Your stupidest mistakes

[GarthyD]

Early on while still learning, I reorganised part of a circuit on a breadboard and inadvertently flipped VCC and GND on a temperature sensor.

One trick I had read about and used repeatedly when testing temperature sensors was to press your finger firmly onto the device, which will cause the reported temperature to rise slightly.

Little did I realise that when left alone for a while with reversed polarity, the temperature sensor I was using got very, very hot.

So, whilst debugging my code which had suddenly stopped working, I pressed my index finger firmly onto the burning hot device.

Lesson learned.

[meeko]

Just remembered another one from back in my high school electronics days...

We didn't have proper stands for the soldering irons, just a bit of stamped metal to prop the element on to keep it off the bench.

One day, I was soldering up a project, went to pick up the iron after placing my next component, and ended up trying to pick it up by the element!  And not just brushing a finger against it, or anything.  This was a full-on, close your whole hand around it, grab.  I highly recommend avoiding doing that...

[ohdsp]

I couldn't get the circuit in the attached schematic to work for some reason, spent ages building up 2 PCBs as well! 

[eugenenine]

Just remembered another one from back in my high school electronics days...

We didn't have proper stands for the soldering irons, just a bit of stamped metal to prop the element on to keep it off the bench.

One day, I was soldering up a project, went to pick up the iron after placing my next component, and ended up trying to pick it up by the element!  And not just brushing a finger against it, or anything.  This was a full-on, close your whole hand around it, grab.  I highly recommend avoiding doing that...

Did that one myself.  Promptly went out and bought the $30 stand one from radio shack and took it to school when we needed to solder.

[David Hess]

One day, I was soldering up a project, went to pick up the iron after placing my next component, and ended up trying to pick it up by the element!  And not just brushing a finger against it, or anything.  This was a full-on, close your whole hand around it, grab.  I highly recommend avoiding doing that...

I can do better than that; I reached over the iron which was lying on the bench and set the soft part of the inside of my arm down on the thick part of the barrel ... and it stuck.  30+ years later and I can still see the discoloration where the scar is.

[eugenenine]

How many of you, when first starting out. would get too much solder on the tip then flick it off?

I dropped a big ball of solder on my leg

Was wearing shorts

I'm over 40 now and can still see the scar.

[cheeseit]

25 years ago as a kid I was using an iron where the stand was a short length of steel tube held in a vise. While reaching over it the underside of my wrist came to rest on the tube, however shortly, resulting in the familiar sizzling sound and a smell of burned skin left on the tube. It hurt like hell and the scar is still very visible.

[dimkasta]

I have done the same full hand grab on my first iron.
Thankfully it was one of those with the plastic cover which I used when soldering too. The pain was intense but thankfully there was no sizzling or scar

[grumpydoc]

How many of you, when first starting out. would get too much solder on the tip then flick it off?

I dropped a big ball of solder on my leg

Was wearing shorts

I'm over 40 now and can still see the scar.

Not electronics but I was soldering a capillary plumbing joint last year where the angle of the pipes, walls and joint meant that I was holding the blowtorch directly under the joint.

Unfortunately I over-filled the joint and the excess dripped out of the opposite side.

All over my hand 

Lead free as well (no choice with EU regs).

[@rt]

Opening 90% of webpages that say they provide datasheets

[djacobow]

Opening 90% of webpages that say they provide datasheets

Ha ha. I know the feeling. When I'm looking for a datasheet and the link isn't to the actual manufacturer's site, I only click if I am in deep desperation. And I am never rewarded.

Honestly, I wish there was a Google option to tell it never to show me those sites ever again. They're Lucy with the football.

[tautech]

Opening 90% of webpages that say they provide datasheets

Use: device data pdf
Cuts down on the false hits. 

[Rerouter]

At the bottom of the google search page is the option to "send feedback" if we hit the BS sites enough they should be deranked off the first page.

[ale500]

I don't remember if it was late at night or no, but what I remember is:
I had this Brazilian TK85 (ZX-81 clone but with a discrete ULA), I though I'll remove the regulator (7805) and power it directly with 5V. I didn't know it needed 12 V for the DRAMs. I was using a switching power supply with several outputs, -5, 5 and +12, that where more like 14 V. Of course I powered it with 14 V instead of 5. The noise the ICs did when they melted is something I haven't forgotten. It was 27 years ago...

