(Confess) Your stupidest electronics related mistakes.
Martin Hodge
Posts: 1,246
Bet mine tops them all:
Trying to solder with a spool of hookup wire. "Why won't this iron get hot enough?! What's that smell..."
Trying to solder with a spool of hookup wire. "Why won't this iron get hot enough?! What's that smell..."
Comments
Many-times-stupid: Forgetting to slide on the shrink tubing or connector housing before soldering the connector.
-Phil
My personal favorite mistake was when I was wondering why a circuit board was glowing red, "I'm sure there are no LEDs on that board" I thought. Turned out to be an EPROM I had plugged in backwards the chip glowing red through the little window.
Then there's the classic ... realizing after you've made all of your solder connections, that you forgot to slide on the heat shrink tubing.
EDIT) I forgot this one.... you read, and it it might explain why I tried to suppress this one ... REALLY REALLY DUMB
Me and a friend of mine got a hold of a microwave oven transformer... we decided to plug it in "free-style" and how fun it was to 'vaporize' random components lying around the workbench. Until I managed to get hold of BOTH ends of the secondary on accident. The next thing I knew, we were both on the floor. My muscle jerk reaction was enough to knock both of us out of our chairs (bar-stool-type) and on our butts. I think I de-fibbed myself in the process.
It took many years for me to accept the fact that I should first check the circuit board without it being populated by the ICs. Lots of fried components from solder bridges and wiring errors.
There are things I have done that are more embarrassing, but certainly not as stupid.
Not checking for shorts before switching on a board.
Switch on a board on the table with solder wire below... or bare wires, or forgotten resistors.. or any other conductive junk.
Switching the polarity in a hurry, after having spent time indicating polarity with big coloured polarity indicators.
@RDL2004, gee I have a similar breadboard.
@Loopy, testing in phases is probably one of the things we should stress most to those new to electronics. "You CANNOT put the magic smoke back in..."
C.W.
I had a similar experience. I was in my parents attic attempting to run another line from an existing cable. I cut the power off at the circuit breaker box - partially anyway. I did not know that the wire had TWO live circuits on two different breakers! I almost fell thru the ceiling plasterboard and the pliers were welded shut...
Similar to leaving off the heatshrink, I have frequently soldered a phono or headphone plug only to realize that the plug's cap was still laying on the work bench...
Or soldering on a connector before fishing the wire thru the hole in the project box.
Then not my error, but I found a problem when I was an electronic tech that 1uf capacitors were suddenly being installed on all circuit boards instead of .1uf capacitors. I went to the assembly lines folks and pointed out the error. The supervisor said they ran out of the .1 uf caps, so were using the 1 uf caps instead. She said "They are the same aren't they?"
Haven't been bitten once in 30 years, and I sure hope I didn't just jinx myself. Not recommending this to anyone, BTW.
ZZZZZAAPPP!
That was probably what is called a MWBC or Multi-Wire Branch Circuit. It is two separate 120 volt circuits which share the same white neutral wire. The National Electrical Code now requires the breakers for these circuits to have a tie bar - like with two breakers on a 240 volt circuit. Then you must turn off both breakers.
MWBC...
(See Multiwire branch circuits)
http://ecmweb.com/nec/code-basics/electric_branch_circuits_part/
That cable was installed by an electrician back in the late 60's to add new circuits for window air conditioners.
The breakers were not adjacent so I figured he was lazy - or just incompetent.
I was in High School and knew that the breakers should have been linked.
I do that too but I have been zapped many times and ruined a few screwdrivers...
I used to test for a live circuit by quickly flicking it with my finger (120 only - never 240!!!) O_o
Like you, I am not recommending this for anyone...
I also used to strip spreaker wire with my teeth - don't do that any more
But the top of the list happened in high school. I was building a nitrogen laser using the plans from Scientific American and it needed a high voltage low current AC power supply. The plans called for a used an old automotive starter coil, and copper clad PC boards for a giant capacitor. I followed the wiring diagram carefully and it worked! I know this because it arced and discharged into my hand which went numb for a minute. Luckily it was powered by batteries so the total power was fairly low.
It scared me so much that I never finished the laser, but I still have the components in my garage. After that experience I've never worked on live AC wiring.
