I wonder if that's hot.

I normally use a standard surgical scalpel at the workbench as a general purpose craft knife etc. A couple of days ago I was using it and I had a major slip, letting it fly. My normal reflex is to try and catch things, but I overcame the urge and just managed to get my weight off my bare (it was 40C that day) foot in time to avoid the scalpel. It landed (yep,dart style) right where the foot had been.

comes

fall

Just jinxed myself, wouldn't you know it. I was tinkering with my new IGBTs, Microchip gate driver and PIC (w/associated software for crude SMPS type charge pump). I was applying 12V at 10kHz to a 330uH inductor (w/about 0 ohms of resistance) when "apparently" the HV spikes upset the PIC causing it to lock up. As luck would have it, the gate driver was full on at this point. Suddenly, the IGBT made an "unusual" sound followed by a wisp of smoke. Being an expert at this sort of thing, I opted to not touch it and see if it was hot, yet. Right about then, the bottom right corner sort of opened up like a spring-time flower coming into bloom. What then came into view was some sort of reaction like one might find in the Sun or perhaps within a nuclear reactor. Probably what Ponds and Fleischmann were raving about years ago. I quickly estimated the luminosity of the point light at about 15,000mCd before pulling the battery leads (no wimpy current-limiting foldback supply for me) and retreating from the stench. Maybe I should video tape these experiments?

On Thu, 23 Feb 2006 13:40:16 -0700 in sci.electronics.design, Jim Thompson wrote,

Here is a picture:

of a commercial 12VDC to 120VAC inverter. Labeled "Powermate GSV

200" and given to me by a friend who had no further need of it. Your guess about the circuit design is as good as mine, but I can tell you that the two 2N3772 TO-3 transistors visible in the photo are "hot" in the latter sense. No UL approval sticker.

That reminds me of a guy that worked in the electronics assembly department at one of my previous employers. He and exacto knives didn't really get along.

One day I walked into the room just in time to hear him swearing and see half an exacto knife blade sticking out of one of the knuckles on his left hand.

When I asked him what sort of stupid use of the knife resulted in that situation his reply was something like "It's not always my own stupidity. Exacto knives are out to get me. One day I was sitting here minding my own business and the knife just rolled across the work bench, tipped off the edge pointy end down, and stuck right in my leg and stood there." :-)

had

ROTFLMAO-TWICE!

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

A TV repairman who had a speech impediment came to my house to repair a set that was under warranty when I was about 10 years old. He forgot to discharge the filter cap when he went to check the fusible resistor and got about 150 VDC, which was bad enough, but he was touching the chassis with his other hand. It slammed him into the wall behind him. He picked himself up then exclaimed "That still got juke init!"

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

One of the older techs I worked with was having trouble with a new module on the production test line. I asked if he had checked to make sure that the board was properly stuffed. He said it was, then stuck his finger in it and yelped. He pulled his hand out with the TI logo burnt into the tip of one of his fingers.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

I never pick up a hot iron like that, but I was in someone else's shop one day to pick up some parts and saw something falling of the bench out of the corner of my eye. I caught the iron in the palm of my hand and got some nasty burns. It would have probably been a lot worse, but I grabbed a tube of thick silicone grease and smeared it over the burn to keep it from drying out.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

If you do, it'll never happen again. That's called "applied Murphology"

Meh.. I do that sometimes. The key is a quick touch that only chars the layer of dead skin, and optionally, hydration.

I've noticed that a quick lick (within seconds) sometimes helps out burns. I haven't had a bulging blister in years for this reason. Although I am more careful these days, too. 8-)

Tim

-- Deep Fryer: a very philosophical monk. Website:

I thought you said (in another thread) that at MIT they taught you not to P2P on your hands? :-)

Ed

I remember having heated a large solder joint to remove a heavy wire. My finger slipped, and I had a nice fingerprint in the pool of molten solder.

I learned a lesson about wearing goggles when desoldering. I had heated up a joint and pulled on the wire. When it came loose, a small glob of solder went in my eye. Luckily it was small enough that it didn't fully penetrate, but I had a little metal speck there for a while. It didn't hurt much, but the sizzling sound was scary!

Once, I picked up a metal can power transistor I had just desoldered from a board. I quickly threw it down. My coworker said, "Hot, wasn't it?", and I replied, "No, it just didn't take me long to look at it!".

Some time ago, I emptied a thick layer of cinders from my wood stove into the ash bucket, and after nearly two days, I dumped them into a plastic bag for disposal. I was very surprised when the bag started melting, and I saw flashes of red hot coals that were still hot enough to start burning when air hit them.

My father, as a young man, bought a tube type power supply (which I still have), from a blind radio repair man. He was able to troubleshoot old radios by checking how hot the tubes were: thermally and electrically.

Paul E. Schoen

Some of the descriptions running through here, have had me 'cringing'. As one from 'history', my uncle worked in Radar in WWII. They had a discharger 'hook' that had to be attached to the HT cables, which had a large resistor, that after a couple of minutes would discharge these, to allow work to be done. One day, WAAF's joined the site, and one of them was on cleaning duties, and took it into her head to wax the discharger rod. The next guy to use it, had to be carried out of the site, with his arm stuck in the position it was in when it touched the HT. He did survive... As a guy, who works in electronics, and used to do glass enamelling as a hobby, together with things like gas welding, and reckons that a surgical scalpel, is the best knife for many jobs, my 'get every part of your body out of the way' reflexes, have become honed to perfection (I hope!). :-)

Best Wishes

Or, turn the circuit off for a few minutes. Then hold your finger on the transistor without removing it, and turn the circuit back on. As it's warming up, and you can remove your finger just as it becomes painful but not scalding-third-degree-burn hot.

But yes, the rapid touch, then take a few seconds for the temperature to register in your brain, works pretty well too.

Mark

Heh, I have a piece of solder sitting on top of my monitor right now where I did that. Not as good an impression as I've had other times.

The trick is to use a small piece and time it so it solidifies exactly when you touch it. Too hot and it won't take because it'll still be molten when you pull your finger away, too cold and you'll just be pressing a hot solid, to no use.

Tim

-- Deep Fryer: a very philosophical monk. Website:

My first appreciation for charged capacitors:

I was a kid, about 8 years old, and my dad said, "Son, I'm about to go out and put up that drywall for Ms..Wilson. You keep your hands off that radio! And don't touch anything! I mean nothing! Not the radio, not the vacuum, not the fire alarm, not the refrigerator magnets! You hear me? Nothing! And don't touch that TV. It can shock you even when it's off."

"Shock me even when it's off.... Hmppf. What does he know....the first rule of electronics is that if it's unplugged, it can't do nothing."

As soon as he left the house, I went to garage and got his screwdrivers, carried the family black-and-white TV to my bedroom, got nice and comfortable on floor, and took the cover off. Ooooh...the delight of having that cover off!!.....I'm sure everyone here can appreciate the feeling of having the cover off.

"Doo dee dum dum...look at all those components...look at those red things...look at those orange things....look at that copper wire choking the back of the tube..ooh...look at that...ooh look at that....doo dee dum...I wonder what this big round blue thing is...."

I distinctly remember the metallic, clanging sound that charged metal makes when you discharge it unwittingly, and the sudden uncompromising appreciation for all things other-worldly.

-Le Chaud Lapin-

I always thought the dancing blue stars were SO neat ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

Nice! A digital photo would be nice, at least.

How large was the diameter of the "point light"? Have a geiger counter handy? (j/k)

Keeping the work place quiet is helpfull, too. Often you can hear something suspiciously nasty going on before you can smell it ;)

--
Siol
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