Great question 👍 Let’s go through each of these circuit diagrams one by one
in simple terms:
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Image 1
🔋 Battery Level Indicator Circuit
Power source: 3.7V Lithium battery.
Components:
BC547 transistor (acts like a switch/amplifier).
Resistors (220Ω, 1kΩ, 2.2kΩ) – limit current and control base voltage.
LEDs (Red & Green) – show status.
Diodes (1N4007) – protect against reverse current.
Working:
The red LED indicates low battery.
The green LED lights when voltage is sufficient.
The transistor switches the LEDs depending on battery voltage.
👉 Basically, this is a simple battery level indicator circuit.
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Image 2
🔔 Simple Switch-Controlled Circuit
Power source: 9V battery.
Components:
Switch – to turn ON/OFF.
Buzzer / Lamp – load device.
Working:
When the switch is closed, current flows → buzzer/lamp turns ON.
When the switch is open, the circuit is broken → device OFF.
👉 This is a basic closed and open circuit example.
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Image 3
🔋 Auto Cut-Off 3.7V Lithium Battery Charger
Power source: USB 5V input.
Components:
TL431 (voltage reference IC) – controls charging cutoff.
IRFZ44N MOSFET – works as an electronic switch.
Resistors – set voltage threshold.
LEDs (Red & Green) – charging/full indicators.
Working:
Red LED ON → battery charging.
When battery reaches full voltage (4.2V approx.), TL431 triggers cutoff.
Green LED ON → battery full, charging stopped.
👉 This is an automatic lithium battery charger circuit without a relay.
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Image 4
💡 Simple Lamp Control Circuit
Components:
Generator (G) – supplies current.
Switch – controls ON/OFF.
Lamp – load.
Wires – connect components.
Working:
Switch closed → generator current flows → lamp ON.
Switch open → no current → lamp OFF.
👉 This is a very basic circuit showing current flow control.
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Image 5
⚡ 12V DC to 220V AC Inverter Circuit
Power source: 12V battery.
Components:
Switch – to control ON/OFF.
Transistors (TIP41C x 2) – work as oscillators/amplifiers.
Resistors (330Ω, etc.) – control current.
Transformer (12-0-12 input / 220V output) – steps up voltage.
Working:
Battery supplies 12V DC.
Circuit oscillates transistors → produces AC pulses.
Transformer steps up 12V AC pulses → 220V AC output.
Can power small appliances like bulbs.
👉 This is a basic inverter circuit (DC to AC conversion).
