FAQ: Neon transformer wiring diagram - demo fusor

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Richard Hull
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FAQ: Neon transformer wiring diagram - demo fusor

Post by Richard Hull »

Attached is a diagram on the power supply wiring for a DEMO type fusor using a neon transformer. This supply WILL NOT supply the voltage or power needed to make a deuterium fusing fusor. I show a 12 kilovolt unit in the diagram but a 9kv-15kv neon transformer will work, but the 12kv or 15kv transformers are recommended.

All neon transformers over 7.5 KV are CENTER TAPPED - CASE GROUNDED SECONDARY types. This CENTER TAP connection is made internally to the METAL CASE BODY and is the return path for the two outside HV knobs. The case is always GROUNDED for safety! The knobs, then, relative to ground, are at 1/2 of the rated potential of the transformer.

As shown, the output using a 12kv, 30ma neon transformer would be on the order of up to 10kv max with no load. With a 2ufd @ 10kv capacitor, you might expect 8kv @5ma with the voltage lower at higher plasma loadings.

The diodes can be standard microwave oven diodes. These are typically rated at 12-15kv piv @ 250-500ma. It is recommended that you use 4 diodes, (two in series for each diode symbol shown in the diagram). This will allow for some extra margin of over volt protection when using 12 or 15kv transformers.

NOTE***** The capacitor shown is not absolutely demanded in this simple supply. Consider it optional. However, with a capacitor the voltage is smoothed out and this circuit is especially lethal and can kill instantly. Be very careful to discharge the capacitor before working on the circuit. Without the capacitor the circuit can still kill in certain circumstances, but at minimum it can injure you severely and make you wish you were never born.

The digital panel meters are cheap and can be found from a number of electronic suppliers like Jameco, Marlin P. Jones, etc., for about $10.00 to $20.00 each. You will need to set the decimal point using the instructions supplied with your meter. Metering is not demanded in a demo fusor, but recommended so that you can get a feel for operation at observed voltage and current levels. This trains you for real fusion operation later and you will have to have these later, anyway, if you go beyond the demo system.

The critical 100 megohm series resistor in the voltmeter circuit is a special high voltage resistor (DO NOT USE 10 - 10 megohm common resistors in series!!!! This resistor must withstand the full voltage; common resistors will not! The proper resistor will be a long resistor, (~3" long), designed to prevent arc over.

IMPORTANT! regardless of meter type, please shunt the volt meter terminals with an NE-2 neon lamp and put it where it is visible. If this lamp ever comes on and stays on, your meter is "open", (defective), and you should immediately kill the power as touching the meter might be very dangerous with power applied.

NOTE****

It is very important to use a variac or variable transformer to supply a variable 0-120 volts AC input to the transformer's primary. This will allow a smoothly variable output DC voltage to the demo fusor ranging from 0 volts to almost 8 kilovolts. The ideal variac is capable of 10 amps with 120VAC input. A 5 amp variac is pushing it, but a 7.5 amp variac will do just fine. Note* A 20 amp variac is overkill, but if you can find one, you will be set for bigger and better experiments later on.

It is also very important that all current metering is done with a low value high wattage SHUNT resistor in the grounding circuit!!!! This is regardless of whether you use an analog or digital meter. NOTE!! The grounding of the transformer case is achieved through the current shunt resistor! If you ground the case directly, the current meter will not work.

All the grounds shown should be connected together with the shortest possible routing and this single connection taken via a short, fat cabling to the fusor chamber body and attached at the same bolt or point on the fusor chamber that your real, super earthed, electrical ground is connected to. (star grounding)

Richard Hull
Attachments
Simplest possible demo fusor supply that uses a neon transformer!  The basic supply for a beginner demo fusor.
Simplest possible demo fusor supply that uses a neon transformer! The basic supply for a beginner demo fusor.
Far more complex fusor power supply that can be used for an advanced demo fusor or, if using a very strong x-ray transformer (shown) can be used for fusion from a 60hz mains.
Far more complex fusor power supply that can be used for an advanced demo fusor or, if using a very strong x-ray transformer (shown) can be used for fusion from a 60hz mains.
fusionwiringct.jpg (45.14 KiB) Viewed 36332 times
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Henry Cross »

Hi Richard,

Is it worth using GFCI outlet or will the transformer disconnect the circuit sufficiently?

Thanks,
Henry
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Carl Willis »

Henry,

If you observe proper wiring practices, the GFCI should cause you no trouble.

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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by AllenWallace »

Richard,

I know that you are trying to keep the schematic simple and theoretical but perhaps we might add a diode across the voltage meter. If the 100M resistor arcs over, then the diode will protect the panel meter which is typically exposed to the the operator.

Its possible that someone will use common resistors which typically have a max voltage to 150 Volts. A possible but misguided design might use ten 10M resistors in series and these will arc over. Perhaps you could clarify the requirements of the 100M resistor.

Allen Wallace

Edit: I have added a note about the need for a special HV resistor in my original. RH
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by charlie_mccartney »

Sorry if this is a dumb question but if I have a NST that outputs DC do I need all of this and if this is for DC output what do I need for AC.
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by charlie_mccartney »

Also does any of this need to be immersed in mineral oil.
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Carl Willis »

No neon sign transformer outputs DC. Not all neon power supplies are transformers (NSTs) any more, but all are AC power supplies. DC ruins neon tubes.
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Richard Hull »

No neon transformer puts out enough voltage to need any form of oil immersion.

