May 25, 2015

Intro 02: Where Do I Start? With Parts and Stuff?

In My Early Days

...I didn't buy too many parts. Maybe just a few "Archer Surprise Paks" from Radio Shack.

I got most of my parts by taking apart old stuff. Cassette tape recorders, AM/FM radios, can openers, and so on. They were old and broken. I think they were broken. Well, they were after I took them apart!

Today, I don't expect most of you to start off this way. New parts can be bought at a very low price and with fast delivery. But my inner scrounger still lives on. Throughout this blog, I'll mention such 'cheapskate' options.

Building Your Own Inventory

My list below is a starting point. It's very basic. It has the most commonly used items, which can be used to do many projects. If you are very new to electronics, building the very simple circuits can help you see if you want to do more. Advanced projects may call for a specialized part or tool. Some specialized parts which are not listed here include fans, transformers, connectors, motors, rotary switches, LED or LCD displays, photocell optical sensors, special hardware, and special semiconductors (diodes, transistors and integrated circuits).

Getting Specific About Parts

Every part is a certain type, and has a value and a rating. The type, value and rating of each part makes it different from another part — unless all 3 are the same. For example, a "2N3904" transistor and a "2N3906" are both transistors.

Transistors
2N39042N3906

They look very much alike. Same size, shape, color. But they do not work the same way. They are not the same exact type. You must read the markings to keep them apart. (Once you get more serious about electronics, you might buy a special meter that can help identify them and test them.)

You cannot substitute one value for another. A bad substitution can damage the part and also other parts in the circuit. Follow the instructions about making substitutions, or wait until you learn more about values, ratings, and types of parts. And be careful not to mix up your parts.

Actually, there is one kind of substitution that's worth explaining. Some parts come in different sizes, but they still work the same way (mostly). The different sizes could be called small, medium, large, etc. Well, they're not sold using those words. Resistors come in a range of power ratings. Capacitors come in a range of different voltage ratings. And a higher rating usually means a bigger size. Our circuits use very low powers and voltages, so you can use almost any size you like. I recommend a larger size if you're not used to handling and identifying small parts. More details below.

Easy Markings

Parts are usually labeled in some way to show their value. For some parts, the labeling is clearly spelled out. In the example above, a "2N3904" transistor should have "2N3904" marked on it for you to see. Large Capacitors — the kind with "+" and "-" leads — have numbers and letters printed on them, like "10μF / 35V". The "10μF" is the capacitor's value of 10 microfarads (I explain what this means below). The "35V" is its voltage rating of 35 volts (it will be damaged if it gets more than 35 volts).

Even the 35-volt version may be a little small to deal with. If you're not used to handling small parts, you can get the 50-volt version of these "large" capacitors.

Large Capacitor, 10 microfarads

Resistors and small capacitors are another story.

Resistors

Resistors usually have color stripes to mark the resistance value. (Why stripes? So inspectors could see them no matter how the resistor was installed in the circuit). Until you learn the color code, keep your resistors organized and separated by value! Resistance value is measured in ohms. The large Greek letter omega (Ω) is the symbol for ohms. Resistor values range from less than 1 ohm to over 10 million ohms, and all be the same size. A bigger-sized resistor can handle more power than a smaller one.

The resistors in our circuits will see only tiny amount of power. So, we can safely use the common and easy-to-use 1/4-watt size. But the 1/4-watt size is small — only 1/4-inch long, and thin. For some people, this is too small to read its color bands without a magnifying lens, and too small to handle in one's hands. The 1/2-watt size is a little larger. The 1-watt size is big enough for just about anyone to handle — about 1/2-inch long, and thicker. I recommend starting with the largest size if you're not sure.

Inside a resistor is usually a thin film of either carbon or metal. Either type is OK. Carbon-film is cheaper and a good choice for beginners.

Resistor

Capacitors

Small capacitors usually have numbers and letters on them, like "102J". The "102" means it should have a capacitance value of 1000 picofarads. The "102" actually means 10x102 which equals 1000. The "J" is a standard code for +/-5 percent, so the 1000 picofarads value may be off by 5-percent more or less. That is, the actual value could be 950 to 1050 picofarads — but this is not important to the beginner.

The capacitor may be other markings on it, but they're not as important. The capacitance value is the most important. It is measured in farads. The large "F" is the symbol for farads. For a given capacitor formula, a bigger capacitor is usually has more capacitance and/or a higher voltage rating than a smaller capacitor.

There can be different materials inside capacitors. The material type affects their size. The large capacitors mentioned above are the aluminum-electrolytic type for our projects. They can provide a lot of capacitance in a small size, but must be used carefully. They are polarized (like batteries) — there is a "+" (plus) lead and a "-" (minus) lead. The "+" lead must be kept at the same or more positive voltage than the "-" lead or else this capacitor will be ruined.

The small capacitors are not polarized — there are no "+" and "-" leads. So they can go in a circuit with either lead in either connection. Inside, they have either ceramic or plastic-film. For beginners, either ceramic or plastic-film is OK to use. The ceramic-type is usually cheaper.

