Regulator v1 — Linear 12 V → 5 V / 3.3 V

Overview

Regulator v1 is the "always plugged in" power source for the breadboard-based PIC10F200 tutorials in Series 1 through Series 4. It takes 12 V from a wall wart and produces two clean rails — 5 V and 3.3 V — that you can jumper straight to a breadboard.

The design is deliberately old-school: a linear LM7805 for the 5 V rail and a TPS79333 LDO fed from the 5 V rail for 3.3 V. That's inefficient at the input voltage, but it's dead-quiet electrically and needs no inductor — perfect for the analog-noise-sensitive experiments in the microcontroller series.

Design intent

• First-PCB approachable: everything is through-hole except the LDO.
• Rock-solid rails: bulk caps on both input and output, plus 100 nF ceramics right at the regulator pins.
• Breadboard-friendly outputs: Phoenix Contact MPT terminal blocks at 3.5 mm pitch on each rail.
• Four-layer for a reason: internal ground and power planes cut noise and give the LM7805 a lot more copper to dump heat into.

Trade-offs vs Regulator v2

	v1 (this board)	v2
Topology	Linear (LM7805 + LDO)	Switching (AP63205 + AP63203 bucks)
Efficiency at 12 V in / 5 V out	~40%	>90%
Output ripple	Very low	Low but not zero
BOM cost	Lowest	Slightly higher
Heat dissipation	Regulator gets warm	Cool to the touch

Choose v1 when you need dead-quiet rails for analog work. Choose v2 when you're running the board off a battery or you want to leave it plugged in 24/7 without heating the room.

Bringing it up

1. Confirm the input jack polarity with a meter before applying power.
2. Power up with no load and verify both rails read within 2% of nominal.
3. Load-test the 5 V rail with a 10 Ω resistor for a few seconds and re-check — the LM7805 will get warm; it should not get hot.
4. Repeat the load test on the 3.3 V rail with 22 Ω.

Manufacturing notes

Four-layer board, standard KiCad Gerbers, 1.6 mm FR-4. The default 1 oz copper is fine for the 500 mA continuous rating; go 2 oz if you plan to run near the LM7805's thermal limit.