I ran a business in elementary(! 10-12 years old) school selling self designed junk. All pre 1989 Poland, so still under Soviet occupation = no good western toys in shops.
It started when I build cable remote controlled buggy from: tape deck parts for motor and cogs (gearbox reduction was all made and designed by me using those cogs, nails, pcb and epoxy, I was so frickin proud of it ), pcb for base plate, thick copper wire for frame and front steering, scotch tape rolls pushed into bike rubber tube for rims with tires, flat ribbon cable to the remote, plastic box filled with two 4.5V batteries and glued dip switches as the remote . As soon as I showed it off on the school playground one of the rich kids offered me a ridiculous sum of money, something like 1/5 my mums salary at the time. After that I made one more electric toy and switched into electronics. I discovered CD4000 series chips manufactured locally(CEMI) and fell in love, had whole notebook that I manually filled with handwritten datasheets and designs
Long story short my bestseller was a CD4060 based TIMER that I marketed as a TIMED DETONATOR ('just like in the movies' TM). With a blinking led and everything, last stage of the counter was connected to transistor driving crushed flashlight bulb, designed to detonate firecrackers. Of course as part of making it extra double cool I sanded off all the markings from the components, giving it that extra terrorist touch.
Thankfully nobody used it with actual bomb (afaik).
That's awesome! I love your ambition. What did your mom think when you made that much cash selling something you made?
I started thinking about this clock-bomb story it dawned on me, if I were a kid today, I would have been arrested too!
I remember making a 555 based countdown timer from a Forrest Mimms book and bringing it to school in 4th grade. It was on a piece of perfboard, hand soldered with wires running everywhere.
In 5th grade we had an assignment where we had to teach the rest of the class how to make something, so I created a simple monostable vibrator out of transistors to blink an LED then hand etched 25 small copper boards with the circuit. I brought all the components into school and taught the class the basics of how transistors, resistors and capacitors worked (using the water analogy), how an LED was different from a light bulb and a basic idea of how the circuit functioned.
Then everyone would assemble the circuit and bring it up to be soldered. (I had a friend who knew how to solder help, so we could get through 25 boards quickly.) As an option, they could wait until recess and I would teach them how to solder the board themselves. I had 3 people take me up on it, all girls. (I think they liked me, but I was too dense to see it back then.)
So, I guess you could call that "The time I taught a class of fellow 5th graders how to make a bomb timer." (I got an A+ plus extra credit for my assignment too!)
Then, there was the time in 3rd grade I brought my homemade rocket launcher system in for show and tell. It was an old small suitcase with a plywood front panel, underneath was two 12V lantern batteries and a mess of wires. It had banana jacks for connecting the igniter cable, a key interlock (literally a car ignition switch salvaged from old car parts my dad had), a 12V analog meter to measure the battery, a warning piezo buzzer and a rotating yellow hazard light on the top. Plus switches and buttons to set the automatic timer.
This huge complicated thing to launch $5 model rockets! Yeah, I'd be in jail today.
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