FAQ: Neon transformer wiring diagram - demo fusor
Posted: Tue Mar 02, 2004 11:38 am
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
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