SON OF A...

[Ben]

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@crossrulz wrote:

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@JW-L3CE wrote:

All of these horror stories make me feel weak for getting shocked by a 220V power rail.

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Yeah, I feel the same about my 1.5kV straight from a large capacitor.

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That was rumored to be a rookie trick when I was in the Navy. Motor and generator winding required high voltage checks of the insulation usinga a "Megger" which was a meter with a built-in hand operated generator to gen the high voltage. The story went the megger would be used to charge a cap that would then be tossed to a rookie.

We did not have access to a megger so I never saw the game myself.

Any of you EEs out there heard the same story?

Being bit by DC and AC are different experiences with one shaking you violently and the other blasting you with a single shot.

neither are fun.

Ben

[GregFreeman]

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@Ben wrote:

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Being bit by DC and AC are different experiences with one shaking you violently and the other blasting you with a single shot.

neither are fun.

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One of my customers told me a story of a guy walking out of one of their portable testing trailers with his hand on a railing. I forget what he touched with his other hand but it completed a 220 V circuit and knocked him all the way off the steps.

[RobCole]

In school we used to charge the big caps then go to the locker area and touch the frame and door with the contacts. Spot welds the door shut. I never saw anyone touch one.

My second job out of school (the first is barely worth mentioning), we had amplifiers for our vibration tables that used 600V, 100A service. My co-worker was trying to diagnose a loss of power on one amp and had the plug unbolted. Despite the very thick cabling it managed to fall down and short to the frame. Another worker and I were outside the door and heard the bang and saw our shadows clearly on the far wall - the entire length of a warehouse. We rushed in to find the guy standing there blinking. He couldn't hear us when we talked to him and couldn't see us. Luckily it was only temporary. He made a full recovery.

[Ray.R]

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@Ben wrote:

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Any of you EEs out there heard the same story?

Being bit by DC and AC are different experiences with one shaking you violently and the other blasting you with a single shot.

neither are fun.

Ben

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I'm afraid I have to raise my hand.

Worked on power supplies...  One test was using a "Dielectric Strength Tester", which some people compared to a megger..

This baby was able to generate 2500V at 0.25A.

I needed to test a power supply which was inside a metal enclosure.  The enclosure was on hinges with a side bar to hold up the top cover.

The bloody side bar kept dislodging and the cover would not stay up..  So I held the cover up with the left hand and went in with the probe already set to 2500V with the right hand.

To this day, I do not know what touched what.  All I remembered was being 6 to 10 feet away from the enclosure feeling as though (d'Oh) something hit me.  I was numb, completely disoriented and everything was black.. Not dark, completely black.  Suddently things started clearing up.  I realized where I was but didn't understand why the lights were out until a small dot of light appeared and slowly it grew until my vision came back.  The dot of light was similar to a very old B&W tv set when you turned it off, but in reverse.

I was rather embarassed by the experience and kept quiet about it.  I made sure the over was WELL secured before attempting the test again.

[SteveChandler]

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@Ben wrote:

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@crossrulz wrote:

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@JW-L3CE wrote:

All of these horror stories make me feel weak for getting shocked by a 220V power rail.

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Yeah, I feel the same about my 1.5kV straight from a large capacitor.

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That was rumored to be a rookie trick when I was in the Navy. Motor and generator winding required high voltage checks of the insulation usinga a "Megger" which was a meter with a built-in hand operated generator to gen the high voltage. The story went the megger would be used to charge a cap that would then be tossed to a rookie.

We did not have access to a megger so I never saw the game myself.

Any of you EEs out there heard the same story?

Being bit by DC and AC are different experiences with one shaking you violently and the other blasting you with a single shot.

neither are fun.

Ben

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I can tell you what does work. Inside of one of those disposable cameras with an electronic flash is a tiny little nasty circuit to generate thousands of volts from a small battery. Play "here catch" with someone that you know does not have a pace-maker while trying not to get shocked yourself. Those things really hurt!

On second thought don't do it. Just pretend you did and laugh about it anyway.

