First Real Circuits: Guided Build Projects
This is your graduation lesson. Everything you learned in this course — voltage, current, Ohm's law, resistors, LEDs, switches, parallel branches, power, transistors, voltage dividers and capacitors — now comes together in five complete builds that actually do something useful. You will compute first, wire it up, measure with your multimeter, and debug like a real engineer.
Up to now you practised single skills one at a time. A real circuit is just several of those skills stacked together and working at the same time. The secret that separates a confident builder from a frustrated one is a disciplined routine: you never just "plug things in and hope". You predict every voltage and current with a quick calculation, build carefully, measure to check reality against your prediction, and when they disagree you explain the gap instead of panicking. Do this five times and it becomes second nature.
Learning goals — by the end you can:
- Read a parts list and justify every component value with a calculation.
- Compute the resistor for an LED, and currents for parallel branches, from scratch.
- Build a light-sensing night light using a voltage divider driving a transistor.
- Use a capacitor to make a light fade slowly after power is removed, and predict how long.
- Build a continuity tester and use it to find broken wires.
- Predict-then-measure, log results in a table, and debug when numbers don't match.
Every build below follows the exact same six steps. Learning the template matters more than any single project, because you will reuse it for the rest of your life in electronics.