We assume all of us have already learned some basic electronic. At least, you need to understand basic circuit and circuit diagrams. Below are some simple facts:
Structure of matter All matter is composed of molecule. A molecule is a group of atoms bunched together.
Structure of an atom Atoms are composed of protons, neutrons, and electrons. The forces of attraction between the electrons and the protons hold an atom together.
Electrons Electrons have a negative electrostatic charge and protons have a positive electrostatic charge. Like charges repel, unlike charges attract, just like with magnets. Atoms have their electrons arranged in layers called shells. In order to maintain electrical balance the number of electrons is equal to the number of protons in most elements.
Electricity The valence shell is the outer shell of the atom. Some materials have a free electron in their valence shell and this electron can easily move from atom to atom. The free electrons are responsible for electrical current. Electricity is a word used to describe the directional flow of electrons between atoms.
Current (I) The directional movement of electrons between atoms is called electrical current. Amperage is a term used to describe the number of electrons moving past a fixed point in a conductor in one second. Current is measured in units called amperes or amps. Consider current as the volume of water passing though a section of water pipe at specific time.
EMF (V) EMF is electromotive force. EMF causes the electrons to move in a particular direction. EMF is measured in units called volts. Consider voltage as the speed of water flowing through the water pipe.
Resistance (R) Resistance is the opposition to electrical current. Resistance is measured in units called ohms. Resistance is sometimes desirable and sometimes undesirable. Consider resistance as the friction/blocking of dirts in a water pipe.
Conductors and insulators Conductors conduct electrical current very easily because of their free electrons. (e.g. copper, aluminum, gold) Insulators oppose electrical current and make poor conductors. (e.g.glass, air, plastic, rubber)
Ohm’s Law Ohm’s Law is used to describe the mathematical relationship between voltage, current, and resistance.
V = I x R
Power (P) Power refers to the amount of energy convert from one form to another in a certain period of time. In terms of electricity, it means the amount of electrical energy being converted to other forms of energy such as sound, heat or kinetic energy. Remember! Always avoid short circuit (circuit without resistance, otherwise we will have very large current and power, which is very dangerous and may burn components and cause fire.
P = IV
Energy (E) When measuring energy, we use the unit “Joules”. Electricity energy is measured by the following equation (t is time)
E = Pt = IVt
Circuit Wires and various components connected together form a circuit. A load is any device in a circuit that is using the energy that the electron current is delivering to it. Circuit diagrams are used to show how all the components connect together to make a circuit.
When all the components are in line with each other and the wires, a series circuit is formed.
When some of the components are connected parallel with each other, they form a parallel circuit.
A voltmeter must be wired in parallel in a circuit in order to measure the difference in EMF from one point to another.
DC and AC
DC, or direct current means the electrical current is flowing in only one direction in a circuit.
Batteries are a good source of direct current (DC).
AC, or alternating current means the electrical current is alternating directions in a repetitive pattern.
AC is created by generators in power plants, and other sources. This AC current is delivered to our homes and businesses by the power lines we see everywhere.
Inform your teacher or school staff immediately when you become aware of a safety hazard.
• In this workshop only DC is used. Do not use AC in any case.
• Do not work on a live circuit unless ABSOLUTELY NECESSARY and under supervision of tutor/lecturer.
• Stand on dry, non-conductive surfaces when working on live circuits.
• Always keep your hands dry.
• Maximum voltage used inside the workshop is 9V, and only battery can be used (no AC adepter).
• Any current flow above 0.005A/5mA is considered dangerous
• A common 1.5V dry cell could output as much as 2.5A ==> strong enough to kill a person!
• Never take a shock on purpose.
No soldering is allowed in the classroom.
Our workshop only focus on software developing on microcontroller, but not building electronic products. You can do your soldering for your projects (if necessary) outside the class.