Your stupidest mistakes

[rs20]

my most stupidest mistake is something i did quite a few times:
I did not check the voltage of a powersupply despite the fact that i knew it was unrealible.
Result was: smoking stuff on boards
At least my coworker roasted a few boards that way too...

Sounds? to me like the stupidest thing here was not discarding/fixing the supply after incident #1...

[Matthew98]

I guess when i was a kid... I salvaged some 5V motors from rc cars and made alternatve cars with them (like attaching a blade to a motor and let the car blow away.... yeah.. )) ) anyway one day, when 9V battery went flat i was like : Man, how am i gonna make the motor spin faster ? and than i saw mains plug in front of me..... It blew me away with sparks all over the place ))) from than im very careful with mains...

[Cubdriver]

Hard to say what my stupidest mistake might have been, but a memorable mistake was when I set my house on fire.

Nearly 60 years ago when I was a kid experimenter, I built a Jacob's ladder using a neon transformer in my basement workshop. It worked quite well. Then, leaving it on, I went upstairs to get a snack. While eating I smelled smoke. Ran downstairs and found my workshop on fire. The arc had set some nearby paper on fire. I managed to get it put out before the fire department arrived.

Wikipedia has the following in their article on Jacob's ladders:

Traveling-arc devices are dangerous. The sparks can burn through thin paper and plastic and start fires, and contact with the exposed high-voltage conductors can be lethal.[citation needed]

Citation needed? 

I didn't stop to think about the possible fire danger although I was well aware of the high voltage danger. But if someone had told me at the time that there was a fire danger I surely wouldn't have said "I don't believe it. What is your source?".

Not my mistake, but a friend's brief shining moment of sheer idiocy.  Back in my late teens/early 20s I had some friends over (not a particularly technical bunch, but all in college, mind you, so expected to be at least somewhat smarter than a sack of hammers) and was showing them a Jacob's Ladder that I'd made up with some coat hanger wire and a 10 kV oil burner ignition transformer.  The ladder was about 14" tall and opened to perhaps 3" wide at the top.  The nice fat blue spark was starting at the bottom and merrily climbing before splaying out at the top and extinguishing, as Jacob's Ladders do.

I had just shown them how the spark would ignite a piece of paper held in its path.  A mere moment after this demonstration, one of them says "If I put my hand in there, will I get a shock?", and before I can process and react proceeds to stick his hand between the wires and in the path of the rapidly ascending spark.  Needless to say, he removed his hand very quickly and then spent some time attempting to massage some feeling back into it.  All I could say was "I dunno, George - it's a 3 inch long spark, and you just watched it set a piece of paper on fire.  What do you think will happen?!?"

 

Going on 30 years later I still occasionally bust his balls about that little stunt.   

-Pat

[obiwanjacobi]

Fresh out of school, first job. We had renovated an elctro-mechanical cigarette vending machine to support a new dutch 5-guilder coin (before the euro) and the price of a pack of cigarettes had rissen above the amount the electro-mechanical step-counter could count.

So we ripped out the counter and some other relais we no longer needed, outfitted it with an electronic-coin reader (one of the specialties of the company I worked at) and added a 2x16 LCD and an 68HC11 micro - this was 1992.

After we managed the reverse voltages and spikes that we flying around in the cabinet, it all worked fine. I had almost filled the 4k flash with the program to control it all.

The customer was very content and went of to put his vending machines in the field. Of course there were some small bugs still in there, so a new version of the software had to be made. We tested it on the vending machine we still had in our shop and sent him the new chips (he would return the old chips).

A couple of days later he called and said that some-one had emptied out a couple of his machines. Turned out that my recent changes in the software at opened up a 'security hole' that allowed you to make the vending machine to repeatedly output cigarettes while only paying once by locking the mechanical select buttons.

That was the worst I have ever felt, I think. I felt so responsible. Luckily I found the bug quickly and we could send out the fix the same day.

It tought me a valuable lesson about software/hardware testing.

[SingedFingers]

Today's fuck up. Hmm not 0.1" pitch!



