⚡ Power Chain Build Guide

This guide walks you through building a basic AC → DC power chain with a bridge rectifier, filter capacitor, voltage regulator, and load.
Mentors will check your circuit with a multimeter (DMM) and oscilloscope (DSO).

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📝 Step A — Plan (5 minutes)

1. Choose your regulator:

   • 7805 → Fixed 5 V output (simple, common).
   • LM317 → Adjustable output (needs resistors).
   • Switching module → More efficient (if allowed).

2. Prepare heatsink:

   • For 7805, attach a heatsink if current > 100 mA.

3. Select test load:

   • 33 Ω, 5 W → ~150 mA load.
   • 16 Ω, 5 W → ~300 mA load.
   • Add an LED + 330 Ω resistor in parallel as a power indicator.

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🔌 Step B — Build Rectifier

1. Using bridge rectifier IC (easy):

   • Connect AC wires to the ~ ~ pins.
   • + = DC positive, - = DC negative/ground.

2. Using 4 diodes (manual bridge):

   • Arrange 4 diodes in a diamond.
   • AC input to two opposite corners.
   • Remaining corners = +DC and -DC.
   • Stripe side of diode (cathode) points to positive node.

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🛢️ Step C — Add Bulk Filter

1. Connect a large electrolytic capacitor (10,000 µF, 25 V) across DC + and DC –.

   • Long leg = positive.
   • Short leg = negative (ground).
     ⚠️ Check polarity carefully.

2. Add a 0.1 µF ceramic capacitor in parallel (filters high-frequency noise).

3. Add a 100 kΩ, 1 W resistor across the capacitor (bleeder) so it discharges safely after power-off.

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🎚️ Step D — Voltage Regulator

1. Connect DC + to regulator IN, DC – to GND.
2. Take regulated voltage from OUT.
3. Add capacitors close to pins:
   • Input side: 0.33 µF (ceramic) + 10 µF (electrolytic).
   • Output side: 0.1 µF (ceramic) + 10 µF (electrolytic).
4. Attach heatsink if load >100 mA.

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💡 Step E — Load & Indicators

1. Connect 33 Ω, 5 W resistor across +5 V and GND (dummy load).

   • Use 16 Ω, 5 W for higher current (~300 mA).

2. Connect LED + 330 Ω resistor in parallel as a visual "power ON" indicator.

3. Verify:

   • Multimeter (DMM): Output should be ~5.0 V.
   • Oscilloscope (DSO):
     • At capacitor: ripple (sawtooth at 100 Hz).
     • At regulator output: flat line with <50 mV ripple.

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✅ Quick Recap Flow