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Stupidest Mistake

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Alex M

Thu Apr 05 2012, 06:15PM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

Apart from getting the odd shock here is one;

I had just bought some alligator clips and made some jumper wires and this was my first time using them in a circuit.

But the coloured insulated sleeves that came with them were in an odd quantity, there were 3 black and 3 red so one of the jumpers had a red and black coloured clip on the ends.

I had just connected everything up and powered the circuit on when instantly the 5 amp fuse blew. Thinking that I had connected something wrong I double checked and replaced the fuse. Same thing happened again so I put a 13 amp fuse in there as I though it just needed more current. Turn power switch on and "pop" fuse blew again.

Upon closer inspection I had connected the red end of that one jumper wire to the supply rails and the black end directly to ground! so every-time I powered it on I was just shorting the lead acid battery.

Not really a life threatening mistake but still makes me lol thinking about it.

Forty

Thu Apr 05 2012, 06:54PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

I installed a digital panel meter into one of my demo coilguns so that I didn't need an external meter all the time. The box had a 12v smps in it for driving the zvs charger, and off of that I had a 6v regulator for powering the panel meter and, through a resistor and switch, the SCR gate. I charged it up and it didn't fire when I pressed the button. The gate wasn't receiving enough juice. A safety bleeder resistor wasn't installed yet so I had to carefully open the box up and connect the 12v to the switch so it would fire. It worked, but I fried the panel meter that I forgot was connected to the same supply as the gate switch. Barely had the meter out of the box for 2 hours before it was dead.

Just yesterday, I was building several dielectric barrier discharge prototypes to play around with. First two worked pretty well, just slapped together from plastic, glass, and aluminum tape. Occasional arc over on the first light simply required trimming down the foil tape. I thought I'd get fancy for the third and used two front surface mirrors from polaroid cameras to make the conductor and insulator layers. Carefully taped off the mirrors and went around the edges and scraped off the mirror coating so that the conductor didn't extend all the way to the edge. First light arced over again and it was here that I learned that hv arcs erase mirrors much like they do to cd's. At least I learned an effective way of etching conductive coatings off of glass.

Alex M

Thu Apr 05 2012, 07:46PM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

Forty wrote ...

hv arcs erase mirrors much like they do to cd's. At least I learned an effective way of etching conductive coatings off of glass.

Should try it with a large capacitor bank. One second the metallised surface on the disc is there, next second it vanishes!

coillah

Thu Apr 05 2012, 09:05PM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

Almost smoked a 24v transformer because I hooked mains to the secondary.

Also, burnt out a $3 led driver chip the other night because I was sloppily connecting high voltage to the logic side... durp

Goodchild

Thu Apr 05 2012, 09:06PM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

I inadvertently touched the primary of a running QCW with 120A at 4Ak pulsing through it, it hurt....

I however touched the QCW sparks on purpose!

That was fun!

Tetris

Fri Apr 06 2012, 01:56AM

Registered Member #4016 Joined: Thu Jul 21 2011, 01:52AM
Location: Gainesville, FL
Posts: 660

AndrewM wrote ...

When I was a senior in high school I used to charge up camera flash capacitors and then toss them to people during class. They would invariably reach out and catch them.

... heeeheee. I may be old enough to realize it was stupid, now, but its also still funny.

Hehehehe. Oh poor Pete Pioli... I can still remember him going redfaced in Calculus trying not to shout. Haha.

I can picture that. *bweeeeee....* HERE. CATCH! I've gotten kids to touch modified ones.

Jrz126

Sat Apr 07 2012, 02:01PM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

about 10 years ago, I was helping a friend remove an engine from an old car he was scrapping. We didnt have a engine hoist, so we decided to cut the front of the car and pull it out. I was running the oxygen acetylene torches, while cutting through the bumper i saw a cylinder shape. i wondered what it was, but figured whatever, it'll cut. I put a pinhole in it and it blew up in my face. Turns out it was a gas shock to absorb impacts.

3rd degree on my nose and ear, 2nd degree burns on my face and neck. Spent the next month on the couch recovering. I only have a tiny scar on my ear.

Dri0m

Mon May 07 2012, 02:42PM

Registered Member #4497 Joined: Thu Apr 19 2012, 12:53PM
Location: Behind you
Posts: 62

once i accidentally touched output from 4kVAC homemade fryback, and the second (insulated) wire was in my hand... bzzzzzzZZZZZZ.... i got a ****ing strong electric shock that almost killed me

Tetris

Mon May 07 2012, 03:42PM

Registered Member #4016 Joined: Thu Jul 21 2011, 01:52AM
Location: Gainesville, FL
Posts: 660

Dri0m wrote ...

once i accidentally touched output from 4kVAC homemade fryback, and the second (insulated) wire was in my hand... bzzzzzzZZZZZZ.... i got a ****ing strong electric shock that almost killed me

Flybacks rarely put out a deadly current. They are usually 2-5mA, but big ones can get up to 10mA. 10mA, for some people hurts extremely badly, but it is no where a deadly current. I've touched 10mA many times, I find it rather pleasant, actually, but I am yet to accidentally touch a flyback output. I nearly accidentally did though this past weekend-- I forgot I had it on, and was leaning too close to the circuit, when I noticed that it was making a sound. Just be careful, Dri0m, if that was a MOT, you almost certainly wouldn't be typing that electronics fail now. :P

Note: Be sure to secure your toploads on your secondary on a Tesla Coil. Otherwise you will knock it over with a grounding stick, it will nearly fall on you, and in an evasive action, you will jump backwards, hitting your tailbone right on the sharp edge of the open car door. Not strictly speaking an electrical fail, but I was told you didn't need to secure the topload, and I found that it is better to do so, to avoid a non-shock related injury.

Forty

Mon May 07 2012, 05:40PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

read more carefully.
He said it was a homemade transformer, so it could have been outputting much more current than a typical flyback.

Glad you're alright Dri0m

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