Learning electronics tutorials for beginners is the primary goal of this site.
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Keep in mind that incandescent light bulbs are really rare now (replaced with LEDs). They are however a simple component to understand.
Electronics involves combining components together to form circuits that do something useful. All circuits generally contain at least…
- Power source – Provides voltage and current to a load.
- Load – Does something useful with the voltage and current (power) from the power source.
- Connectors – Provide an electrically conductive path from the power supply, to the load, and back to the power supply.
- Conductor – Passes current easily.
- Insulator – Doesn’t pass current easily. Typically used to keep conductors separated.
I really like the kit above for learning basic electronics and Arduino. This is an affiliate link ad, so I earn from qualifying purchases, which helps me devote time to improving this site.
When current flows through a light bulb, it’s filament heats up and it emits light.
More voltage means more current, and thus more heat for a resistive component such as a light bulb. Therefore don’t exceed the light bulb’s rated voltage or it will get too hot. This is known as wattage and heat dissipation which is covered later.
Any direct current (DC) voltage source of the proper voltage and polarity can be used to provide power to a DC load regardless of the power source symbol shown in the schematic.
Power supply used in my videos. Affiliate link ad.
LED protected by a resistor:
Much more common these days than incandescent light bulbs are LEDs that are protected from a power source with a resistor.
Good minimum value resistors to use for a given voltage source…
- 5V – 220Ω
- 9V – 470Ω
- 12V – 1000Ω (1k)
- Protective resistor must have high enough resistance to limit current below 20mA for most LEDs. It’s resistance must also be high enough that it doesn’t get too hot (wattage) for the voltage being applied.
Most resistors are rated to dissipate a maximum of 1/4W (0.25W) of power. It is still recommended to stay below 1/8W (0.125W). Other wattages are easy to obtain. Covered in more detail below.
Batteries are a cheaper and more portable voltage source than a plug in power supply. However, they need to either be replaced often, or recharged if rechargeable.
A cell contains the chemistry needed to provide a voltage. The nominal voltage will depend on the chemistry involved.
Nominal voltage is close to the average voltage that you can expect when a cell goes from fully charged (highest voltage possible) to fully discharged (lowest practical voltage).
- Alkaline has a nominal cell voltage of 1.5V. The actual voltage ends up being 1.6V while brand new (they aren’t usually rechargeable), and somewhere close to 1V when fully discharged.
- Lithium ion (li ion) cells usually have a nominal voltage of 3.6V, which ends up being 4.2V when fully charged and 3V when fully discharged. Stay within that voltage range to prevent dangerous damage.
- Series cells: Cells must be at the same voltage and capacity (mAh) Connecting cells end to end (positive of one cell to negative of another cell) adds up the voltage of each cell when taken from the 2 far ends.
- Parallel cells: Cells must be at the same voltage. Connecting the positive end of each cell to the positive of the others, as well as connecting the negatives ends together, provides the same voltage as one cell, but adds up how much total current can be provided to a load. Make sure the batteries are at the same voltage (no more than about 0.1V difference) before connecting in parallel.
Battery holders that connect the cells in series or parallel for you when you insert them in the proper direction are common.
A 9V alkaline battery has the chemistry of six 1.5V cells contained in one package.
“9 volt” lithium ion rechargeable batteries can only be charged to 8.4V because they are made up of two 3.6V cells (4.2V cells when fully charged). I prefer to call them almost 9V batteries.
Always use a proper battery charger for the chemistry involved, unless you have learned how to charge that chemistry safely.
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- LED must be inserted in the right direction to light up (forward biased). That is when the Anode (longer lead) is more positive, and the Cathode (shorter lead) is more negative. That assumes that the Anode lead has not been trimmed. Leads (pronounced as “leeds”) are the metal wires coming out of through hole components. Many LEDs also have a flat edge on the cathode side.
Other types of diodes have a band painted on the cathode side of the component.
- Schematic diagrams are drawings of circuits where symbols are used to identify components and their connections, instead of using drawings or pictures of actual components.
(protective) resistor setting current
Resistors set current through them (and series components) based on the voltage across them and their resistance. Current (in Amps – I) through a resistance is the voltage (in volts – V) across the resistance divided by the resistance (in ohms – Ω). That is the Ohms law formula I = V/R .
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- 1V/1,000Ω = 0.001A (1mA – one milliamp)
- 10V/1,000Ω = 0.01A (10mA – ten milliamps)
A resistor heats up when it passes current. They are rated for wattage instead of current. Larger resistors can dissipate heat better, and thus have a higher wattage rating than smaller resistors. W=IV
- 1V/0.001A = 0.001W
- 10V/0.01A = 0.1W
When you buy resistors, they generally all come in the same size (wattage) even though they have different resistance values.
Most commonly sold are 1/4 watt resistors. Therefore it is generally assumed that you are using 1/4W resistors unless another wattage resistor is indicated.
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- 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.
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