Tuesday, July 24, 2012

Make: Electronics - Experiment 17 (Part 1)

This experiment from Make: Electronics is really interesting as it introduces a 555 timer chip in both monostable and astable modes. This is what my breadboard looked like:



My challenge with this experiment, though, is that I had to spend a long time trying to troubleshoot two issues:
  • First, when I power up the second chip directly to go into astable mode, sound would not come out of the speaker until a few seconds later. According to the book, it should come out immediately.
  • When chaining the first chip (in monostable mode) to the second one (in astable mode), sound would not come out of the loudspeaker either - while videos on the web showed the speaker working right after the push button for the first circuit was pressed.

SOLUTION: at the end of the day, I learned how to solve the problem through a video on YouTube (linked below). I had to use a ceramic capacitor (I used 100 nF) between pin 3 and the speaker to filter DC and allow AC. That fixed the problem right away.

Of course you must be curious as how it works, so rather than filming my breadboard, I embed a video that shows the same experiment in more details:



Thanks to Chris, who posted this video above, for helping out with this great tip. I submitted an errata to the book, so at least this could be mentioned to save other's time.
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