Nope didn't read the datasheet before I bought 20 of these ... at least I've got some SMD protoboards now!

[fuzzoli]

20 years or so ago, we were working on code which screen scraped mainframe 3270 screens.  I had several terminal windows open when the conversation went something like this:

Coworker:  Why did you just shutdown the Production window?
Me:  No, I didn't.
Coworker:  Yes, you did.  Look at the server name.
Me:   

AFTER fixing the problem, I went into my boss's office and explained what I just did.   

Fortunately she understood, but made me write and send the email to our business partners explaining what happened.

Ever since then, I have a code I live by:

   Anything Dev (terminal windows, etc.) is Green.
   Anything Test is Yellow
   Anything Stage/PreProd is Orange(ish)
and
   Anything Red means "Think VERY carefully before pressing Enter!"   

I have never taken down Production since.

[nidlaX]

My most recent moment was spending 10+ hours on a Fluke 199C probing test points, measuring components, looking for signs of physical damage, and poring over schematics when the problem was that I forgot to increase the current limit on my power supply, thereby preventing a complete power on.

It's helpful to make sure the instrument is actually broken before attempting a repair.

[eugenenine]

20 years or so ago, we were working on code which screen scraped mainframe 3270 screens.  I had several terminal windows open when the conversation went something like this:

Coworker:  Why did you just shutdown the Production window?
Me:  No, I didn't.
Coworker:  Yes, you did.  Look at the server name.
Me:   

AFTER fixing the problem, I went into my boss's office and explained what I just did.   

Fortunately she understood, but made me write and send the email to our business partners explaining what happened.

Ever since then, I have a code I live by:

   Anything Dev (terminal windows, etc.) is Green.
   Anything Test is Yellow
   Anything Stage/PreProd is Orange(ish)
and
   Anything Red means "Think VERY carefully before pressing Enter!"   

I have never taken down Production since.

I had a hung backup server back in the days of mechanical power switches.  I had to call my cow-orker from the server room and ask him to have everyone close outlook because I pushed the button on the exchange server by accident.  I realized it as I was pressing it so as long as I held it in the exchange server had power but it had already clicked so as soon as I released it it was going off.

[rs20]

20 years or so ago, we were working on code which screen scraped mainframe 3270 screens.  I had several terminal windows open when the conversation went something like this:

Coworker:  Why did you just shutdown the Production window?
Me:  No, I didn't.
Coworker:  Yes, you did.  Look at the server name.
Me:   

AFTER fixing the problem, I went into my boss's office and explained what I just did.   

Fortunately she understood, but made me write and send the email to our business partners explaining what happened.

Ever since then, I have a code I live by:

   Anything Dev (terminal windows, etc.) is Green.
   Anything Test is Yellow
   Anything Stage/PreProd is Orange(ish)
and
   Anything Red means "Think VERY carefully before pressing Enter!"   

I have never taken down Production since.

Wait, you have a production service running in a terminal window, and just closing that terminal window kills the service? Or did I misread?

[fuzzoli]

Wait, you have a production service running in a terminal window, and just closing that terminal window kills the service? Or did I misread?

Nah, closing the window wouldn't have done any harm.  Back in the day before web services and APIs, the only way to get data off the mainframes was to scrape data from a terminal.  There was software which emulated 3270/5250 screens, let you wait for certain characters at certain positions, and then "scrape" off the data you needed.  One of the tools let you watch the window as the app traversed the screens.  Part of the tool also let you reset and restart the windows (for when things got confused).  That was my downfall.  I thought I was restarting the development system, but since the development team also did production support back then, I had prod windows open too.  Oops! 

[Tom45]

I had a hung backup server back in the days of mechanical power switches.  I had to call my cow-orker from the server room and ask him to have everyone close outlook because I pushed the button on the exchange server by accident.  I realized it as I was pressing it so as long as I held it in the exchange server had power but it had already clicked so as soon as I released it it was going off.

Holding that button sounds like the Dutch boy with his finger in the dyke.

