Chapter 5 - Exercise 26

This was another fun little exercise that I've seen in various forms over the years... the picture on page 241 (Figure 5-22) really does hammer the concept home - given the right components, you could create something to generate a sufficient amount of voltage to power a lightbulb or other low power device. Of course, I'm not sure where you'd find a magnet of sufficient size to make this experiment bigger (or safer) but the theory does make sense.

A few notes...

I wish I'd purchased a slightly wider diameter magnet than 3/4" - the hole in the center of my magnet wire spool is a little over 1" in diameter... a 1"diameter magnet would have been perfect. The 3/4" I had worked, but it bumped the spool and wasn't as easy to move up and down as a magnet that was a tighter fit.

Also, don't forget to sand off the ends of the magnet wire - I forgot about the little bit of clear insulation over the wires and didn't get any results at first. You can see in the first video that I eventually do get the red LED to light up. (FYI: I connected another LED in the string and got both to light up at about half the number of blinks as a single LED... adding a third LED resulted in zero light.)

Next, I connected the 100microfarad capacitor as seen in Figure 5-23, with the diode properly oriented. The second video shows that I got up around 2.6 volts... a nice number! I didn't get close to the 10V the author mentions, but there are so many factors at play here that I'm sure I could have reached it with the right diameter magnet and spool hole.

As the author advises, be careful with these magnets. Fortunately my titanium ring that I forgot to take off wasn't attracted to the magnet. Of course, I didn't keep the extra LEDs and gator clips far enough away and was always having to pull them off. I finally got smart and started storing the magnet in a small plastic container by itself until needed.