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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by charlie_mccartney »

Thank you Richard and Carl.
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by charlie_mccartney »

Would this work with a 15kv 30 ma NST and if not what would need to be changed.
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Richard Hull »

The above will work with any neon transformer ever made. I stated this in the first lines of the FAQ. Read it again.

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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Scott Moroch »

I have spent hours searching through the 15 years of history on this forum. I search a certain thing such as "spark plug feedthrough" or "neon sign transformer" and then go through every single post and response. However, I still have a few questions (probably because I am only 14 and this is the first time I'm dealing with this type of equipment).

My first question is how to hook up the 2 diodes in a series? I am probably over thinking it but I just want to be sure how to do it. Second, I'm still do not understand how to hook up the input voltage of a neon sign transformer. It is not a simply "plug into a wall outlet." I posted this same question not too long ago and was told to check the 15 years of history and FAQ's. That is exactly what I did, and yet I am still confused. While I am making this post I just have an unrelated quick question: Is hot glue air tight?

I apologize for these beginner questions however any help at all would be greatly appreciated and help a lot to getting my demo fusor up and running.

Sincerely,

Scott
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Carl Willis »

Scott,

I can understand your frustration, but let me be absolutely clear about one thing: Fusors and other line-powered high voltage gear are emphatically not entry-level projects. You are going to need help--hands-on, experienced, adult help--to hook up that neon transformer safely. Our forum is actually full of advice on how to use NSTs, but the discussions assume a passing familiarity with general concepts in electricity, like what a circuit is, how a diode works, how a transformer works, and how to attach a power cord to equipment. The best way to learn those things is not on this forum (because, you're right, they aren't discussed), but under the tutelage of a competent adult.

Please let me know when you have someone to help out.

-Carl
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Richard Hull »

I have deleted the five chatty posts after Carl's well thoughout admonition.

The rule is if you don't have anything to add in the way of correction or new information within a FAQ, please carry your discussion on outside of the FAQ in a new subject post within the relevant forum. FAQs are not a discussion forum.

Carl and all of us have stressed that each newbie be a "self-directed learner in all efforts related to those very elementary and basic things common to simple electricity and commonly understood to most amateur scientists. It is hoped that most attempting even a demo fusor would have a basic idea about simple circuits. A good amateur scientist, of most any age, should have a simple and basic underatanding of materials, chemistry, and electricity and be safety conscious. If he or she enters a realm of more complexity in one of these disciplines then they should head for a good book to bone up as needed. In this day and age, a Google search is often sufficient. Still, learning how to use and acquire a few key reference books for your own scientific library is of signal value.

Good, active amateur science demands you work with both your hands and your head.

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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by charlie_mccartney »

Hello Richard, sorry but I am not going to even try this until I fully understand what I am doing. So I have added on and I have had some very knowledgeable people on here telling me that your picture is incomplete so would this be right.

https://docs.google.com/document/d/1O43 ... 4Z-tE/edit
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Richard Hull »

It will work just fine. I did not draw the fusor. The assumption is and the hot line is marked "to fusor grid". The grounds are also obviously connected to the fusor shell which is forever grounded. Your friend just connected the obvious lines.

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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Charles Vorbach »

So no special procedures are required when attaching HV wires?
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Richard Hull »

No, not particularly. They are just wires after all. The basic assumptions are:


1. You have the supply turned off or better still, unpluged!
2. You have selected wire that is insulated to the full extent of the voltage you are going to operate.
3. You can turn a screw or bolt to attach wires or solder them.
4. When routing high voltage wires, you allow pleanty of clearance around other objects and keep all such wiring from ever being touched once in operation.

All of the above is just common sense.

Over 30 kilovolts corona can become an issue and creates its own special remediation procedures. Few who land here ever go into this range as few who land here ever actually do fusion.

The ground wires are all just normal 16 gauge of larger insulated wires with normal household wire insulation. Only the hot negative high voltage wire to the inner grid from the supply needs to have special HV rated insulation.

Richard Hull
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Matthew Michalewicz »

I have a quick question. For the voltage measuring circuit, why is the 1K resistor so precise? Will a standard 5% tolerance really have that large of an effect for measuring the voltage?
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Richard Hull »

Not critical at all if you don't mind being a couple of hundred volts in error plus or minus. This is especially true with an analog meter, but if you use the digital voltmeter,(3 or 4 digit readout), pay absolutely no real attention to or place any value in the reading of half of the trailing digits.

I had some 1% 10 megs put in series on hand and many 1%, 1k ohms so I used them. The accuracy seemed important at the time. High accuracy in HV measurement on a demo fusor is just not needed, of course.

In real fusion above 20kv, a +/- 1000 volt error in your reading is of no real significance unless one is truly, anally retentive or planning on submitting a peer reviewed paper to a major journal.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Matthew Michalewicz »

Alright, I was just making sure there wasn't anything I was missing. Thank you Richard!
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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Richard Hull »

Updated this thread with the first post's addition of the most simple possible demo fusor power supply diagram as well as a much more involved and complex hookup for those who might want to be in the plasma club with metering and filtering added and current limiting for a final supply that can even do fusion in future. July 2023

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Re: FAQ: Neon transformer wiring diagram - demo fusor

Post by Dennis P Brown »

I recently lost a HV diode in my bridge circuit (second time. Getting old. Haven't bothered to fix it with so much going on.)

Having a Neon Sign Transformer (NST) makes determining the bad diode rather simple. Just hook up one side of the NST output to my fusor input HV cable, and measure the diodes in the bridge.

So besides use as a demo power supply, a NST is extremely useful for testing very HV diodes (20 kV.) With a variac, could be used for lower voltage (1 kV and up) diodes, as well.
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