[Sjoertdb]

One of mine:
Not supporting a supply from the programmer simultaneously with the main supply 

[steaky1212]

I had a hung backup server back in the days of mechanical power switches.  I had to call my co-worker from the server room and ask him to have everyone close outlook because I pushed the button on the exchange server by accident.  I realized it as I was pressing it so as long as I held it in the exchange server had power but it had already clicked so as soon as I released it it was going off.

I used to do this to my brother when I wanted to go on the computer. If you were quick you could release the button and press it again without the computer going off.

[JenniferG]

My stupidist mistake was when I was about 11 years old and decided to cut a lamp cord with diagonal cutters while still plugged in.  Made a few burn marks on my hand, gigantic arc and scared the heck out of me. I HAVE no clue to this day why I did such a thing!

[Zbig]

My stupidist mistake was when I was about 11 years old and decided to cut a lamp cord with diagonal cutters while still plugged in.  Made a few burn marks on my hand, gigantic arc and scared the heck out of me. I HAVE no clue to this day why I did such a thing!

I once ordered some dubious quality RC Li-Po packs, 3S 1800 mAh or so. Some of them arrived pre-puffed already so I decided to scrap them, salvaging the heavy-gauge wires and plugs first. I stumbled upon my dad so I asked him to grab his heavy duty shears and cut the wires. I only managed to say something like "but carefully; one by one, don't short them as they're capable of delivering quite some cur... BLAST!!!" He looked surprised even thouh he's not really that easily impressionable.

[SeanB]

When I was very young, I wanted to light up a flourescent lamp starter like a neon lamp. So, take one old starter, and look around at the plugs, and decide the 5A socket outlet adaptor will fit the prongs nicely, so put it in there, and then turn on the power.

Instant conversion of the lamp to nothing, only the base left there on the floor where it landed, and the dog did a fair imitation of a bullet and vanished to far away.  Go to the laundry, where Dad had installed the new fangled at the time ( it came from Australia, complete with 2 Australian socket outlets and 2 rewireable plugs for them) RDC and breakers, which he had fed from the fuse box ( yes, old houses here still have fuses in some, only thing that has to happen with a sale or any electrical work is RCD installation, which often results in a rewire because DCC wire really is leaky, some cheapskates only replace the live with PVC as well and leave the DCC neutral as well, which is crap) using a good length of Pyrotenax cable.  Reset the breakers, check the lights still worked, checked pants for more skid marks and ( with the power switched off) swiped most of the copper stain away from the 5A adaptor.

Never found anything more than the bakelite base, with the melted pins, and half a capacitor in the pins and no capsule, or it's wire leads. I must have been around 7 at the time, as I was at primary school down the road. no driving there, we all walked every day, wet days with a raincoat. Fun days playing in the bush and at the local river.

[tautech]

Personally I have a lot to that my father for, he was a farmer but in his youth had a passion for Shortwave, built his own valve receivers and listened to shortwave stations from all over the world, this was late 40's and early 50's. Farmers were a resourceful lot having to fix and maintain all manner of their own plant due to their remoteness from service and repair facilities. He had a small but adequate kit of gear and all manner old old stuff in the sheds which was gladly offered to the young enquiring minds to keep us occupied rather than get under his feet.
After a few stern words about not losing any of his tools and an insistence to return them to where we found them we were off into the big boys world of fixing stuff. 

IIRC my first patient was a Villiers MK 10 engine that was quickly spirited home to the basement where I could tackle with gusto. Some infrequent supervision followed with instruction that it MUST have spark, fuel and compression in order to run. So of course a cocky younster must tackle the most difficult first....spark.
Off came the covers and cowlings to expose the flywheel, under which were the ignition points, that of course must be mandatorily cleaned. 
On the Villiers flywheel there was a cover plate and when removed you could look through between the 3 spokes of the flywheel to see the ignition points housing which was covered by another cover plate and once removed you can see, clean and adjust the points. 
Not knowing how to proceed I marvelled at the workings in detail, rotating the flywheel too and fro by hand while watching the points open and close and lining up with the timing marks and the piston reaching top dead center. 

