Searching \ for '[EE]: Safety of 12V dc to 110v ac using D cells' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/power/batterys.htm?key=12v
Search entire site for: 'Safety of 12V dc to 110v ac using D cells'.

Exact match. Not showing close matches.
PICList Thread
'[EE]: Safety of 12V dc to 110v ac using D cells'
2005\11\14@122033 by John Waters

picon face
Hi All,

I saw a kind of 12v dc to 110v ac inverters selling in electrical stores
that allow people to drive their laptops in a car. I want to use it to drive
a small device that uses 110v and consumes power less than 3 Watts. But
instead of using the car battery, I want to use 8 pieces of D cells as the
dc source. The reason is, the 110v ac generated this way would be very safe
even when someone accidentally touches it? It is hard to imagine 8 D cells
could kill someone, right? Could anybody give some comments to my argument?

Thanks in advance!

John


2005\11\14@123349 by Robert Young

picon face
> dc source. The reason is, the 110v ac generated this way
> would be very safe
> even when someone accidentally touches it? It is hard to
> imagine 8 D cells
> could kill someone, right? Could anybody give some comments
> to my argument?

It ain't the volts, its the amps...

Doesn't take very much AC current to stop a heart or throw it off rhythm
if applied correctly.

Rob

2005\11\14@125053 by Wouter van Ooijen

face picon face
> The reason is, the 110v ac generated this way
> would be very safe
> even when someone accidentally touches it?

Probably, but not for the reason you think. Touching one pole is mostly
harmless if you are not connected also to the other pole, so an isolated
110V is much more safe than a ground-referenced 110v.

> It is hard to imagine 8 D cells
> could kill someone, right?

No problem at all. With the right circuitry and connected correctly I'm
sure 8 D cells can kill.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\11\14@125606 by Mike Hord

picon face
> I saw a kind of 12v dc to 110v ac inverters selling in electrical stores
> that allow people to drive their laptops in a car. I want to use it to drive
> a small device that uses 110v and consumes power less than 3 Watts. But
> instead of using the car battery, I want to use 8 pieces of D cells as the
> dc source. The reason is, the 110v ac generated this way would be very safe
> even when someone accidentally touches it? It is hard to imagine 8 D cells
> could kill someone, right? Could anybody give some comments to my argument?

Batteries absolutely, positively can kill someone.

I'll trot out the old story:  I once saw someone connect the end
terminals of 60-odd 9V batteries through the palms of his hands
(not intentionally, of course).  The entry and exit points were third
degree burns.

Of course, that was 360+ alkaline cells, instead of 8, but the key
problem is still there:  with the output from that inverter, or the
wall socket, or your car's cigarette lighter, the current is limited
somehow.  A fuse, a polyfuse, a breaker, whatever, but limited.
Batteries have a much looser limit, namely the internal resistance
of the cell.  So while your wall breaker will trip at 10 or 20 amps,
a battery will happily carry on sourcing current way past that
(up to hundreds of amps, for some types), if only for a brief time.

In other words, the current limitation on this system won't come
from the fact that it's running on D-cells.  It'll come in the form
of fusing or a circuit breaker on the output (although the input
is no doubt fused as well).  In other words, the output from that
inverter is neither safer nor more dangerous than the wall outlets
in your house.

Mike H.

2005\11\14@135414 by Bob Axtell

face picon face
John Waters wrote:

> Hi All,
>
> I saw a kind of 12v dc to 110v ac inverters selling in electrical
> stores that allow people to drive their laptops in a car. I want to
> use it to drive a small device that uses 110v and consumes power less
> than 3 Watts. But instead of using the car battery, I want to use 8
> pieces of D cells as the dc source. The reason is, the 110v ac
> generated this way would be very safe even when someone accidentally
> touches it? It is hard to imagine 8 D cells could kill someone, right?
> Could anybody give some comments to my argument?
>
> Thanks in advance!
>
> John
>
>
The very first item I designed as a young engineer was a custom
detonator for oil exploration (sesmic) explosions in the Guatemalan
jungle. It converted 6 D cells (9V) to 110V DC in order to set off
downhole explosions using  a transistor-driven oscillator, a
transformer, an SCR , a heavy cap, and an early optoisolator. While
blasting caps are "guaranteed"  to explode at 6V, we wired two in
parallel and applied 110 VDC because we'd had failures at 12V (normal
blasting voltages) due to heavy moisture.

Even though we used a charge bleeder (a heavy resistor to bleed off the
charge) , the 110VDC was easily capable of killing anyone touching it.

--Bob


--
Note: To protect our network,
attachments must be sent to
spam_OUTattachTakeThisOuTspamengineer.cotse.net .
1-520-777-7606 USA/Canada
http://beam.to/azengineer

2005\11\14@174525 by Jinx

face picon face
> It ain't the volts, its the amps...

It's really the right combination / right circumstances. Even though
a single D-cell can deliver a few amps, it hasn't enough potential

http://en.wikipedia.org/wiki/Electric_shock

http://www.stanselectric.com/shock.html

You have people hit by lightning (sometimes several times, poor
buggers) who avoid death because the path through the body
missed the heart. Enough to blow them out of their shoes though

But grab a live appliance with the wrong hand .......

The situation with an inverter powered by 8 batteries is similar
to that of an isolating transformer. You probably wouldn't even
feel one touching one output terminal (assuming the whole thing
really is floating and there's no ground reference) but one in each
hand is not to be recommended

2005\11\14@182440 by Robert Young

picon face

> -----Original Message-----
> From: .....piclist-bouncesKILLspamspam@spam@mit.edu
> [piclist-bouncesspamKILLspammit.edu] On Behalf Of Jinx
> Sent: Monday, November 14, 2005 4:46 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE]: Safety of 12V dc to 110v ac using D cells
>
>
> > It ain't the volts, its the amps...
>
> It's really the right combination / right circumstances. Even
> though a single D-cell can deliver a few amps, it hasn't
> enough potential

Yes, I was being a bit facetious.  

See if you can get your hands on IEC 60479-1 which relates to the
effects of current passing through the human body.  I only have excepted
portions of it.  An official copy is around $150 but you might find
somebody with a copy you can borrow, read and return.  A good library
might have one, especially a university library.

IEC 61140 has information relating to rules of protection.  Again, I
don't have a full copy handy, just excerpts.

Rob

More... (looser matching)
- Last day of these posts
- In 2005 , 2006 only
- Today
- New search...