The reason I know this is from trying to modify one of those little monsters in the camera to flash, charge, flash, charge, etc. I was going to attach it to a big helium balloon and let it go over by the Air Force base late at night. I gave up after several "SON OF A!!!'s". I can admit this for at least two reasons. First I never was successful. Second, even if I was successful, I was a young stupid kid and the statute of limitations has expired.

[Ray.R]

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@JackDunaway wrote:

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for(imstuck) wrote:

Maybe we should turn this into a thread of "engineering mistakes that have made one say sonofaaaaa...."

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One of my first engineering catastropic failures was while installing some big-a car stereo system into my old beater (yes, this is embarrassing now, but at age 17, it just felt like the right thing to do at the time).

I was routing 4/0 cable and some ungodly-sized fuse (150-200A?). The fuse holder was mounted on a lead about 8-10" from the positive terminal clamp. After wrenching this short lead onto the +terminal, I *very carefully* laid down the lead, careful to miss anything grounded in the engine compartment. And not just *very carefully*, we're talking painstakingingly carefully laid this lead down. Moving at about an inch every two seconds, I missed every single grounded component on the car except for the negative terminal itself.

It wasn't until years later - during my electrical engineering training when I was introduced to Drawn-Arc Stud Welding - that I saw a spark-fest as horrifying yet transmogrifyingly fixating. When you're in the 600-cold-cranking-amps-and-4/0-cable domain, it's surprising what element in the system becomes the fusable link 

Spoiler

It was the negative terminal - blew a chunk of the sucker to smithereens

  

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This takes me back to my fooling & young years...

The 2nd car I owned was quite the experience.  Learned lots of auto mechanics with it.  I should have kept the first one.

Early after buying it, the battery was dead.  So I got a new one and replaced it.

And proceeded to fully charge the new battery.

Then I connected the terminals which were secured in place using a ratchet wrench.  And yes, I was careful when doing this.

My brother distracted me (for a reason that I can no longer remember).

Then a hugely loud BOOOOOOMMM!!!

The wrench must have shorted to the other terminal.  After shaking off the ringing in my ears, I noticed that the battery was gone.  I mean GONE!  The only thing remaining was the bottom plate.  Fortunately, I wore glasses at the time.  I was fully covered in battery acid, which I washed off right away. 

I was lucky. No injury and the ringing in the ears went away.  I am now the more careful when dealing with car batteries.  Oh... and I had to buy yet another new battery.  That part was not fun.  And no.. I did not attempt to return the battery on warranty.  😛

[Ben]

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@Steve Chandler wrote:

... First I never was successful. Second, even if I was successful, I was a young stupid kid and the statute of limitations has expired.

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I believe the timer for the statute of limitation starts when the crime is discovered not commited.

I will not start any timers for myself but I will quote David

"Forgive me for the sins of my youth."

Which in my case requires a lot of forgiving.

Ben

[ChrissyC]

Not really much to do with work, but funny to look back on:

During the Summer break from Uni a few years ago, three friends and I were doing some temp. manual labour at our local wildlife park. They've got a small diesel train and our job was to re-level the tracks all the way around the park - cue 6ft.crowbars, shovels, hardcore and crippled hands!

Anyway, the tracks run right next to the animal enclosures and as I was levering up one of the tracks, I must have slipped the crowbar through the enclosure fencing and touched the electric fence beyond! Felt like someone had smacked me in the chest with one of the shovels! God knows what sort of animal they were keeping in there but i'm sure the shock would have been enough for the T-rex pen at Jurrasic Park! 

[SteveChandler]

Fortunately I never commited any crimes. Ever!

Spoiler

[JW-JnJ]

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Ben wrote:

Being bit by DC and AC are different experiences with one shaking you violently and the other blasting you with a single shot.

neither are fun.

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My brush with electrons was in a REALLY finicky bottom loading heater when I was a student ceramic test tech. That baby could get ceramics blindingly hot but was prone to breaking every 2 weeks. To this day, I want to give the designer a piece of my mind. Maybe it's standard practice, but I think designing an uncovered, unprotected 220V metal bar in a box is a bad idea. Luckily the muscle spasm pulled my hand away.

Thats right kids, always check that you unplugged it twice.