ZAP   

Even at such a young age (under 10) I instantly had great respect for electricity and steps that heeded to be taken to keep one safe. That Villiers never bit me again and for a short while later in my teens I worked on all manner of small motors for a living.

Back to the Villiers, Dad showed me how to remove the flywheel, these old Villiers where great in this respect with a captured flywheel nut that when undone pulled the flywheel from the crankshaft taper. 
Cleaned the points and was rewarded with a nice spark with a yank on the starter cord.
Then came the carburetor which of course must be duly removed and dismantled and inspected in great detail. 

Finally it was all ready to be reassembled and a start attempted......I couldn't wait. 
Spark, check.
Petrol, check.

First pull.....nothing, OK    Select full choke. 
Second pull.....Yiha, flick choke off..........holy hell, off at full revs....I mean FULL revs. 
Shite, I wish I'd mounted this motor on something it was dancing all around the concrete floor of the basement. 
How many things rush through your mind when things go bad still amazes me but quickly I realised in my haste to get it running I'd left the speed governor linkage loose. 
Young as I was, I just had to man up and grab the thing and press the stop button....
 
The racket had stopped and I was safe now.   

I still remember how hard my heart was beating 50 yrs later. 

Hell look at all those marks on the basement concrete floor  .....what can I do to tidy those  ah, broom a little dirt over them.    Yep all kids will try and hide their mistakes. 
Just got things sort of tidy and mum appeared wondering what all the commotion was.  Who me? I was a little angel. 

Problem identified and fixed....ten minutes later after double and treble checking the governor linkage I had it running like a Swiss watch.     

What will be the next victim.....me, that's another story. 

[Cubdriver]

SeanB's reminds me of one from high school.  I came across some geared synchronous motors in the supply crib, and found that if I held the output shaft tightly enough, I could turn it and spin the motor.  I also had on hand a few NE-2 lamps.  I got curious, and connected one of the neon lamps to the motor leads and noted that the motor could act as a generator, and because of the reduction gearing twisting the output shaft would spin it fast enough to put out sufficient voltage to light the neon lamp.  I wandered about the shop showing friends for a while, and then got curious as to exactly how fast 4 RPM actually was (this was the speed noted on the motor's dataplate).  Without further ado, I stuck the stripped lead ends into a 120V mains receptacle.  (Note that I never mentioned a series resistor for the neon, nor have I said anything about disconnecting it from the motor leads.  I was aware that neon lamps needed dropping resistors, but not really fully conscious of the reason why, I suppose.)

As the leads went into the socket, my failure to disconnect the neon lamp was almost instantaneously rectified as it flashed very briefly and then with a pop turned into a rapidly expanding ball of tiny crumbs of glass shrapnel and, I suppose, vaporized metal from the electrodes.  Fortunately I wore glasses, as my nose was about a foot away as I leaned over the bench to plug it in.  They protected my eyes, and I had only the slightest flash burn on the back of my thumbs, which of course were holding the ends of the motor leads an inch or so from the space that a split second earlier been occupied by a lamp.  Luckily for me, the teacher did not notice the incident, so I avoided getting in hot water for it.  It definitely emphasized the low resistance presented by ionized gas, and I have not since connected a glow lamp without an appropriate series resistor.

We later had great fun zapping each other with the motor, and when the basic electronics teacher (we were seniors at the time; he taught the freshmen and sophomores) found out what we were up to actually got his 2nd year students to line up and form a series circuit by touching one another, and he then zapped the whole lot of them in one shot.  He was pretty cool, and was hands down the best teacher I ever had.

-Pat

[Cubdriver]

My stupidist mistake was when I was about 11 years old and decided to cut a lamp cord with diagonal cutters while still plugged in.  Made a few burn marks on my hand, gigantic arc and scared the heck out of me. I HAVE no clue to this day why I did such a thing!

You wanted wire strippers, like RIGHT NOW?   

I made one of those, too.  On the blade of what already was a wire stripper.   



Lessons learned - sometimes there are multiple power sources feeding a switchbox, especially when it contains (4) 3 way switches and controls lights in the basement AND the garage (and was wired 50 odd years ago by your father and his drinking buddies  ).  It is prudent to ensure that ALL of them are turned off before doing electrical work at 1:30 AM.    

