Hi Mike You wrote:
> If you think you are safe, you might be in for a bad surprise. It >doesn't matter which way you plug your circuit in. With a bridge >rectifier, both rods have the same shock hazard. >Here is an animation of a bridge rectifier that I posted earlier >that shows the voltage across the rods and to ground. >(The green arrows show conventional current flow, which is from >positive to negative. This is the opposite direction from the flow >of electrons.) >http://engineering.dartmouth.edu/other/3Dcircuits/animations/bridgeR.html >Study this graphic carefully. If you don't understand it, please let >me know and I'll try to help. >In any event, I'd abandon the circuit you are now using. >Mike Monett That is a neat graphic Mike. I agree with your point about polarity, I should have explained what I meant with shock protection. Shock hazard has little to do with voltage and everything to do with current. If you consider the circuit I described with the bridge rectifiers and current limiting resisters, with a 15k ohm bleeder resister the open circuit voltage will be 55 volts.You can take both silver rods in your hands (even wet hands) and not get any shock when handling because of the current limiting resisters. The maximum current flow through your body is likely less than 1ma. Now take a worsed case scenario; I have seen many diodes short circuit when exposed to lightning or line voltage surges. Imagine then the diode in one AC line shorting to the B+ side of the bridge. Another diode on the other side is shorting to the minus side of the bridge, the other two diodes are open. You now have 115 volts AC on the DC side of the bridge. This is where the polarity reversal becomes an issue. If a person was to hold one rod in one hand and touch a water pipe or any other type of ground, he would be exposed to approx. 40 volts AC with one polarity and about 80 volts AC the reverse polarity. However, if you consider the body resistance to be 100k ohms, your maximum current that can flow is limited to 1ma. This is very safe. I have in fact grabbed the rods and played around with conceivable scenario's, in the shorted diode case you will get a slight shock if you take the 80 volt rod in one hand and the other hand on a natural ground, but even here the current will still be so low that it cannot harm you. With the bridge rectifiers in tact, I did not get any shocks until I increased the bleeder resistor to 27K ohms. Even then just a little tickle. So I repeat, This circuit is very safe although not as safe as when you use an isolation transformer. . I should mention that I make all of my CS with 25 kv HVAC, and have been doing this for three years. Talk about a shock hazard. My reason for playing around with this circuit is because I enjoy experimenting with LVDC. I have been intrigued by Ole Bob's experiments and try to copy some of his experiments. I am also looking for a very inexpensive circuit that can I can afford to give away to people in poverty situations.
