Electronics


http://www.tigoe.net/pcomp/index.shtml - You can't do much better than to look at the collection of resources, examples, and lecture notes for the physical computing courses at ITP.

A (very brief) overview of some of the basic components and tools that we will most commonly be using. This is by no means exhaustive.


Wire

A wire is a single, usually cylindrical, elongated string of metal. Wire is used to carry an electrical current. Most wire is protected by an insulating covering of plastic. Solid wire, also called solid-core or single-strand wire, consists of one piece of metal wire. Stranded wire is composed of a bundle of small-gauge wires to make a larger conductor. Stranded wire is more flexible than solid wire of the same total cross-sectional area. Solid wire is cheaper to manufacture than stranded wire and is used where there is little need for flexibility in the wire. 22 American Wire Gauge (AWG) solid-core hook-up wire is best for making solderless breadboard connections. Get at least 3 colors, and always use red for voltage and black for ground.

Jumper wires can be purchased pre-cut from electronic retailers. You can make your own jumper wires of any length by cutting the required length from a spool of wire and stripping off the plastic insulation with wire strippers.

Alligator Clips (on jumper wire)

 
An alligator clip (or spring clip) is a temporary electrical connector, named for its resemblance to an alligator's jaws. Functioning much like a spring-loaded clothespin, the clip's two tapered, serrated jaws are forced together by a spring to make contact with a wire or other component. Alligator clips can also be used as miniature clamps to hold parts together for gluing and wires together for soldering.

Clip Leads (on jumper wire)

 
Small test leads with miniature spring-loaded hooks at both ends. Ideal for temporary, hard-to-get-at circuits. These are not as robust at alligator clips and may need constant resoldering.

Wire Stripper

A wire stripper is a small, hand-held device used to strip the insulation from electric wires. has several notches of varying size. This allows the user to match the notch size to the wire size. Once the device is clamped on, the remainder of the wire can simply be pulled out, leaving the insulation behind.

Pliers

Pliers are a type of hand tool used to hold objects firmly, or for cutting and bending tough materials such as wire. Generally, pliers consist of a pair of metal levers joined at a pivot positioned closer to one end of the levers, creating short jaws on one side of the pivot, and longer handles on the other side. This arrangement allows the power of the hand's grip to be amplified and focused on the object with precision. The jaws can also be used to manipulate objects too small or unwieldy to be manipulated with the fingers.

Switches

Mechanical switches permit or interrupt the flow of current. They are also used to direct current to various points.


Resistors

 
A resistor is a component of an electrical circuit that resists the flow of electrical current. A resistor has two terminals across which electricity must pass, and is designed to drop the voltage of the current as it flows from one terminal to the next. A resistor is primarily used to create and maintain a known safe current within an electrical component. Resistance is measured in ohms (Ω), after Ohm's law (V=IR). This rule states that the voltage (V) across a resistor is proportional to the current (I) through it where the constant of proportionality is the resistance (R). A high ohm rating indicates a high resistance to current. Resistors use a pattern of colored stripes to indicate resistance. Four-band identification is the most commonly used color-coding scheme on all resistors. It consists of four colored bands that are painted around the body of the resistor. The first two bands encode the first two significant digits of the resistance value, the third is a power-of-ten multiplier or number-of-zeroes, and the fourth is the tolerance accuracy, or acceptable error, of the value.
 
A decent explanation of how to read these color codes is here http://www.bcdxc.org/resistor_color_codes.htm download the attached pdf (at the bottom of this page) or you can use one of many online calculators, such as:
http://www.electronics2000.co.uk/calc/resistor-code-calculator.php there are free iPhone and Android apps available (e.g. ResistorCode by Christopher Brown, eTools).
http://myresistor.com/

Capacitors

 
There are many kinds of capacitors, but they all do the same thing: store electrons. The simplest capacitor is two conductors separated by an insulating material called the dielectric. When a voltage potential difference exists between the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the plates. The effect is greatest between wide, flat, parallel, narrowly separated conductors. Values of capacitors are usually specified in ranges of Farads (F), microfarads (μF or MFD), nanofarads (nF), or picofarads (pF), as one, millionths, billionths or trillionths of a farad. Capacitors can store a charge for a considerable time after the power to them has been switched off. This charge can be dangerous.

Diodes

 
The most common function of a diode is to allow an electric current in one direction (called the forward biased condition) and to block the current in the opposite direction (the reverse biased condition). Thus, the diode can be thought of as an electronic version of a check valve.

Transistors

 
In electronics, a transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much larger than the controlling (input) power, the transistor provides amplification of a signal.

LEDs

 
A light-emitting diode (LED) is an electronic light source.  It is easy to figure out which side of an LED is positive and which one is negative. The positive leg is slightly longer and if you look inside, the chunk of metal is larger on the negative side. Too much current will overheat an LED and possibly separate the leads. LEDs should be used with a current-limiting resistor in series with the LED.
 