Extra credit lesson - doing electrical work at 0130 when exhausted is not a good idea, as 'prudent' sometimes falls by the wayside.   

Also worth noting - making cutters into strippers in this fashion will also shut off the power source that was missed.  It will also, at least temporarily, cause the exhaustion to go away.   

-Pat

[grumpydoc]

......
Coworker:  Why did you just shutdown the Production window?
......

BTDT

In my case I was the victim as well as the perpetrator - I was on holiday and had logged into the home email server via SSH and VNC. Having finished the admin work I wanted to do I went to shut down my laptop, only to realise I was still looking at the remote VNC session full-screen so when I chose System->Power Off, it was the server, not the laptop. Oops.

Managed to get the neighbour who was babysitting the cats to restart things.

My most expensive mistake recently was actually woodworking at which I'm hopeless anyway but fitting a new worktop and sink I carefully measured (repeatedly, in case of error) the length I needed and then proceeded to cut a £170 ($215) piece of wood 10cm too short.

Because of the orientation of the tape I was looking at the markings upside down and subtracted from the nearest 10cm mark rather than adding. 

On the subject of tapes and rules in the UK it's pretty common to get them marked in imperial and metric. They are invariably marked on both sides such that all the zero's are at the same end and, if looking with inches at the top, then flipping the rule over bottom edge over top (thus keeping the zero end in the same place) they are still marked with inches at the top.

Why FFS? I can think in either inches or cm as things require but sometimes the orientation of the job/ruler/edge means you can only get one scale in the right position to make an accurate measurement. If that is the "wrong" units for how I want to work at that precise instant I would like to be able to just flip the ruler to get the "right" units but nothing I have found is marked so as to allow this. 

[testian]

I was building a pwm circuit with a microcontroller (28-pin DIP) on Stripboard.
Everything finished, tested and it is working. Then I disconnected the circuit from the power supply without switching it off. Put my circuit back on the table directly on the non insulated banana plugs -> magic smoke escaped.

[Luminax]

Made a few short jumper using leftover LED legs... shifted a few jumpers around etc, change circuit layout etc...
And then my PIC stopped working... and I smell... MAGIC SMOKE! 
one of the pin had fell off the top bench and accidentally lodged itself magically in the breadboard... shorting VCC and one of the I/O pin and boom(well... no boom... and no camera capture sadly  )

[mclemens1969]

I break things now and then.

1) I smoked my uCurrent on the first use. Still not sure how this happened.

2) I fed 12V to a $95 electroluminscent display for its 5V supply. That was the last time I used a red lead for misc. V+ from the power supply.  It made smoke immediately, and included a celebratory noise.

3) I was pushing a $30 OLED into a breadboard (1x20 header) the other day and didn't keep even pressure enough -- snap right down the glass.

4) About 20 years ago I wrote the software in a robotic FDA approved orthopedic bone lengthener. One of the movement rates and rhythms available was later found to be wrong. I forget how wrong.

5) About 35 years ago we hacked into the school district computer. We kept dialing in even though one day all the access numbers (except for a single one) started being busy all the time. And why do you think only one number was left working??

[Rerouter]

5
Your telling me honeypotting was done back in the days of dialup? By school admins?

4 sounds very interesting.

[dimkasta]

I had just dismantled an old washing machine, and I had found a nice small but beefy motor on the mechanical program rotor. It would be a nice addition to my scrap box.

After a while I got bored and went to watch some Thundercats, having the motor on my hands, clicking it bit by bit just for fun.

Now, this was deep summer. And here in Greece deep summer means you are sweating a lot, and when you are watching cartoons you are probably just wearing your underwear.
So here I am watching Lion-o, feeling extra happy from the nice clicking sensation. It did not register on my brain that the wires were touching my belly until I decided to give the motor a big fast spin...
I jumped almost a meter high, and the motor flew off my hands landing on the other side of the room.

And yes we spent the rest of the week with my friends zapping each other