Electronics Projects Gone Bad

Our readers shared their stories and learning experiences about how even though you have the perfect solution not all electronic projects may go as you has planned.

Just Not Giving Up

When I was in the third grade, our teacher demonstrated how a door bell worked so we could follow the electric current. I was so fascinated with this that I burned with the need to try the same experiment at home and show my family my new found knowledge. So after school I ran home to the basement to find all the necessary components in my grandpa's junk box.

I found a bell (12 volts DC), an old cheater cord (lamp wire with a plug at the end) BUT no 12 volt battery. I asked mom if I could buy a lantern battery so the family could see my experiment. She told me to go to the hardware store and ask what it would cost. Well, it cost $9.50 and in 1959 it was a great deal of money for my working class family. Mom said it was too expensive, but a smart kid like me could probably find another experiment.

Leaving this disappointment behind me, I looked in basement again for a big battery, no luck! But I saw the cheater cord and voila! I called my little brother to the basement and told him that he should block his ears because he would hear the loudest bell ever. I reasoned that if 12 volts of DC made the bell ring, 120 volts AC would make it ring 10 times louder ( I was 9).

When I plugged the bell into the power outlet, the hammer of the bell got spot welded to the bell, and the contacts were sparking like crazy. The power outlet was burnt, and I blew the fuse in the panel. The only thing my mom noticed was that her kitchen radio stopped working. My dad replaced the fuse when he got home from work. I didn't see any reason to tell them anything more about how it might have happened and I successfully silenced my brother. But there was something about the way dad smiled at me that left me wondering if I had actually gotten away with it.

--- The Experimenter

Million Dollar Magnet

I was in my 7th and final year working on a PhD in atomic physics. My university was pushing me to finish so I worked every day in the lab along with one all-nighter a week. My research required me to revive a 5 foot tall, 800 pound, 10 Tesla superconducting magnet that my research advisor had bought for a million dollars ten or twelve years before.

After one all-nighter, I had to line up the vertical bore hole with a hole in the bottom of the wooden box that supported it. I thought that I might hoist the box up, lower the magnet onto our biggest ring stand, which had a 1/2 inch steel post, and swing the box into position under the magnet. I didn't trust my own judgment since I had been up all night, and our research advisor was never around, so I discussed the plan with another grad student in our lab, and asked him to help.

As I was lowering the magnet onto the ring stand, I noticed that the steel rod was noticeably bending, and dreaded what would happen if it broke or slipped. So, I told the other grad student, "This is a bad idea. I am hoisting it back up." I had just started to hoist the magnet back up when I heard a crack like a gun shot, a clang, and then a hiss. The crack was the base shattering into three pieces which I found later in 3 corners of the lab. The clang was the rod sucked up into the borehole. The hiss was liquid helium escaping. A leak had formed in the vacuum jacket, so it would no longer hold liquid helium. Thank God no one was injured.

Over the next few weeks, I tried to locate and mend the leak. I needed to bake the magnet, so that it would have a good enough vacuum to hold liquid helium. I phoned the company that made the magnet and was advised to keep the temperature well below 18°C. The vacuum got worse rather than better with baking. I found that the magnet was wrapped in thousands of layers of mylar sheeting, which had split due to the high temperature. The million dollar magnet was effectively destroyed.

My research advisor then told me to defend an MS and leave. I had already published significant experiment in that lab in Journal of Physics B, and I wrote my research advisor a letter detailing why I deserved the PhD, but my research advisor was the department head, and he got the other top researcher in atomic physics at the university on his side. The dean had no background in physics. So, I defended an MS and left. I never got the PhD, but I do General Relativity and Quantum Relativity as hobbies.

--- Joseph D. Rudmin

Low Quality Capacitors

When I first got out of the military too many years ago to repeat, I wanted to build an electronic kit. I ordered the Heathkit high voltage power supply kit and proceeded to build it. It took me about a month to build, and when it was done I just couldn't wait to plug it in and turn it on. Turns out I should have waited.

Smoke started filling my house and the boom that followed shortly after that definitely scared my wife more than me. I couldn't do anything but sit there with egg on my face. The problem was blown power supply filter caps. I had hooked everything up correctly, but I noticed that capacitors appeared to be a low quality, so I went to my local electronics store and purchased 2 new ones. I never got the egg off my face, but I did fix the problem, and I still use the power supply frequently.

--- Tom Turner

Electrical Interference

In the 1970s, 7400-series TTL logic devices were the best way to implement sequential controllers. You would drive a counter with a clock signal, typically derived from the 60Hz power line, and use logic to decode the times at which you needed to turn on a relay to activate some device; or to reset the counter back to its initial state. One of my colleagues needed a simple controller like this to emulate pushing buttons on a large mechanical tester. I built him such a circuit, we tested it, and it worked well.

Several months later he called me to say that my circuit was activating his mechanical tester at odd times. When I went to see what was happening, I saw that he had added a hefty furnace to the tester. The furnace was controlled by a huge relay that emitted giant blue sparks when it operated. All this electrical interference was causing logic glitches in my circuit. I put a suitable capacitor across the relay contacts, and this fixed the problem.

--- Dev Gualtieri

WARNING – Do Not Try This at Home!

I built a 100,000 Joule seismic system that consisted of a bank of nine parallel capacitors encased in a rugged welded steel case charged to 4,000 V-Yes 4,000V. During testing one of the capacitors failed to discharge. We took it gingerly out of the rack and tried to discharge it by shaking it to no avail. But how to destroy it?

If it suddenly came alive, the trash collector would get the shock of his life. So, we decided to dispose of it ourselves. We took it to a big open field along with a 30-06 rifle. One shot and the whole thing disintegrated into little bits and pieces blowing chlorinated bi phenyl all over the place. Fortunately we were a good distance away. The supplier wanted it back before they would refund or replace. We sent what was left, along with a warning label. As far as I know grass has never grown in the spot of detonation.

--- Jay Harford