LED calculator: current limiting resistor value http://www.superbrightleds.com/led_info.htm
LED series/parallel array wizard is here http://led.linear1.org/led.wiz
Also useful http://www.ohmslawcalculator.com/led_resistor_calculator.php enter any three known values and press "Calculate" to solve for the others.

 
If you can afford to pay more there are also high-power LEDs, networkable and programmable full-color RGB LEDs, too.

Potentiometers

 
A potentiometer (pot) is a three-terminal resistor with a sliding contact that forms an adjustable voltage divider. Potentiometers are used to adjust the level of analog signals (e.g. volume controls on a radio or a dimmer on a lamp), and as control inputs for electronic circuits. Potentiometers are sometimes provided with one or more switches mounted on the same shaft. For instance, when attached to a volume control, the knob can also function as an on/off switch at the lowest volume.

Breakable Header Strips

 
These 0.1" header strips are commonly used as low-cost connectors. The standard spacing allows use with solderless breadboards, perforated prototyping circuit boards and female headers. These header strips can easily be snapped into smaller strips to fit your application.

Solderless Breadboards

 
A solderless breadboard is a reusable device used to build a temporary prototype of an electronic circuit and for experimenting with circuit designs. Various sizes and colors are available. Often breadboards of the same brand can be clipped together to make a larger breadboard (not with mini breadboards). Breadboards consist of a perforated block of plastic with numerous tin plated phosphor bronze or nickel silver alloy spring clips under each row of 5 perforations. The spacing between the clips is typically 0.1" (2.54 mm). Wires and the leads of discrete components (such as capacitors, resistors, etc.) can be inserted into the clips through the perforations to complete a circuit. In the middle of a terminal strip of a breadboard, one typically finds a notch running in parallel to the long side. The notch is to mark the centerline of the terminal strip and provides limited airflow (cooling) to dual in-line package (DIP) integrated circuits (ICs) straddling the centerline. Breadboards usually have a bus strip containing two columns, one for ground, one for a supply voltage along their edges (not with mini breadboards). Most breadboards are backed with double-sided adhesive. This is useful until you decide to reuse the breadboard elsewhere. This can result in pulling the clips from the plastic block. High-end versions of solderless breadboards exist. These typically contain additional components such as power supplies, signal generators, serial interfaces, LED or LCD display modules, logic probes, etc.

Protoboards

 
Protoboards, stripboards, Veroboards or perfboards are a more permanent (less-temporary) type of electronics prototyping board than a solderless breadboard. Various kinds are available in many shapes and sizes but most feature a 0.1 inch (2.54 mm) regular (rectangular) grid of holes. The components are usually placed on the plain side of the board, with their leads protruding through the holes. The leads are then soldered on the other side of the board to make the desired connections, and any excess wire is cut off.

Handheld Multimeters

 
 
A handheld multimeter is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter may include features such as the ability to measure voltage, current and resistance. There are two categories of multimeters, analog multimeters and digital. A multimeter can be used to troubleshoot electrical problems in a wide array of industrial and household devices such as batteries, motor controls, appliances, power supplies, and wiring systems. Multimeters are available in a wide ranges of features and prices.

Variable Bench Top Power Supplies

 
A variable bench top power supply is a device that allows you to change the voltage and current of an electrical supply to suit a particular application. This is particularly handy when testing motors. Please be careful.

AC Adapters (wall warts)

 
A power supply or transformer that has a mains electrical plug built in. The example pictured above is thinner than is usual - this can be useful when you want to run multiple devices on a single power strip (see below).

Batteries

 
 
 
A battery is a device that converts chemical energy directly to electrical energy. A battery pack is a set of any number of (preferably) identical batteries or individual battery cells. They may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power density.

Power Strips

 
A power strip is a series of electrical sockets that attaches to the end of a flexible cable and allows multiple devices to be plugged in to a single power outlet. If you want to run multiple devices on a single power strip, the orientation of the sockets can limit the number of AC Adapters you can plug in. The example pictured above can accommodate 6 of the thinner-type of wall warts (see above). This is not the case with all power strips.

Solar Cells

 
A solar cell or photovoltaic cell is a device that converts light directly into electricity by the photovoltaic (PV) effect. The photovoltaic effect involves the creation of a voltage (or a corresponding electric current) in a material upon exposure to electromagnetic radiation. In most photovoltaic applications the radiation is sunlight and for this reason the devices making use of the photovoltaic effect to convert solar energy into electrical energy are know as solar cells. Assemblies of cells are used to make solar panels, solar modules, or photovoltaic arrays. Solar cells are often electrically connected and encapsulated as a module. PV modules often have a sheet of glass on the front (sun up) side, allowing light to pass while protecting the semiconductor wafers from bad weather and bird shit.

