Max GND Voltage

Hi, I can't find that info. I've checked the datasheet, but maybe I'm missing something.

I will operate my Atmega32 floating. The GND pin will be connected in a higher potential.

Example: GND 100V -- Vcc 105V

My question is: how high I can go with GND potential?

Voltage is relative, so long as there's 5V between Vcc and GND the thing works.

Once you have dangerous voltages on the supply and ground you need to consider safety, isolation, etc.

And of course to a circuit running at +100V, earth potential is GND-100V, relatively speaking, and instant destruction to the thing.

Once you are several kV above earth potential you'll need to worry about corona discharge and such effects, but that's not recommended(!)

The Arduino will only "see" 5V. The danger is to you (or other humans) if you touch the Arduino ground and earth ground at the same time, or to your computer if you plug-in the USB, etc.

...It would be illegal to see a product like that unless it's insulated and encapsulated, and of course development, & debugging is dangerous.

MarkT: Once you are several kV above earth potential you'll need to worry about corona discharge and such effects, but that's not recommended(!)

That is the point. How much? How much voltage should I consider to be hazard connecting to the ground before electric field or capacite coupling become worrisome.

Rather than asking how high you can go..... you can tell us how high you want to go.... and why?

The other issue will be ensuring at 1kV, that Vcc is at 1.005kV. Do you have a voltmeter with that kind of resolution? Not to worry, the magic smoke will tell you when you have too much differential.

P.S. you won't be able to connect the laptop to the usb while it is connected.

That is the point. How much? How much voltage should I consider to be hazard connecting to the ground before electric field or capacite coupling become worrisome.

Does [u]this[/u] help?

100V is less than the voltage in house wiring so "normal wiring practices" are fine without any special precautions. Just make sure people can't touch it!

P.S. There is PROBABLY A BETTER WAY of whatever you are doing! Perhaps you should tell us what you are doing...

Not sure, but, wasn't it the amps being dangerous and not so much the volts?

I remember back home on the litle island of CuraƧao, two electricians discussing the more "dangerous" part of their job being the 110v (American) or the 220v (European) system. One said 110 is only "tickling", 220 will hot you hard. The other one said, to have the same wattage you'll need more amps on the 110 so that one will keep you "hooked". I wad never sure of their schooling and abilities, it's still a small island....

There is no need to run your Arduino at line voltage - it makes no sense anyway as the supply is AC .

Not sure, but, wasn't it the amps being dangerous and not so much the volts?

Yes, but current, voltage, and resistance are related by [u]Ohm's Law[/u]. A car battery is capable of hundreds of amps, but 12V through the resistance of your skin/body only results in microamps so you can't even feel it. (You can get a shock, or a spark, when you disconnect the battery if the ignition coil or other inductive loads are connected.)

Anything below 50V is considered safe by most legal/regulatory authorities. Above that and it has to be insulated/isolated.

Those joke-toys that shock you are the opposite. They can put-out thousands of volts with no load (or at very-low current) but when attached to your skin the voltage drops.

but 12V through the resistance of your skin/body only results in microamps so you can't even feel it.

But fix the electrodes to thumb tacks and stick it into each wrist and you are a goner.

Fair enough, 100V was a random value.

The problem: I need to measure a small voltage (~2V) in a component. However, this is an inverter which has a minimum DC voltage of 800V and can reach even higher values during switching proposes.

The 8bit controller will be used to measure it. Power supply will be isolated (floating ground and Vcc) and the ground will be connected to 798V. Data will be transferred using earthier optical or wireless (whatever).

I was wondering: is it safe for the device?

thalesmaia: I was wondering: is it safe for the device?

Human safety is important - in general. So as long as humans won't get harmed when all the safety measures are adequately put in place.... then ok. As for the arduino..... it doesn't feel anything.... and relatively inexpensive. And it isn't going to burn if you do everything properly. Just for good measure.... encase the arduino in a suitable plastic case with big red sticker with warning etc.