An overview of basic electronic components.
{Note: a wire will impede the flow of electricity, but it is so slight that we can usually ignore its effects.}
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.
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.
Some common types are:
Some common types of power supplies:
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].
Some common types of Diodes:
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.
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).
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.
Two common types of transistors are:
{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.
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.
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