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Arduino Uno multiplexing four common-cathode 7-segment displays into a 24-hour clock. Buttons on A0 and A1 adjust the hour and minute.

Arduino Uno multiplexing four common-cathode 7-segment displays into a 24-hour clock. Buttons on A0 and A1 adjust the hour and minute.

A complete working torch with 3D enclosure design. Battery, switch, resistor, LED — the classic first electronics project.

A 5-part starter project using the new ESP32 DevKit + hobby servo. GPIO18 drives servo signal, GPIO23 lights a status LED while the code is running.

This is an trial project and first project of this platform

Arduino drives a common-cathode RGB LED through three 330Ω resistors. Code cycles R, G, B via analogWrite — classic PWM color mixing.

The hello-world circuit: 9V battery, 330Ω resistor, LED, ground. Fork it and try a 3V battery, or a 100Ω resistor to watch the LED burn out.

Two 10kΩ resistors in series across a 9V battery. The tap in the middle sits at 4.5V. Try different R1/R2 ratios.

Classic analog circuit — no Arduino. An LDR forms a voltage divider that drives an NPN base. LED turns on only when ambient light drops. Four parts, one transistor, zero code.

Seven Arduino digital pins drive a common-cathode 7-segment display. A shared 330Ω resistor limits current to ground. Code counts 0→9 in a loop.

9V battery, 10kΩ resistor, 100μF capacitor. Time constant τ = 1 second. Open the oscilloscope on V_cap to see the exponential rise.