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Shopping List

The easiest way to obtain parts for the nine experiments in this workshop is by ordering a kit. You can order your Easy Electronics kit and handbook bundle (including three additional experiments) from Maker Shed.

If you prefer to shop for parts individually online, I suggest sites such as ebay.com, mouser.com, digikey.com, or newark.com.

- copy:

Here’s a complete list of everything you need for the 9 experiments in this workshop.

Batteries

Alkaline AA size.

Quantity: 3.

Note: Do not use lithium batteries!

Battery Holder for Single AA Battery

With solder pins or PCB terminals. Eagle Plastic Devices part 12BH311P-GR or similar.

Quantity: 3

Battery Holder for Three AA Batteries

With solder pins or PCB terminals. Eagle Plastic Devices part 12BH331P-GR or similar.

Quantity: 2.

Miniature Incandescent Light Bulb

This item is sometimes sold as a “lamp”. The one that I prefer, pictured throughout this book, is rated for 5V and 60mA and has a ceramic base with two short leads. Search for JKL 7361 by JKL components, or CM7361 by Chicago Miniature Lighting, a subsidiary of VCC. If these options are unavailable, a very similar bulb is JKL 7362; it will use more current and will be a bit dim when used with a series resistor, but should work in the experiments. Another option is to use a 6V bulb rated for 40mA or 60mA; these usually have a size E10 screw-thread base, and require a matching socket. Search online for E10 6V bulb, and you will find scientific supply companies selling the bulb and socket for high-school electrical experiments. It may be less bright than an equivalent 5V bulb, but should work.

Quantity: 2.

Alligator Jumper Wire

Single wire with alligator clip at each end. Any length, but very short ones are more convenient (3" to 6").

Quantity: 2 red, 2 black, 3 green.

Slide Switch

Also known as a slider switch. To use it with alligator clips, it should be as large as possible, with pins widely spaced. This can be a problem, as most slide switches today are subminiature. I suggest that the minimum body size is 1/2" or 13mm long, minimum pin spacing 1/8" or 5mm. You want a single-pole, double-throw switch, which may be identified as SPDT, SP2T, 1P2T, or PDT. Examples of an acceptable switch are part number PM13B012 by Apem or L102011MS02Q by C&K Components. You will be switching very small currents at only 4.5V, so you do not need to be concerned about maximum voltage or amperage listed for a switch.

Quantity: 1.

Resistors, Quarter-watt, 5% or 10% Tolerance

You will need values 33 ohms, 1K, 10K, and 100K: 2 of each. Values 2.2K and 3.3K: 1 of each.

Transistor, 2N3904 NPN Bipolar

Purchase from any manufacturer.

Quantity: 2.

LED

Low-current type, tinted red. Avago or Broadcom HLMP-D150, or HLMP-D155, or HLMP K-150, or HLMP K-155, for a typical 1.6V forward voltage, 20mA maximum average current but able to respond to 1mA.

Quantity: 2.

Phototransistor

Lite-On LTR-301 preferred, side-facing NPN type, rated 5V. Alternatively Optek / TT Electronics OP550B. (The O at the beginning of this part number is letter O, the 0 near the end is numeral zero.) The component that you use must be able to pass a constant current of 3mA. If you find that a side-looking phototransistor has both leads of equal length, hold the component with the lens facing you and the leads pointing down, and the right-hand lead is probably the collector (more positive). If in doubt, apply power very briefly.

Quantity: 1.

Capacitors, Electrolytic

Rated 10V or higher. 1µF, 10µF, 100µF, and 470µF.

Quantity: 1 of each.

Capacitors, Ceramic

2.2nF, 10nF, and 100nF. (These values may be written as 0.0022µF, 0.01µF, and 0.1µF.)

Quantity: 1 of each.

7555 Timer Chip

Preferred manufacturer is Intersil. If you try using a 555 timer chip, it will consume more current and may not work well at the low voltage in the experiments in this book.

Quantity: 1.

Mini Breadboard

17 rows of holes or more.

Quantity: 1.

Jumper Wires

22-gauge, stripped at both ends, in colors red, green, and black.

Length of insulation 1/2": 3 of each color.

Length of insulation 1": 2 of each color.

Piezoelectric Audio Transducer

With wire leads, DB Unlimited TP244003-1 preferred. Alternatively, CPE-827 from CUI Inc. If you search online, note that piezo is often used as the abbreviation for piezoelectric, and you should search for “piezo speakers” to avoid finding other kinds of transducers, some of which work like microphones. If making a substitution, larger is better (minimum diameter 1" or 25mm).

Quantity: 1.

Optional Items

Laser Pen

Used for triggering phototransistor.

Quantity: 1.

