Education, Technology, Uncategorized

20,000 volts meets Watermelon

Many Davenport area students who trained in electronics during the late 1980’s will remember Mr. Del Terhune the Electronics instructor at West High School. He had a very special way of teaching occupational safety I will never forget.

Mr. Terhune taught the High School electronics courses at West High School. If you were very interested in electronics as I was, you had to take several courses  with him before you were allowed to take the vocational electronics courses. Davenport Community Schools had offered two years of vocational electronics. Its the only formal training I ever had, and served me well enough I made a career out of working with electronics. I no longer repair electronics for a living, but I sure love playing with it as a hobby.

Mr. Terhune was a real character, he often walked around in a ladies cleaning smock carrying a large capacity capacitor. A capacitor is in about every electronic device you come into contact with. Large capacitors are common inside of washers, dryers, air conditioners and microwaves.

Capacitors store a charge, that is their function and they are so very common that Mr. Terhune wanted to leave an impression on his students about how dangerous they could be.

Capacitors can actually collect a charge just from the static in the air around us. They don’t even need to be charge to give you a little jolt. As a safety precaution they are usually stored with a conductor shorting the terminals to ensure they will not build up a charge. Suffice to say you need to use some care around them, and treat them with a little respect. 

The high school level electronics classes often required that students worked quietly and independently on projects that involved the mathematics of calculating component values in various configurations. It was often very quiet in these rooms, you could hear a pin drop.  Since these were classes designed for those probably not college bound, these were practical labs, sometimes setting up complex equipment.

Most of the voltages were safe, but required close inspection before we were allowed to apply the power. Mistakes were often known to free the magic smoke stored inside components, you know that magic smoke that makes all electronics function. Let that smoke out and, no-worky.

Mistakes were often known to free the magic smoke stored inside components, you know that magic smoke that makes all electronics function. Let that smoke out and, no-worky.

While Mr. Terhune was walking around the room, he often carried a large capacitor with him. As he approach  he would ask “is this capacitor charged, or discharged”.  It was an object lesson that none of us would ever forget. Since you can never know one way or the other.

After your answer, he would simply touch the terminals of the capacitor he was carrying to the steel grey desks we were seated at. Sometimes nothing would happen, an apparently discharged capacity, maybe that day it held no sparks, or the room lighting was simply too bright to allow you to see them. Other times we were met with an explosion and the loud SNAP that those who have worked with them learn to recognize. This is usually coupled with a bright flash and the wiff of smoke.

I will never forget this lesson of capacitor safety and when I saw the video of capacitor meets watermelon I couldn’t help but think back to this most important lesson in occupational safety.

If you had Mr. Terhune as a teacher, or have a story to tell about coming into contact with a capacitor, or other explosive technology stories, please share you stories in the reply section below. I would love to hear from you and about your shocking experiences.


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