[BradC]

Not electronics but I was soldering a capillary plumbing joint last year where the angle of the pipes, walls and joint meant that I was holding the blowtorch directly under the joint.

Unfortunately I over-filled the joint and the excess dripped out of the opposite side.

All over my hand 

I got so sick of capilliary plumbing I bought a small (tiny) oxy-propane setup. Now all my plumbing is silver-soldered. No drips. Having said that, when you heat up a copper tee to a nice red heat to un-solder it, then drop it on the floor and tread on it in bare feet the smell of burning skin is pretty overwhelming.

[grumpydoc]

I got so sick of capilliary plumbing I bought a small (tiny) oxy-propane setup. Now all my plumbing is silver-soldered. No drips. Having said that, when you heat up a copper tee to a nice red heat to un-solder it, then drop it on the floor and tread on it in bare feet the smell of burning skin is pretty overwhelming.

French plumbers (as this escapade was in France) tend to hard solder everything and often fashion joints manually - all beyond me at the moment. Thankfully capillary fittings are easy enough to find.

It sounds as though you would fit right in with the "proper" way of doing things. 

[ZeTeX]

I once had this great idea in 3AM to experiment with high current through a coil to see if I could heat it up nice.. yeah whatever I did I managed to get a burning mark from a 5W red hot resistor, then from the panic drop the resistor to the ground then step on it with bare feet while it is still extremely hot. and somehow I also got other burning mark from something else the same day.

best day ever.

[fable]

When I was a boy

[Cubdriver]

   I bet you only did THAT once!! 

-Pat

[bsudbrink]

Early on, I got a bag full of mixed LEDs that were "not all guaranteed to work."  I sat down with a 9 volt transistor radio battery, quickly tapping the leads of the LEDs to the terminals of the battery... no current limiting resistor   Blink, good, no blink, bad.  I got away with it for a while. Then I was distracted for a few seconds with the LED touching the terminals.  It popped like a little fire cracker.  I was picking bits of red plastic out of my thumb and finger for several days after.

[Tom45]

Early on, I got a bag full of mixed LEDs that were "not all guaranteed to work."

After your test, they would have been "all guaranteed not to work". 

[bsudbrink]

Early on, I got a bag full of mixed LEDs that were "not all guaranteed to work."

After your test, they would have been "all guaranteed not to work". 

Surprisingly, no.  I used a number of the ones that passed my "tap test" in various projects.  They all worked fine.  We're talking big old 1970's "top hat" LEDs.

[bji900]

Early on, I got a bag full of mixed LEDs that were "not all guaranteed to work."  I sat down with a 9 volt transistor radio battery, quickly tapping the leads of the LEDs to the terminals of the battery... no current limiting resistor   Blink, good, no blink, bad.  I got away with it for a while. Then I was distracted for a few seconds with the LED touching the terminals.  It popped like a little fire cracker.  I was picking bits of red plastic out of my thumb and finger for several days after.

Kinda like the proverbial fuse tester I knew it was a good fuse...

[m98]

Once I did kind of a show demonstration of high voltage and plasma physics, also consisting of a demo of lowering the breakdown voltage of air by ionizing it with a flame. Well, guess who ended up throwing a bunsen burner a few meters across the room? At least nobody slept in during that presentation anymore...

A less dangerous one, never trust in the correctness of late-night designed PCBs. Just finished assembling a board where I forgot to add output capacitance to a linear regulator, noticed the mistake as some ICs released their magic smoke.

Also an all time favorite, mismatched LED-Datasheets and subtle pinout variations in jellybean parts.

[dimkasta]

Spending hours staring at a PCB and schematic verifying you missed nothing.
Then notice a mistake on PCBs or think of a new awesome feature a few minutes after submitting the gerbers for the prototype.
And then just start spamming emails in a hurry hoping that you are lucky enough to not have any issues with time differences and manage to find someone to update the files before production begins.