Problem:: I never hooked up the ******* DC!!
Embarisment: I didn't show up for 3 days!
FYI - If it has a "shared white neutral wire", then the breakers need to be on opposite phases - typically next to each other like a 240 volt circuit. Otherwise there is a danger the shared neutral will overheat if it is the same gauge wire as the hots. This works the same as the 3 wires coming into a house all the same gauge. An equal load on both circuits will "cancel" each other out and there will be little or no current flow through the neutral. But if both circuits are on the same phase, then the current flow on the neutral would double and exceed the capacity of the wire (heat).
I now put a line of text on every layer of board I build!
More recently, building another PCB in expresspcb, went to do the proto etch at home, printed it on press'n'peel, etching, drilling, only to find that none of the ICs fit. Turned out that when I printed the image the printer driver subtly resized the image!
I now test layout the most complex compotent to ensure there is no skew and that it all fits.
The following one is not mine, I remember reading in an electronics mag how they'd had an issue with someone building their VHF radio kit (all discrete, requiring hand wound coils, etc). They indicated that the person had perfectly built the unit, but it didn't work no matter what troubleshooting steps they told him to do, first in the magazine feedback column, then in letters and finally on the phone. When they finally saw it in person they found that he'd used perfectly shaped blobs of epoxy glue instead of solder!
There was also an input for a panel pushbutton switch to tell the scale whether to enable another output driving the outside scoreboard display. We used the same wire, Belden 8723, for this input as for the serial connection. Except the scoreboard control was 110 VAC...
You know what's coming next. Working too fast I wired the scoreboard control in parallel with the serial inputs. It worked fine when I powered it up, unaware that I had converted the scoreboard control switch into a "Push to destroy $10,000 worth of equipment" button.
Oddly enough, the manufacturer honored the warranty.
I was about to order a replacement unit, but I removed the reader and discovered that one of the traces on the PCB burned off like a fuse. I soldered in a replacement wire bridge and all's well now.
Keep my chair leaned over on the floor, and don't keep change or washers on the desktop!
I built some driver boards for my IGBT's and test each stack (pair) for proper operation and after wiring together all 3 sets I got in a hurry, I loaded my propeller driver and hit the switch to the 24 v bat.
It made some beautiful fire works ... and I'm fairly certain I generated the 4th state of matter ... unfortunately, I wasn't filming (too much of a hurry). So I made a sketch of what came out of the top of the chip.
It visually appeared in a blink of an eye directly over the top of the IGBT and did NOT move (or flicker), it made noise and you could feel the 'heat' on your skin.
I pulled the emergency cut-off switch, and examined the IGBT ... I had went back and re-soldered a gate resister, and in the process (one board only) created a solder bridge, that kept the top IGBT gate 'ON' all the time.
I should know better than to get in a hurry ... 'You only rush to disaster'.
I had one connector all wired up for some project, complete with 12V power supplied to one of its pins.
The project got its signal from my laptop's parallel port through another 25 pin "D" connector.
I finished up the final wiring, grabbed a "D" connector, plugged it into the laptop printer port, and experienced one of those "Oh sh%^&t, did I just do that" moments. The 12V instantly fried one of the laptop parallel port output bits.
I'm trying to improve my reputation!!!
hooking up a linear regulator backward, I noticed it wasn't outputting any voltage and got really hot, no major damage though
the usual "forgetting to put the heatshrink on before soldering the wire"
trying to solder with a paperclip instead of solder
Not my mistake: At my school's electronics lab there are a few soldering iron holders that look like this(http://www.gausbach.de/solder.jpg) and some guy put a sponge in the box where the hot iron tip is held. Due to the structure of the holder, the sponge was not seen by the next person who used it. Then, the sponge dried out and caught fire. Surprised the guy using the holder, but nothing really bad happened.
Finally, although not exactly an electrical mistake, I lost control of a pneumatic actuator. I was testing some servo controllers on the actuator when one of them malfunctioned. It made a lot of noise, and I now keep the shutoff valve within arms reach at all times.
Reading all these stories of blunders from experienced engineers makes me want to return to gas light and steam power, or at least stick to software.