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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.

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Hands-on learning for makers.


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

LESSON 3

Revealing Resistance

A resistor is a little component that usually has stripes printed on it. All it does is resist the flow of electricity — but that can be very useful.

Supplies

  • 2 33-ohm Resistors
  • 3 Alkaline AA Batteries
  • 1 Three Battery Holder
  • 1 Miniature 5-volt Light Bulb
  • 1 Red Alligator Wire
  • 1 Black Alligator Wire
  • 1 Green Alligator Wire
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The colored stripes are a code telling you the resistance of the resistor. I will explain the code in a moment.

Experiment 3: Revealing Resistance

For this experiment, you need a “33-ohm” resistor with stripes that are orange, orange, and black.

Ignore the silver or gold stripe at the opposite end.

The wires at each end are called leads (pronounced “leeds”).

Put the resistor into series with your light bulb. Touch the resistor lead to the pin on the light.

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The resistor limits current and drops voltage, leaving less available for the light, which glows less brightly than if you touch the red alligator clip to it directly.

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Try putting two resistors in series. The light is even dimmer now. Electric current has to push through two resistors before it gets to the light.

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Try putting the resistors in parallel. Now the current can flow through both of them, so the light gets brighter — although not as bright as with no resistors at all.

Understanding the Resistor Code

Each of the first two colored stripes on a resistor tells you a single digit. The third stripe tells you how many zeroes to add.

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A silver stripe at the right end of the resistor means that its value is accurate within 10%. A gold stripe means 5%. Either will be okay in this workshop.

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Hold the resistor with its group of three stripes on the left.

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A resistor with orange-orange-black stripes has a value of 33 ohms.

DEEP DIVE

Make Presents: The Resistor

Make Presents: The Resistor

Simple, commonplace, and vital to our electronic world — take a closer look at the current-fighting backbone of circuitry, the resistor, in this classic video by Collin Cunningham from the Make: Presents series.

Ohms

Resistance is measured in ohms. The ohm symbol is Ω but in this workshop we’ll just say “ohms.”

Capital letter K means 1,000 ohms, so 2K is 2,000 ohms, 3.3K is 3,300 ohms, and 470K is 470,000 ohms.

Capital letter M means 1,000,000 ohms. So 2M is 2,000,000 ohms, and 1.5M is 1,500,000 ohms.

Sample Resistor Values

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Could you redraw these schematics including an on-off switch?

Could you add a double-throw switch that allows you to send current through a resistor or bypass it through a wire?

PRO TIP

Euro Style Schematics

Europeans don't use a decimal point in schematics. If you see 1K5 it means 1.5K. while 4M7 means 4.7M. Values less than 1,000 ohms use letter R, so 33 ohms would be written as 33R.

THINK ON THIS

How Did It Work?

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Two 100-ohm resistors in parallel block half as much current as one resistor. Their total resistance is 50 ohms.

If you’re wondering what happens to the current blocked by the resistor, it is converted to heat. There isn’t enough for you to feel it with your fingers, because these circuits use so little power.


Up Next!

Try a Transistor