switch supply without grounding, it's free energy or I pay for that?

[dxer_87]

Hi! I have ungrounded elctricity installation. Once when I did a great mess with my wires I try to find any difference of voltage between central heating pipe and wires. I found that between switched off and plugged in atx power supply chassis there is approx. 90V AC. So I tried to rectify the source and put a LED. It blinks, but only sometimes, when i.e. atx switch was on. I tried to connect a LED without rectifing diode. And it glow, hura! I then tried to connect one different way knowing the source is alternating. And it glows too - what a magic stuff I have a question of this design. When I connect the diodes, does it draw the current from installation (because it's probably true) or is it some rubbish electricity made because of switching supply and ungrounded inst. - this is probably true too. Anyway, I'm proud I did something different and ... the LED glows, o yeah (laugh). Try this in your inst, remember unground the PS, maybe will work

[mscoffman]

In this case you pay. The power supply designers tried to have the input
part of a switching power supply balanced in between the two hot and
cold wires of the utility power line. But in certain instances the AC
capacitance is not exactly balanced between the two utility wires and the
powersupply chassis ground. In most cases this imbalance causes the small
AC ground current to flow.  It's capacitive, not resistive (like water leakage is)
so that is why it is unloaded at 90VAC. In the old days the capacitance was much more
and you could easily get a shock between an equipment chassis and earth ground
hence our three wire utility plugs. Too much imbalance though will trigger
one of those special human-shock protected outlets.

The utility company could pay if you have any DC current flowing between
utility wires after you have very carefully removed the AC 50/60 hertz with
a filter. Also, the utility equipment has a finite regulation bandwidth and doing
things above that frequency can cause losses in utility equipment that might
acure to your side of ledger.

:S:MarkSCoffman

[dxer_87]

Great thanks MarkSCoffman! You instructed me very well. Good lesson. Thanks to my teachers I know what the capacitance is Eventually it shows that the design of this switching supply isn't the greatest one. I heard that all of devices that rectify pure AC without transformers are the problem with making noise in the whole installation, i.e. the CCFL compact lights. I know that only switching supply design has a good efficiency and small dimensions corelating to its high power. If this design would be a better, it wouldn't have this parasitic flow of current. I'm just thinking, if You have complete house system, is it possible to unground it at the end and use this little energy amount somehow?

In the second part as I understood, I should make a connection by a filter from ground to cold wire to cheat the energy meter? Is this right? (I know anybody shouldn't do such anyway, because it's risky!)

Przemek

[dxer_87]

Microcontroller, do you think of something like this? Any suggestion to this circuit will be well seen. Maybe different diodes for bridge rectifier?

[dxer_87]

Ok, I have such poly caps and switch isn't a problem too. You have mentioned 555  or a microcontroller to discharge the cap at a threshold. In this point I would probably crack without any circuit shown. Anyway, I'll try this to see if I have enough energy in aether around my house to glow for free a LED

Przemek