Magnifying Lens

Useful for reading part numbers).

Quantity: 1.

Nail Clippers

Used for trimming unruly component leads.

Quantity: 1.

Wire Strippers

For if you’d rather make your own jumper wires.

Quantity: 1.

Credits + Acknowledgements

Workshop author image
Charles Platt Author

Charles Platt is a contributing editor to Make: magazine and author of the bestselling book Make: Electronics. Formerly he was a senior writer at Wired magazine.

Explore all of Charles’s books here at Platt Electronics.

Lesson credit image

Hands-on learning for Makers.


This workshop is adapted from the Easy Electronics book and kit available from Maker Shed.

LESSON 7

Comprehending Capacitors

A capacitor stores electricity, as you will see in this experiment. It behaves somewhat like a tiny rechargeable battery, but it works in a different way.

Supplies

  • 1 470µƒ Electrolytic Capacitor
  • 1 100µF Electrolytic Capacitor
  • 1 Red LED, Low-Current
  • 1 1K Resistor
  • 1 10K Resistor
  • 3 Alkaline AA Batteries
  • 1 Three Battery Holder
  • 1 Double-Throw Switch
  • 1 Red Alligator Wire
  • 2 Black Alligator Wires
  • 3 Green Alligator Wires
Lesson main content image Some capacitors have colored cans. Others don’t. The color is not important.
Lesson main content image

Experiment 7: Comprehending Capacitors

This type of capacitor is called electrolytic. This one’s storage capacity, known as capacitance, is 470µF — but I’ll explain that in a moment. 50V is its maximum voltage, but for the experiments in this book, a capacitor rated 10V or higher is okay.

The short lead is the negative side, also identified with minus signs. Never connect an electrolytic capacitor to a power supply the wrong way around.

This is a larger circuit, so you can build it in two parts. This first part just charges the capacitor with electricity when the slide switch moves to upper-left.

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Some of the voltage from the battery transfers to the capacitor, although you can’t see any sign of it yet.

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Add the 1K resistor and the LED, with the negative side of the LED sharing the negative leg of the capacitor.

Now move the switch to the lower-right. The capacitor discharges itself through the LED.

Move the switch to the upper-left and wait five seconds for the capacitor to recharge. Now you can discharge it again.

If this diagram looks complicated to you, try sketching a copy of it, replacing the alligator wires with simple lines to connect the components. Or check the schematic at the end of this lesson.

Ceramics

Capacitors such as the one shown here are less than 1/2" wide. They are dipped in a ceramic compound. Most ceramic capacitors do not have polarity.

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Many ceramic capacitors have a code printed on them instead of their actual capacitance. Some are shaped like circular discs. In simple circuits of the type you have been building, usually you can substitute a ceramic instead of an electrolytic if you wish. Note that for values around 10µF and above, ceramics may be more expensive.

Farads

Capacitance is measured in farads, abbreviated with letter F. But a 1F capacitor is very large. In hobby electronics we mostly use capacitors rated in microfarads, abbreviated µF. The µ symbol is the Greek letter mu, but often µF is printed as uF. There are 1,000,000 microfarads in 1 farad, 1,000 nanofarads (nF) in 1 microfarad, and 1,000 picofarads (pF) in 1 nanofarad.

PRO TIP

Caps and Batteries

A capacitor may seem similar to a battery. After all, they both store electricity.

A battery, however, uses chemical reactions, and even a rechargeable battery wears out after a limited number of charging and discharging cycles.

A capacitor does not use chemical reactions, and can still work as well after several years.

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There are two symbols for capacitors: a polarized capacitor, such as an electrolytic, and a nonpolarized capacitor, such as a ceramic. Some people use the nonpolarized symbol everywhere in a schematic, and let you decide if you want to use an electrolytic capacitor, and if so, which way around it should be!

THINK ON THIS

How Did It Work?

Inside the capacitor you used are two pieces of metal film known as plates. They are separated by paste called an electrolyte, which is why this capacitor is called electrolytic. When electrons flow into one plate, they try to create an equal, opposite charge on the other plate. You can think of the plates as having positive and negative charges that attract each other.

Timing

The 1K resistor was needed because you charged the capacitor with 4.5V from the battery pack, and the LED can only handle about 1.8V. The resistor prevents the LED from being damaged. The resistor also controls how fast the capacitor discharges. Substitute a 10K resistor (brown, black, orange) and the LED is dimmer than before and takes much longer to fade out.

Here’s another thing to try. Go back to using the 1K resistor. Remove the 470µF capacitor and substitute a 100µF capacitor. Push the switch to and fro, and now the LED lights up very briefly.

Electricity moves fast, but a capacitor and a resistor can make things happen slowly.


Up Next!

A Simple Chip