Wink
Terry
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Alan Douglas



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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 12:53 pm

I'm not sure there is any minimum for a chemical rectifier, though its self-capacitance might be a problem at very low currents.

If you really wanted several amps, your best bet would be an industrial step-down transformer, 240-480 primary, 120-240 secondary. Use the secondaries in parallel as the primary, and the primaries in series for the secondary. That will get you 120V to 480V. For lower current, an old TV power transformer. I might have something, but shipping's a killer.
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vacuum tubes tesla coil



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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 1:30 pm

I think I will use 0-500 AC @ .5 amps. Sounds good? A tv transformer could do that.

PAul
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Johnnysan



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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 1:40 pm

Most TV transformers might be able to deliver 200 to 250ma, not 500ma at 500 volts.
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vacuum tubes tesla coil



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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 1:51 pm

Ok, thanks.

Also johnny, this thing needs to consume 250- 125 watts all the time, regardless of voltage. Will a thermister do the job?
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pixellany



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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 2:14 pm

Paul;

First, did you ever look at the site I linked? There are quite a few transformers that would meet your requirements.

What are you referring to with the thermistor? Where and how would you be using it?
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Reece

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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 3:57 pm

Are you building what they used to call a slop rectifier? Common during the early tube age. I made one once in the fifties. Four mason jars with borax and water, dissimilar metal electrodes, hooked up in a bridge circuit, fed right off the 120V power line. It worked. Anybody else ever build one?

Reece
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vacuum tubes tesla coil



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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 5:10 pm

I looked, do you know how much shipping would be?

about the thermistor, the rectifier would need a load that would consume 0.25 amps all the time, right? So, I would think a thermistor would do the job, am I wrong?


also, yes i'm making a slop rectifier.
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Alan Douglas



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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 5:30 pm

If you need a load of 0.25A at 500V (and I'm not sure why you think you do) it will dissipate 125 Watts. That's a sizeable power resistor. Thermistors are generally much smaller devices, which change resistance with temperature. Sized correctly they provide a soft start if wired in series with the primary, but they have no use as load resistances.
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vacuum tubes tesla coil



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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 5:41 pm

well, alan, I'm open to ideas, what would you do? scratch I'm lost.
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bgadow



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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 8:49 pm

If you can't source a TV transformer elsewhere, let me know. There are several in the attic from 70s solid state consoles, pretty good size but not sure of their ratings. I think one of the mystery boxes I have packed has a transformer in it from an old bw set, if I haven't already mailed it off to somebody. I'm guessing bigger=better?
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Alan Douglas



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PostSubject: Re: I need smart people to help me make something!   Thu Oct 21, 2010 9:34 pm

Quote :
well, alan, I'm open to ideas, what would you do? I'm lost.

Honestly, that's what worries me. Most of us older members have played around with projects that could have gone wrong or actually did so, and survived, but then if we hadn't we wouldn't be posting here now. You don't hear from the ones who weren't so lucky. Running a few amps at a few hundred volts through jars of borax solution has the potential (sorry) of creating some interesting side effects, ranging from boiling liquids and broken glass to lethal electricity where you don't want it. We have no way of knowing your situation and capabilities, from the other side of a computer monitor. Trial-and-error learning can be effective but does have its drawbacks.

There was a very instructive discussion a few years back on the Forum, of dumb things we did as kids.
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vacuum tubes tesla coil



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PostSubject: Re: I need smart people to help me make something!   Fri Oct 22, 2010 1:05 pm

well I know what I'm doing, it's just that i'm not quite sure of the amps needed. would 100 miliamps be enough? or is 200 a better choice? also, what kind of load would be best? something that would allways consume 100, 200 miliamps, no matter the voltage?
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pixellany



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PostSubject: Re: I need smart people to help me make something!   Fri Oct 22, 2010 3:06 pm

vac*;

I don't think anyone here knows enough about your project to be able to conclude that you know what you are doing. Unfortunately, the data you have provided suggests that there are some fundamental things you do not understand.

For starters, you stated at the beginning that you needed 500 volts at ~ 1 amp. Now you are asking US whether 100 or 200 MILLI-amps might be enough!!

As for constant current, it's relatively easy to do in the supply side---for DC. I think a constant-current regulator for AC is bit more difficult.

Finally, have you worked throught all of the calculations on what happens when you pass a certain amount of electrical power thru a fluid. For starters, how fast does the fluid heat up and what gasses are released?

If you do not have the right theoretical background, then the best thing may be to try some small-scale experiments---ie small amounts of liquid, and low voltages and/or currents.

Regardless, if you share with us what is your education and training, we might be able to related better.
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