Soldering Irons

 
 
A soldering iron is a tool used for applying heat to two adjoining metal parts such that solder may melt and flow between those parts. A soldering iron is composed of a heated metal tip and an insulated handle. Heating is often achieved electrically, by passing a current, supplied through an electrical cord or a battery, through a heating element. A soldering iron stand keeps the iron away from flammable materials, and often also comes with a sponge and flux pot for cleaning the tip. Some soldering irons for continuous and professional use come as part of a soldering station, which allows the exact temperature of the tip to be adjusted, kept constant, and displayed.

Solders

 
Solder is a fusible metal alloy that is melted to join metallic surfaces together. Solder is often manufactured as a hollow tube and filled with flux. Flux is a chemical cleaning agent which facilitates soldering by removing oxidation from the metals to be joined.

Solder can contain Lead. The Restriction of Hazardous Substances Directive (RoHS) took effect on 1 July 2006, in the European Union. This directive restricts the use of six hazardous materials in the manufacture of various types of electronic and electrical equipment (Lead, Mercury, Cadmium, Hexavalent Chromium, Polybrominated Biphenyls, Polybrominated Diphenyl Ether). RoHS is part of a legislative initiative to solve the problem of huge amounts of toxic e-waste. When selecting components look for the "RoHS compliant" label.

Desoldering Pumps

 
A desoldering pump or "solder sucker" is a spring-loaded device which is used to remove solder from a printed circuit board (PCB). It is applied to a heated solder connection, then the user activates the device (usually by pressing a button) to "suck" the solder away.

Helping Hands

 
Helping hands usually have dual alligator clips to hold work in any position. Can hold items (sort of) securely, leaving hands free for soldering. Built-in magnifying glass can help with detail work (when its not in the way).

Connectors

 
 
Some connector styles may contain plugs (male), sockets (female) or both connection types. A socket is better described as a receptacle that is designed to be fixed on the surface of an enclosure. Its counterpart, the plug, is designed to attach to a wire, cable or removable electrical assembly.

Heat Shrink Tubes

 
Heat shrink is a plastic tube that shrinks in diameter when heated. Its diameter and thickness can vary, and there are three main categories: thin-wall, medium-wall and thick-wall. Heat shrink is used to insulate, repair, bundle and protect wires and small parts.

Adhesive Tapes

 
Electrical tape is a type of pressure-sensitive tape used to insulate electrical wires and other materials that conduct electricity. It can be made of many plastics, but vinyl is most popular; it stretches well and gives an effective and long lasting insulation. Duct tape is a vinyl, fabric-reinforced, multipurpose pressure-sensitive tape with a soft and tacky adhesive. Gaffer tape (not pictured) looks like duct tape but does not leave a sticky residue when removed and is more easily torn into thin strips for precise application. Double-sided tape is coated with adhesive on both sides. It is designed to stick two lightweight surfaces together. Masking tape is made of a thin and easy-to-tear paper, and an easily-released pressure sensitive adhesive. There are many other varieties of tape. Please note: unbranded, cheap tape costs less for a reason.

Glues

 
Glue is a compound in a liquid or semi-liquid state that adheres or bonds items together.

http://www.adhesives.org/

http://www.thistothat.com/ - a recommendation from Eric Harman.

Grip Pads

 
Adhesive-backed, rubber bumpers that can help protect a circuit board and keep it from sliding around.

Screwdrivers

 
A device specifically designed for the insertion and tightening of screws. The screwdriver is made up of a head or tip, which engages with a screw, a mechanism to apply torque by rotating the tip, and some way to position and support the screwdriver. A typical hand screwdriver comprises an approximately cylindrical handle of a size and shape to be held by a human hand, and an axial shaft fixed to the handle, the tip of which is shaped to fit a particular type of screw. The handle and shaft allow the screwdriver to be positioned and supported and, when rotated, to apply torque. Screwdrivers are made in a variety of shapes, and the tip can be rotated manually or by an electric motor.

Hardware

 
 
The parts and fittings that are used to make your projects stronger, more functional, longer lasting and easier to fabricate and assemble.

http://www.grainger.com/
http://www.mcmaster.com/
http://www.smallparts.com/

USB Cables

 
Universal Serial Bus (USB) is a serial bus standard to connect devices to a host computer. USB was designed to allow many peripherals to be connected using a single standardized interface socket and to improve plug and play capabilities by allowing hot swapping; that is, by allowing devices to be connected and disconnected without rebooting the computer or turning off the device. Other convenient features include providing power to low-consumption devices, eliminating the need for an external power supply; and allowing many devices to be used without requiring manufacturer-specific device drivers to be installed.

Project Enclosures, Mint Tins, Boxes...

 
 
Somewhere to put your electronics. Most commercial enclosures feature standoffs in the bottom corners to support a circuit board.

http://www.polycase.com/ - One of many companies that sell project enclosures.
http://www.otterbox.com/search/1000/otterbox-1000/ - Need waterproof? Try this.
http://science.howstuffworks.com/tinnovation-microsite.htm - How many different purposes can an mint tin serve?
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John Marshall,
Jun 11, 2009, 7:38 PM
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