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do I need to isolate a negative ion generator?

I am looking to build a negative ion generator based spark gap... I need to limit dielectric loss, and need to use 8" of small gauge wire to and from the switch to turn it on. do I need to isolate the switch electronically from the rest of the circuit? if so, would a reed relay do the trick? if I use a reed relay, could I run it from the same power source, in parallel, or do I need to isolate power sources as well? my setup will be slightly similar to the Electrifried shoe diagram below. (no, that's not the project)

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NachoMahma8 years ago
. Unless one side of the switch is bonded to the case (of the sw) and you mount the switch so the case becomes part of the circuit, you'll be OK. It's just a "master sw" for the low voltage side.
gschoppe (author)  NachoMahma8 years ago
two related inquiries... 1) doesn't an equal voltage differential (with absolute respect to ground) exist on both sides of the generator? 2) wouldn't I lose effectiveness if I run longer wire between the generator and the positive side of the spark gap? 3) isn't small gauge wire at risk of melting with a high return voltage? 4) if I did isolate anyway, could I run off the same battery, or would I risk shorting the generator?
1) Not sure exactly what you mean. If you mean "Do they have a common ground?" (which may not necessarily be at Earth potential), ie, -9V = HV ground, then not necessarily. My guess is that they have a common point inside the generator, but the 9V side doesn't require an Earth ground of any sort.
2) You are transmitting voltage, not current, so wire guage is not that important. There will be some current flow, so there will be some voltage drop, but, 8" shouldn't be a problem at all. Insulation will be more important, the poorer the insulation the greater the losses with longer runs.
3) Voltage doesn't melt wires, current does. The output of the generator drops quickly with a load. It shouldn't put out enough current to worry about. If melting wires are a problem, you're gonna kill somebody. ;)
4) Not sure I understand, but the HV side and the LV side are isolated by the stepup circuit. Whether or not one side of the 9V is grounded shouldn't affect operation. Since I don't understand the question, I don't have much confidence in that answer.
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. The only "ground" you need to worry about is the one between the generator HV side and the shockee - the environment will often take care of that. You only need to isolate (keep above ground potential) the "antenna."
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. If that doesn't answer your questions, try to amplify on 1 and 4.
PS: It may help if you think of the generator as a transformer (ignore the AC/DC part). The antenna is one leg of the secondary.
gschoppe (author)  NachoMahma8 years ago
in that case, isn't the battery's positive terminal connected directly to the other leg of the secondary? (there are only three wires involved) what worries me is my implementation... 1 I'm not zapping people, I'm going to connect the "earth ground" wire from the diagram to one side of a spark gap, rather than earth... the "body contact" wire will be connected to the other side, rather than my body... I'll be using a small tach switch to trigger it, and I don't want to make myself a part of the circuit... 2)i am charging whatever surface I use, in a similar manner to what a vanDeGraff Generator does... wouldn't I end up with a relatively high amperage when the spark "gaps"?
. <blush> For some reason I kept seeing the foot plate as a switch. It does appear that the LV and HV sides have a common "ground."
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1) If you connect the foot plate to Earth ground, your body will see no more than 9V.
2) Only if you add enough capacitance to the circuit to store a large charge. Even then, the current flow will be between the capacitance and Earth.The NIG itself doesn't put out much current.
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. The power (volts * amps) on both sides of the circuit will be the same. If the output voltage is 2x the input voltage, then the output current will be 1/2x of the input current. You are stepping up the voltage by a factor of ~1000, so you only have ~.001 of the current a 9V battery can supply at the output.
gmoon gschoppe8 years ago
1) Unless the secondary has a center tap, it probably doesn't swing plus and minus relative to ground (and how can we tell, from that diagram?)

In any transformer circuit, you decide where the potential is connected--much the same as connecting batteries in series. Do I add the next battery on the positive end of the chain, or the negative end? After all, you can add transformers in series, just like batteries.

You don't have the choice with an autotransformer (which it probably is), because the primary and secondary aren't isolated. But you don't usually see a center tap on an autotransformer.

Also--I'd question using the plus terminal as the earth gnd. In every neg ion generator schematic I've looked at, there's a typical circuit gnd wired to the negative side. Unless a negative PS was specified, you could blow the circuit.

If you've wired it way thinking you'll get maximum voltage differential between the output and the ground, you'd only gain 9V...(and the output is measured in KV, right?)

in that case, isn't the battery's positive terminal connected directly to the other leg of the secondary? (there are only three wires involved)

Or the negative terminal. Just because it's negative ions doesn't indicate if it's a negative voltage PS. If it's a transformer-type circuit, it's probably an autotransformer (single coil) and the primary and secondary grounds are the same. But which is the gnd reference? I don't know.