Components

An overview of basic electronic components.

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Wire

A Wire is one of the most basic, and crucial components available. A wire allows for the unimpeded flow of electricity. A wire is used to connect the components of a circuit together. A wire can be thought of as any device that is intended to route electricity from one component to another. In this sense a wire can be the traditional metal core, insulator wrapped wire. Additionally it can also be the trace on a circuit board or the solder connection between two components in the absense of a "traditional" wire.

{Note: a wire will impede the flow of electricity, but it is so slight that we can usually ignore its effects.}

Physical Wire

Physical wire (as opposed to pcb traces, or wires on schematics) can be divided into two general categories: solid, and stranded. The difference is how easily the wire bends, and how easily it breaks. All wires that need to flex, such as the line cords on appliances or wires to your audio speakers should be stranded wire. Solid wire is used where the wire doesn't need to flex and where having one solid conductor makes the wire easier to work with.

Examples of places where solid wire is used are inside the walls of buildings and on electronic breadboards. In both cases, the wire won't be doing a lot of flexing, and is easier to use as one solid conductor, rather than lots of smaller strands.

Wire Gauges

Breadboards are generally designed to use 22 gauge wire, although they can accommodate a gauge or two either way. Arduino female headers are not designed for inserting wire, but it works well enough for many prototype situations. 20 gauge is probably more dependendable in Arduino headers than 22 gauge but both will work. In wire gauges, larger numbers correspond with smaller wire.

Radio Shack, although one always hesitates to recommend them, sells solid and stranded wire. Look for 22 gauge solid (or alternately 20 gauge solid) wire for use with your 'duino and a breadboard.

If you need a fair quantity of breadboard wire you can obtain it inexpensively, and in several colors, by buying solid conductor telephone cable. Make sure it's solid conductor though as both solid and stranded are sold. You can find this at home improvement stores and at R.S. This is commonly 24 gauge, so is one size smaller than ideal, and can be doubled back on itself to make secure connections in 'duino female headers.

Old computer cables contain a wealth of stranded wire in various gauges and colors that is extremely useful for wiring small electronic projects. Obtain them wherever tech trash is discarded.

Breadboard

A Breadboard is a device that facilitates the construction and testing of circuits. Typically they are used for prototyping circuit designs.

Some common types are:

  • Solderless Breadboard - has a plastic faceplate with holes that the components can be inserted into. The components make electrical contact to metal strips underneath the faceplate. In this way no solder is needed to hold the components in place.

Power Supply

A Power Supply is a device that provides a source of electric power for a circuit. A power supply creates a voltage across its output pins. The measure of voltage and current that is supplied varies between devices.

Some common types of power supplies:

  • Benchtop Power Supply - provides power from an AC (alternating current) source to DC (direct current).
  • Battery - A self contained device that produces power by chemical reactions in the battery. Properties of these reactions are known and therefore the voltage and current are known.
  • "Wall Wart" - typically a small device that plugs into an outlet and converts AC to DC at a predetermined voltage and current.
  • Solar Cell - converts light to electrical voltage and current. These may vary based on the intensity of the light.

Resistor

A Resistor is a device that resists the flow of electricity. This resistance to the flow of electricity can be used to limit the amount of current flowing into an electrical component. Their ability to resist current is measured in Ohms [R] or [Capital Omega].

Capacitor

A Capacitor is a device that can store and release electrical charge in a circuit. Typically a capacitor consists of two charging plates with a material in between that prevents electrical discharge. Although other types of capacitors can be produced. These devices can be used to smooth out signals in a circuit. Additionally, large capacitors can be used as storage systems for current. Their ability to store charge is measured in Farads [F].

Inductor

An Inductor is a device that stores electrical energy in a magnetic field. An inductor is a coil of wire. When a current is sent down the wire a magnetic field is generated. When the flow increases, more energy is stored in the magnetic field; when the flow decreases, the energy is released as electrical power. An inductor can be used to smooth or filter out variations in current, much in the same way a capacitor can. The ability of an inductor to store electrical energy is measured in Henrys [H].

Diode

A Diode is a device that only allows for the flow of electricity to pass in one direction. These components are often used to isolate the effect of one component from another.

Some common types of Diodes:

  • Light Emitting diode (LED)
  • Photo diode - detects light
  • Laser diode - emits a coherent light beam (laser)
  • Zener diode - prevents current flow up to a voltage threshold.

LED

A LED is a diode that generates a specific wavelength of light when a voltage is applied across its leads. This voltage is known as the forward voltage of the LED. The brightness of the light varies as the current is varied.

An LED has no inherent current limiting, so applying voltages higher than the forward voltage will usually result in overheating or burning out the LED. Often the LED is damaged by this and will still light up, but never be as bright as its original specification.

Current-limiting series resistors

The simplest way to limit current to an LED is to use a resistor in series with the LED. To calculate the proper value of resistor, it is easier to use Ohm's Law to calculate the electrical current through the resistor, and not the LED. This works out well because the current through a series circuit is the same at every point in a circuit, meaning the current will be the same through the LED as the current through the resistor.

Here's an example: An LED is going to be powered from a 5 volt supply. Checking the LED's datasheet, the forward voltage is 3 volts. So a resistor in series with the LED would have 5 volts - 3 volts = 2 volts across the resistor.

To put 20 milliamps through the LED (a typical specification for a brightly lit LED), Ohm's law would look like this.

E = IR

E = voltage in volts I = current in amps R = resistance in ohms

2 volts / .02 amps = 100 ohms, so using a 100 ohm resistor in series with the LED will light it at a current of .02 amps (20 milliamps).

So can I plug an LED into a 'duino without a resistor?

The answer is yes, although this is not necessarily the best of techniques. An Atmega pin can only supply about 40 milliamps which is not enough current to damage stndard LED's. A better choice would be a series resistor with a value of between 100 ohms and 1k, connected between the LED and ground.

Pushbutton

A Pushbutton is a device that either completes or interrupts the flow of electricy in a circuit due to force on the button. Pushbuttons come in many configurations and types. A common type is the momentary switch. When a force is applied to the button the button will either complete the connection (this is known as a normally open switch) or will interrupt the connection (this is known as a normally closed switch). These devices can be useful for interrupting signals to the microcontroller (arduino) for input.

Transistor

A Transistor is a device that restricts or allows the flow of current between two contacts based on the presence or absence of current on a third contact. A transistor has three leads: collector, emitter and base. The collector and emitter act as the input and output for the transistor. While the base is the trigger for the signal.

Two common types of transistors are:

  • PNP - If the base voltage is less than the emitter voltage, then current flows from the emitter to the collector.
  • NPN - If the base voltage is greater than the emitter voltage, then current flows from the collector to the emitter.

{Note: The P stands for P-type semiconductor and the N stands for N-type semiconductor}

Two common uses for transistors are to act as an electrically activated switch. Also transistors can be used to increase (amplify) the output current.

Relay

A Relay is a device that completes a connection between two contact points by means of a mechanical movement. A relay may use a solenoid to magnetically move a contact switch. A signal is sent to the relay which can be used as the source of the electromagnet. They are typically used as switching mechanisms allowing for small DC current to switch large AC or DC currents. In this application they can isolate the more sensitive control circuitry from the larger components.

Photoresistor

A photoresistor is a special type of resistor that is photo (or light) sensitive i.e. the resistance changes according to how much light is on the photoresistor

Actuator

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