optoisolated power supply

just not a good idea to have anything connected to a living body at the time.

I have some actual warning stickers from the IBM Watson stockroom that say

DANGER LOW VOLTAGE

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

A/D

somewhat

constructed

just not a good idea to have anything connected to a living body at the time.

Industrial low voltage distribution can pack a wallop. Swedish industrial safety film

not a good idea to have anything connected to a living body at the time.

Then the equipotential bonding has not done properly.

The purpose of equipotential bonding is to keep the potential difference between touchable metallic objects below (for people) hazardous levels. However, the absolute potential compared to the surrounding countryside can be very large during a lightning strike.

Used on high current supplies? Drop a screwdriver across a 1000A supply & watch it vaporize.

just not a good idea to have anything connected to a living body at the time.

safety film

Here in the US, cars used to use 6V batteries which were regarded as being very safe due to the low voltage. But there were many incidents of someone wearing a ring getting their hand in exactly the wrong place..losing the ring and finger at minimum. Then there was one case i personally know about where a person with rather low skin resistance "bought" that "its safe" BS and failed to use gloves for protection; the excess current thru the heart killed him; IF that had been AC,he might have had a chance.

My favourite stickers and anodised aluminium plates came in a Ferranti job lot won at auction with the same warning on saying words to the effect "Logic stack covers are essential for cooling do not operate with cover removed". The irony was that this notice would typically be face down on the ground when the mistake was made and the unit fried. The aluminium plates were quite good for heatsinks and small boxes.

This is low voltage as in 240v distribution at high current. I think it is a bit mean not also swapping the pliers for safer insulated ones.

We did have a sparks drop a screwdriver across our works mains panel plunging the entire shed into darkness and no emergency lights. He recovered OK on the application of plenty of hot sweet tea. The screwdriver had a fair chunk missing out of it.

It would take astonishing effort to get killed by 6v DC. Dropping the battery on his head would be the most effective method.

I knew someone who got into trouble with an industrial high current battery charger of nominal 48v output but with lots of ripple and a much higher unloaded voltage and was unable to let go. Co-workers thought he was acting the goat whilst in fact he *was* being electrocuted and unable to let go of the metal clips. The clips were insulated and safety warnings added after that incident.

--
Regards,
Martin Brown

1000A supplies were very common around IBM. Each frame had a couple or three, with unshielded bus bars running all around. No jewelry allowed in the room unless all the covers were on (which was rare). One engineer I worked with specified a 1000A linear supply because he didn't want switching noise. That was some beast (from HP).

[ The university dropped the usenet feed, hence using Google groups ]

Regards, Mikko

We had one in the Vital Industries 'Squeeze Zoom' at WACX-TV.

5V 1000A linear with a 208 three phase input. That was quite a large power supply for a Z80B based computer. :(

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it's just not a good idea to have anything connected to a living body at th= e time.

How low is low? Reminds me that the EC "Low Voltage Directive" covers the range between 50 and 1000 V for alternating current and between 75 and 1500 V for direct current. (So it goes roughly by peak voltage, not rms.)

Can a USB port source 1000 amps?

If you can find a USB port on an old mainframe, try it.

John Larkin a écrit :

Just negotiate it at enumeration...

--
Thanks,
Fred.

safety film

While the panel looked like an ordinary low voltage 230/400 V panel for a larger building, it did not look like something for a detached house.

Based on the material evaporated, the source impedance must have been pretty low, i.e. not in the residential area.

Inserting a wrench between the poles of a fork lift battery, would evaporate a similar amount of metal.

Apart from burning to death by the current flowing through some attached metal objects, I do not understand how you could be killed by

6-24 V, unless both electrodes penetrate your skin.

The EC LVD indeed defines low voltage as 50-1000 Vac and 75-1500 Vdc, the corresponding IEC standard defines the same limit for AC, but for DC 120-1500 Vdc.

In Finland and in some other countries, experimental intermediate 1 kV transmission has been used between the 20 kV medium voltage transmission and 230/400 V distribution in rural areas, using twisted overhead cables certified according to the LV directive.

Twisted 230/400 V or 1 kV overhead cables works weeks with trees hanging on the cable, while the 20 kV overhead open wire conductors snaps each time the tree falls on the line.

A/D

somewhat

constructed

just not a good idea to have anything connected to a living body at the time.

safety film

I once grabbed alligator clips, with wet fingers of opposite hands, and cranked up the DC voltage. My pain limit was about 90 volts. I noted a strange metallic taste for a while afterwards.

I don't think 6 volts DC could cause injury or death, applied externally. 9 volt batteries push more current through a body than a 6 volt battery would, and I never heard of anyone being killed by a 9 volt battery.

AC is more dangerous than DC. 48 volts is generally considered safe "low voltage" AC.

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

You are talking about 99.9% of the crowd. But this guy, like i said had very low skin resistance; a 1.5V penlight cell would shock him. A number of years later, i met someone with very high skin resistance

- hardly felt 120VAC.

Would have troubles at 10A even tho that is beyond the specs.

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You clearly have not seen the warning signs on 48V telecom equipment. = That is DC. They are there for a reason.

?-(