60V DC dangerous?

Even 6V is dangerous; numerous individuals were killed or maimed working on their cars in the 40's to 70's when most cars had a 6V system. All one needs is to get a ring or other metal object like a wrench across the battery terminals. Orange-hot metal plays no favorites, and if one had recently charged the battery, either fire or an explosion could take place. Then there are a few rare individuals that have extremely low skin resistance - low enough so that sufficent current can go thru the heart to cause serious problems. At 60V, these problems (except maybe hydrogen-related problems) can be magnified.

it all depends on the individual I guess, but I was a telephone engineer for years (-50V DC on the line) and you didn't feel a thing across (even wet) fingers.

Ring signal was a different affair - 90-105V AC - that stung a bit. I remember getting that across chest & left arm while reaching through "open spans" to get to a junction box mounted above the ring-head on a stick. Interesting but not deadly.

Never heard of a tel-eng being "zapped" by line voltage but plenty will attest to the ringing voltage.

Telephone switchboards (PABX) by and large use much lower voltages until you get to some older big ones (kinsman, regent etc.)

poof :o)

On Tue, 04 Jul 2006 07:22:42 GMT, Robert Baer Gave us:

By the ignition coil. 20 to 40 kV (one never knew), and one mean amperage capacity those coils had.

but who

See my other post - 50V and above is considered potentially fatal by the NEC. 48V DC has been used for years by telecom companies likely to avoid dealing with much increased code and safety requirements.

John Larkin skrev:

He also did an elephant:

scary guy,

-Lasse

That's the rule I follow. But if there's 60V DC one got to handle it somehow.

In my book water => no electricity work.

Any risk of coagulation ?

The general rule is to avoid any electricity paths at all times. Only exceptions made are for No wrist straps on HV PS benches... :-]

I never wear anything metallic when doing electronics. Just plain asking for a darwin award.. :)

Maybe it's just too slow ..? I read that many ground protection circuits (useing kirchhoffs law) will protect equipment but not humans due too slow reaction time.

Non-railroad/subway AC shock victims also survive to tell horror stories. In both cases, the ones that don't survive don't get to tell any stories.

I know about ESD risks. And this was mainly about a UPS battery pack capable of delivering 60V 30A. I hope batteries are ESD resistent ;)

The UPS itself may ofcourse be a lot more sensitive.

On 04 Jul 2006 11:51:47 GMT, snipped-for-privacy@spamnuke.ludd.luthdelete.se.invalid Gave us:

If you do not know anything about ESD risks, you should not be working on circuitry.

An HV Supply on a bench is a different story, but for basic analog and digital circuits, there are plenty of fragile, ESD susceptible components on any given assembly. Whether you believe it or not, you can do more damage to an assembly than whatever was wrong with it when you decided to put it on your bench if your workstation is not an ESD safe workstation.

Disagree. Neither our engineering lab nor the mini-lab in my office are ESD stations (my furniture is Ikea) and we don't have problems. If you know that you have an especially tender part, like a gaasfet or some fragile opamp, just handle it properly.

John

On 04 Jul 2006 18:58:53 GMT, snipped-for-privacy@spamnuke.ludd.luthdelete.se.invalid Gave us:

Not from what you wrote, which you conveniently snipped.

I wrote what I wrote based on the CRAP you wrote that you snipped, do try to pull that stupid shit with me.

I'd be willing to bet that even the most basic UPS design has several op amps that are quite sensitive.

The point was that one DOES need to use grounding and ESD smocks and an ESD workstation when on is working on modern electronic equipment.

You were declaring that it was "Darwin Award" territory, which is retarded, and shows a lack of actual experience. If that isn't the case, then the remark was what? A stab in the dark?

On Tue, 04 Jul 2006 12:14:19 -0700, John Larkin Gave us:

Which is what you obviously do not know the correct method for or you would not have said that. Next thing you'll be telling us is that you have a carpeted floor.

Ever heard of "Static Dissipative Packaging"? It is the ONLY safe way to transport an item with ANY ESD susceptibilities from point "A" to point "B" (as in across a room say).

My reading was about 160k by wetting my thumbs and pressing real hard on the probes, but I think body resistance probably drops as soon as any real current flows!

In my office, yes. The big lab is linoleum.

Sorry, disagree. It's easy to learn safe habits without any explicit esd gear or packaging. Most parts are pretty esd-hard these days, and a part can only be damaged if it becomes the discharge path between charged objects, like my body and some other big thing. So simply touch ground once your're seated, before you pick up or put down a part. If you hand someone else a part or an assembly, touch them first. Zero potential makes zero damage. My clenched fist is a mighty fine Faraday cage, better than any silly pink bag.

I think the worst things we have around here are a couple of fabric-covered workbench-type chairs... if you slide your butt off, they can leave you with a hefty charge. These are banned to the kitchen.

Our manufacturing people do follow standard esd rules, straps and all that, because customers expect it and it does potentially affect product quality. But I don't, and I'm not seeing parts fail for unexplained reasons.

ESD supplies, equipment, and training are a big industry, sort of like surge supressors and Monster cables.

John

Watch out for:

1. Skin contact area is not always that small.

1. An electric shock sometimes stimulates sweat glands. I once aplied AC to two points on the same hand, and with steady pressure and steady contact area the current increased with time. Current, especially DC, can cause electrolysis effects that make skin conductivity increase during a shock.

2. Skin resistance has a negative temperature coefficient - which could be a big problem when getting a shock that increases skin temperature. It gets worse when the voltage is high enough to force enough current through a small area to carbonize it.

- Don Klipstein ( snipped-for-privacy@misty.com)

On Tue, 04 Jul 2006 14:54:51 -0700, John Larkin Gave us:

Yet another fallacy.

Pink bags do not qualify in any way shape or form.

On Tue, 04 Jul 2006 14:54:51 -0700, John Larkin Gave us:

You've obviously never seen the photo-micrographs of ESD damage at the input(s) to various chips.

All it takes is the failure of ONE PN junction.

It isn't about big business, it IS about a real issue.

You can generate enough charge to destroy components quite easily by merely lifting your arms above your head if you are isolated from a drain/balance point (ground).

You declaring that it is just a racket, which is essentially what you did, proves that you are not well informed about the issues.