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Measuring Electricity
- Resistance – This is how we measure anything which holds back the flow of electricity between points in a circuit. Resistance is measured in ohms, and is most typically used when describing resistors.
- Voltage – The force with which electricity is being pushed through a circuit. Measured in Volts, and is typically used to describe power sources such as batteries and adapters.
- Conductance – The capacity for a conductor (like a wire) to allow electrons to flow through it. Measured in Siemens, As an example a piece of copper wire has a very high conductance while rubber has very very low conductance.
- Joule – The most basic measurement of energy, Joules can describe electrical energy but can also be used in relation to mechanical or thermal energy
- Power – How quickly electricity is used within a circuit, It refers to the rate at which joules are consumed over time and is measured in Watts
Components
- Resistor – Holds back or controls the flow of electricity through a circuit. Resistors will always have an associated ohm value which shows how much resistance they provide.
- Variable Resistors – Similar to resistors but with the ability to adjust the amount of resistance provided. The most common type of variable resistor found in electronic projects is the potentiometer which allows you to adjust the resistance manually using a knob or slider. Other types include photo-resistors which will vary their resistance based on light levels and thermistors which adjust the resistance based on temperature.
- Capacitor – A capacitor stores very small amounts of electricity temporarily. Capacitors fill a number of functions within circuits but are most commonly used to either store power or normalize voltage fluctuations. The capacitance of a capacitor is typically measured in micro-farads or nano-farads.
- Switches – Switches allow you to create a break in a circuit (effectively turning the circuit off) or select which route the electricity will take through a circuit.
- Diodes –Diodes will allow electricity to flow through them in one direction but will either resist or altogether stop the flow of electricity in the opposite direction.
Logic
- Logic Components – Specialized components which read digital inputs and output specific digital signals based on them. These include inverters, AND gates, OR gates, NAND gates and XOR gates. Note: digital signals have two states, 1 for on or 0 for off. Often these two positions are referred to as signal high (1) and signal low (0)
- Truth Table – A truth table can be a useful tool when dealing with logic chips, a truth table is essentially a grid showing possible input values and the resulting outputs for a logic circuit. A Truth table for an AND Gate would look something like this:
| Input 1 |
Input 2 |
Output |
| 0 |
0 |
0 |
| 1 |
0 |
0 |
| 0 |
1 |
0 |
| 1 |
1 |
1 |
- Inverter – An inverter is a digital logic component which outputs the opposite state of whatever signal is inputted into it. For instance if the input is high, the output will be low.
- AND Gate – A logic gate with two inputs and one output. If both inputs are high the output will also be high. If only one or none of the inputs are high than the output will be low.
- OR Gate – An or gate also has two inputs and one output. On an OR gate if either input is high the output will be high. If both inputs are high the output will also be high.
- NAND Gate – A NAND gate will output a high signal if neither or one of the inputs is high but will switch to outputing a low signal if both inputs are high.
- XOR Gate – An XOR gate (Exclusive Or Gate) is similar to an OR Gate with the crucial difference that if both inputs are high the output will be low.