Power is the amount of work being done. The unit used for power is called the watt. Some forms of power in electronics include an LED lighting up, motors spinning, and when things heats up as current is forced through them.
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- Watt: A unit of power – Rate of energy transfer
- P = VI – Power (P) in watts (W) equals the voltage in volts (V) times the current (I) in Amps (A)
- 1W = 1 joule per second = 1V times 1A
Heat is just wasted power unless your goal is to heat something. Heat is also what damages electric components. Therefore, it is important that you keep the power consumption of all components below half of their maximum wattage rating.
Keep in mind that you may only get a maximum and/or recommended current rating for some components instead of a wattage rating.
Series components split up the voltage across them and therefore also split up the power dissipation.
Diagrams of common values:
Most resistors are rated for a maximum of 1/4W (0.25W), and should ideally be kept below 1/8W (0.125W) to ensure a long life.
This diagram shows the current and wattage for a 100Ω and a 1,000Ω resistor with different voltages across them. The highest voltage next to each of them is close to the maximum voltage you would want to put across them.
- 3.3V across 100Ω – 3.3V/100Ω = 0.033A (33mA) through the resistor | 0.033A x 3.3V = 0.1089W heat generation.
- 5V across 220Ω | 5V/220Ω = 0.0227A (23mA) through the resistor | 0.023A x 5V = 0.115W heat generation
- 9V across 1KΩ | 9V/1000Ω = 0.009A (9mA) through the resistor| 0.009A x 9V = 0.081W heat generation.
Resistors with the added protection of an LED voltage drop.
Below are resistor values and supply voltages that are slightly higher than the desired 1/8W (0.125W) of a 1/4W (0.25W) resistor alone. But, by adding a series LED, there is enough of the voltage dropped to make it safe for the resistor.
Forward biased LEDs typically have a forward voltage of about 2-3 volts; which is dropped from series components.
Commonly available values being given. Numbers are rounded off. Higher value resistors are even safer to use.
- 9V: 2V LED drop = 7V across resistor – 470Ω/7V = 0.0149A (15mA) through resistor and LED – 0.015A x 7V = 0.105W heat generated by resistor.
- 12V: 2V LED drop = 10V across resistor – 10V/1000Ω = 0.01A (10mA) through resistor and LED – 0.01A x 10V = 0.1W heat generated by resistor.
Bonus video and diagram:
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Other basic electronics topics that you should know before moving on to more advanced topics.
- Electronic component appearance and schematics – Commonly used through hole versions
- Electronic circuit basics
- Voltage sources for electronics basics
- Multimeter measuring voltage
- Resistor component – Learning electronics resistors
- Light Emitting Diodes – Indicator LEDs
- LED circuit -Lighting a Light Emitting Diode
- Resistor limiting current – Ohms law
- Multimeter measuring current
- Wattage – Electrical Power unit
- Resistors connected in parallel
- Series resistors
- Voltage divider – Setting a fractional voltage
- Resistor color code
- Diode – Rectifier
- Trimpot – Trimmer potentiometer – Voltage divider – Variable resistor
- Capacitor component
- Capacitor RC time constant
- Voltage ramp Demonstrated using a capacitor.
- LM334 three terminal adjustable current source not a common component. I use for an easy current source in many circuits.
- Switch NOT logic gate – digital signal inverter
- Switch OR gate – LED circuit
- Switch AND gate – LED circuit
- Switch based NAND logic gate – LED demonstration circuit
555 timer is an integrated circuit (IC). Being an IC, it has complex circuitry combined in a single package with external pins/terminals to connect to other circuitry. You can easily make all kinds of fun circuits with just a 555 timer and the components covered above, so I think it’s a good component to learn next.
- 555 Timer IC This particulars of this integrated circuit covered on this page make a lot more sense after you study the basic circuits that follow.
- 555 timer bistable mode – Flip flip basic circuit
- 555 timer monostable mode – One shot
- 555 timer astable multivibrator mode – Flashing LEDs
- 555 timer schmitt trigger logic inverter – NOT gate
- 555 timer LDR controlled astable multivibrator mode LED flasher circuit
- 555 timer – Buzzer output – Astable multivibrator mode – Light dependent resistor LDR controlled circuit
Transistors will probably be the most challenging components to learn. Understanding them will help you understand all of electronics much better, and help you the most in being creative while designing your own circuits.
- NPN BJT switch circuit – Bipolar Junction Transistor – 2N3904
- PNP BJT switch – Bipolar Junction Transistor – 2N3906
- NPN BJT emitter follower circuit – transferring a voltage minus a diode drop
- PNP BJT emitter follower circuit – Transferring weak signal voltage with a diode voltage shift
- Bipolar Junction Transistor BJT voltage follower circuit improved to eliminate base emitter diode shift
- NPN BJT current source – Bipolar Junction Transistor – 2N3904
- PNP BJT current source – Bipolar Junction Transistor – 2N3906
- Schmitt trigger – NPN BJT
- Zener diode component – voltage reference – regulator
- Voltage doubler circuit fragment- Capacitor charge pump – Some V loss
- 7805 5V positive voltage regulator IC
- Battery voltage state of charge SOC – From fully charged to discharged
These pages are still being compiled.
Circuits covered more quickly series:
- Brief polarity indicator LEDs circuit
- Brief capacitor charge and discharge through LEDs circuit
- Brief capacitor charging RC time constant demonstration circuit
- Brief 555 bistable mode flip flop alternating LEDs circuit