You need a continuous conductive path for electricity to flow in order to do something. The entire path that the electricity flows is the circuit.
Note: Never connect the terminals of a power source (such as a battery) directly together. That is called a short circuit and a dangerous amount of current will flow unless it is a weak voltage source. Always have a load that limits the current.
Incandescent light bulb circuit:
Light bulbs aren’t really ever used in basic electronics anymore, but they make a nice illustration circuit for beginners learning electronics.
- Light bulbs are rated for a voltage that can be applied to them. Simply apply that voltage and they will light up.
- Powering the light bulb can be done by using a battery or other power supply that is at the rated voltage of the light bulb or lower.
- Connections. There are light bulb and battery holders that easily allow conductive metal wires to make connections. You can also just touch the metal together to make an electrical connection for experimenting.
- Current: Once the circuit is closed (all needed connections are made), the voltage provided by the battery moves current through the whole circuit based on how much the light bulb limits the current based on the voltage. We imagine a fluid like force flowing from the positive side of the power source, through the wires, load, and back into the battery which keeps pumping the fluid through the circuit. We call that conventional current. After atoms and electrons were discovered, it was realized that electrons actually flow like a fluid from the negative side of the power supply to positive.
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.