Learning electronics tutorials for beginners is the primary goal of this site.
Introduction to electronics
- Voltage = Electrical pressure. The force needed to move electric current. One side is more positive and the other side is more negative. Those 2 points have a voltage diffence. A 9 volt alkaline battery has about a 9 volt (depends on how charged it is) difference between it’s positive and negative terminal. Negative terminal is typically called the 0V reference point or ground. While a 9V battery’s positive terminal is considered to be at 9 volts. So there’s a 9V difference between 0 and 9V. -Unit: Volts -Symbol: V
- Current = Moving charges. Traditionally imagined as being a positively charged fluid going from more + to more -, and called conventional current. We still talk about current through a circuit in this way. Electron flow is what actually moves through a circuit. Electrons flow from more negative to more positive, and when studying what electricity is actually doing at an atomic level, you must use electron flow. -Unit: Amperage (Amp) -Symbol: A or I. Remember that a capital i looks like a lowercase L in many fonts.
- Resistance = The opposition to current flow. Resistive components allow a certain about of current through them, based on their resistance and the voltage across them – I = V/R. This mathematical relationship is called Ohms law. -Unit: Ohms -Symbol: Ω (greek letter omega) or R
Studying electronics involves learning about circuits. Circuits are made up of one or more components, power source(s), and connectors, that have particular electrical, and other, properties.
- Light bulbs generate heat from the electrical current flowing through them. That heat emits light. Voltage must be limited to their rated value.
- LEDs emit photons more directly from the current flowing through them. A proper resistor must be used based on the voltage to protect the LED. LEDs are more efficient than light bulbs, and more commonly used now.
In video below:
- Breadboard with 5V applied at the power rails.
- Normally open (NO) push button switch: It is off until you press it.
- LED: current must be limited to 20mA or less.
- Resistor: For 5V, the 220Ω resistor in series with LED limits current to less than 20mA and keeps the resistor heat generation under 1/8W, which is recommended for the commonly used 1/4W resistor. for 9V supply I use at least 470Ω and for 12V supply I use at least a 1,000Ω (1kΩ) resistor.
Batteries can be used to power the breadboard. They need a holder for cylindrical batteries, or a snap for the 9V version. The wires from the holder/snap can be plugged into the supply rails. If the wires are stranded (a lot of thin wires) then they will need to be twisted together first.
Using LEDs to “see” polarity
Since LEDs only light up in one direction (forward biased), they can be wired in parallel but in opposite directions of each other and then in series resistor. Applying a voltage in either direction will light up the forward biased LED only.
More in depth material
Diagram used in that video is at 001 Resistive component multimeter voltage-current-resistance measurements
Resistor limiting current
LEDs need to have current limited through them or they will burn out. Usually the current should be limited to no more than 0.02A (20mA). The resistor is typically used to set the current through the LED or other components that need protection.
- Ohms law for current: I=V/R
- Ohms/power law for power (heat generated) by a component from a voltage and current: P=VI
One of the versions of the Ohms law formula (I = V/R ) explains what the current through a particular resistor will be based on the voltage across it. Current (I) equals voltage (V) across a resistor divided by the resistance of the resistor (R).
The (power) heat generated by the resistor is the voltage across the resistor times the current flowing through it (P=VI) and is given in units called watts (W). The typically resistor is usually rated for 1/4W (0.250W). That will make the resistor really hot though, and so it is recommended to always keep the wattage below half of the rated value as much as possible.
LED voltage drop
The LED, and other diodes, help the resistor limit current by reducing (dropping) some of the supply voltage from going across the resistor. Series (connected end to end electrically) components always split up/divide the supply voltage among them based on their voltage drop or their percentage of the total resistance after voltage drop are taken into account.
- Information on this site is not guaranteed to be accurate. Always consult the manufacturer info/datasheet of parts you use. Research the proper safety precautions for everything you do.