These small capacitors are usually rated for 25 or 50 volts. But even these versions may be a little small to deal with. If you're not used to handling small parts, you can get the 100-volt version of these small capacitors.

Small Capacitors
Ceramic typePlastic-film types

The Metric System

...is alive and well in the world of electronics. Resistor and capacitor values exist in very wide ranges. The metric SI prefixes are faithfully used. For resistors, the values in ohms can be large. The most common prefixes are "k" (kilo-, 1 thousand) and "M" (meg-, 1 million). For capacitors, the values in farads are very small. The most common prefixes are "p" (pico-, 1 trillionth), "n" (nano- , 1 billionth), and the small Greek letter Mu, μ (micro-, 1 millionth). Some places use "u" if "μ" isn't handy.

The Shopping List

Here is a link to my Beginner's Shopping List with links to the vendors with the best prices. Purchasing your parts online is the easiest way to start. Here's a run-down about the items on the list.

  • Solderless plug-in breadboard. The small size boards are sold on eBay for $1 to $2.
  • Wire jumpers for breadboard: color-coded solid 22- or 24-gauge, various lengths. You can make your own from pieces cut from a scrap telephone cable or Ethernet cable. (These are the cables that have multicolored solid-copper wires.)
  • Resistors, 1-watt, carbon-film or metal-film type: small assortment of values from 1 ohm (1 Ω) to 10 megohm (10 MΩ). Option 1: Get 1/2-watt (or even 1/4-watt) size resistors if you're OK with using very small parts. Option 2: Include extra quantities of 1 kilohm (1 kΩ), 10 kilohm (10 kΩ), 20 kΩ, and 100 kΩ.
  • Small Capacitors, ceramic or plastic-film type (non-polarized): small assortment of values from 1 nanofarad (1 nF) to 220 nF. Voltage rating: 50 volts is very common and a good choice, but 100-volt types are larger and a better choice if you're not used to handling small parts.
  • Large Capacitors, aluminum-electrolytic type (polarized): small assortment of values from 0.47 microfarad (0.47 μF) to 220 microfarads (220 μF). The very large ones – more than 220 microfarads – cost more money, so you might wait until you have project that needs them. Voltage rating: At least 16 volts. But 25, 35 and 50 volts are also very common and good to have, once you get more serious about electronics. The 50-volt types are larger and a better choice if you're not used to handling small parts.
  • Transistors, General purpose. Get 10 of each:
    • NPN-type: TN3019A or TN6719A are my large-size choices, but hard to find. Option: 2N3904 or PN3904 is smaller but very easy to find.
    • PNP-type: Either ZTX749A, TN6726A, or TN2907A — these are my large-size choices. Option: 2N3906 or PN3906 is smaller but very easy to find.
  • LEDs: any colors you like, like red, green, yellow, blue, white. (Red type is easiest for low-voltage circuits to drive.) They come in different sizes: 3mm, 5mm, 8mm, 10mm (mm = millimeter). Choose as big or small as you like. The 10mm size is big and chunky, while 5mm is most common.
    • For use as general indicator: LED with a diffused lens, and viewing angle around 60 degrees or more.
    • For use like a "flashlight"/narrow beam: LED with a clear lens, and viewing angle around 10 degrees.
  • Power source: Two (2) AA or AAA cells in a Battery Holder with wire leads.
    You could already have these at home, inside a flashlight or TV remove control. Alternatively, you could use an AC-DC adapter from a discarded cellphone if you know its output voltage and polarity — check it with a voltmeter. Don't use an adapter that supplies over 5 volts — it would damage these beginner circuits.
  • Miscellaneous:
    • Clip leads: flexible wire with alligator clips on each end.
    • Small speaker. Scavenge it from a discarded radio, intercom, or desktop PC.
      • And finally...
    • Parts organizer: to keep your parts from getting mixed up!

Buying everything on that list will cost around $50 (not including the taxes and shipping costs). If that's more than you want to spend, then here are some suggestions.

  • Leave off the parts organizer. That will cut the total cost in half. You can use paper envelopes to separately store each part, and store them in a shoebox.
  • Scrounge parts from old electronic gear. But it's not as easy now as it once was. Most of the parts in new equipment are tiny "chips" that are very difficult for hobbyists to use. Instead, you need to look for the "leaded" a.k.a. "through-hole" style of parts. Nowadays, these are mostly found in big things like power supplies and audio equipment. Or look for electronic equipment made before 1990 or so.
  • Start really small. In my next article, I'll present an even more basic kit of parts. Its cost is only about $5.

Pre-Packed Assortments of Parts

Hey! Some people (not me) have already done the work of making and selling a beginner's parts kit. Getting one of these may save you some time and mental energy.

  • Tinkersphere
    • Beginner's Electronics Kit with Breadboard — About $25. Has more parts than what an absolute beginner needs. And it requires a 9-volt battery, so you need to be more careful when constructing the circuits. Otherwise, a good choice, after you get familiar with building the basic circuits.

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