Chapter 5 - Shopping List Update

Got a few more items in for Chapter 5 from various sources.


First, I purchased 10 germanium diodes and a single piezoelectric earphone from SciToys as the author recommended. Since I was paying for shipping, I ordered 10 diodes instead of just 1... I may never use them but they're not that expensive and I know a few people (including my dad) who are working through the book and I may part with a couple.

I couldn't believe I couldn't find these items locally - no Radio Shack that I called carried either the germanium diodes or the earphone and the few electronics shops I called carried the earphone but it was $10.00 and no germanium diodes.

Note: These items are NOT included in the Components Pack 2 - as a matter of fact, I'm finding quite a few things in the final experiments in Chapter 5 that are not included with Pack 2. (This isn't an error - Pack 2 states it is specifically for Chapters 3 and 4.) I'm trying to capture all the specialty items required for Chapter 5 and will see about making one final Chapter 5 shopping list that contains those items NOT found in Pack 1 or Pack 2. For example, Experiment 28 recommends a 4700 microfarad capacitor but the shopping list specifies 2000 microfarad minimum... if you're like me, you probably don't have any of these in your possession. Again, I'll try and go through Chapter 5 when done and pull together a complete list of specialty items.

Also, I picked up a plastic box for $1.50 at The Container Store... I was in the neighborhood and remembered that I needed one for Experiment 29.

From SciToys (www.scitoys.com)
10DIODES $7.86
EARPHONE $6.84

(Those are the actual part numbers above with the prices.)

Read More

Chapter 5 - Exercise 28

I'd never seen this application of a coil, but the theory you'll read about for Experiment 28 makes sense.

In the first part of the exercise, I simply wired up the circuit on page 247 and pressed the button. As expected, a single LED lit up on the button press and the other LED lit up on release of the button. It happens quickly. The author recommends against holding down the button because the resistor will get hot fast. You can see this in action in the first video.

The second part of the exercise involves hooking up a capacitor in place of the 220 ohm resistor (don't forget to add in the single 1K resistor). The author states that capacitance works the opposite of self-inductance, so you would think that based on the first exercise, we should see the 2nd LED (on the right in the video) light up first, and then the 1st LED (on the left) after the button is released. The second video shows my results.

What happened? As I understand it, capacitance resists at first and wants to take most of the current to charge up - so the first LED does light up, but not as bright. Releasing the button causes the capacitor to discharge and I can only guess that the resistance in the coil is very low (compared to LED 1) so the current flows through the coil and then through LED 2. Of course, I could be completely wrong as I expected LED 2 to light up first... then LED 1. Goes to show that electronics don't always behave in the ways we expect them to... (or maybe I wired up this modification incorrectly - if anyone knows, please let me know so I can try again.)

A fun experiment... just be sure to wire up that capacitor correctly (for polarity).


Finally, I got my copy of 'Practical Electronics for Inventors' by Paul Scherz. A quick scan of the entire book and a read of the first few pages tells me that although the material is quite dry (compared to Make: Electronics), it should be very useful. I can already tell that this book should be easier to read and understand after having completed Make: Electronics.

Read More

ePub digital edition - Update

Thanks go to Seth over at O'Reilly Media, Inc for emailing me an updated version of the book - as you can see, the cover looks great on my iBook shelf.

Read More