Initial commit: plasma DMD driver project

- Design docs: 12 V DC power supply, safety and bring-up, ESP32 interface, BOM
- PSU schematic (schemdraw) and KiCad 10 carrier-board project with HV net classes
- ESP32 PlatformIO firmware skeleton with HV watchdog toggle
- Reference schematic of the Stern 520-5138-00 display PSU

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/bom.md

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+# Bill of materials
+
+Designators match the KiCad project ([../hardware/kicad/](../hardware/kicad/README.md)).
+Footprint choices are in [gen_kicad.py](../hardware/kicad/gen_kicad.py).
+
+Prices are rough estimates.
+
+## Modules (AliExpress unless noted)
+
+| Qty | Part | Notes | About |
+|---|---|---|---|
+| 1 | 12 V 3 A power brick | **Certified brand, from a local retailer** (e.g. Mean Well GST36A12) | €15 |
+| 1 | Mini560 5 V fixed buck module | Fixed output, no trim pot | €2 |
+| 2 | NCH6100HV nixie HV boost module | Input 9–16 V, output 85–235 V adjustable | €16 |
+| 1 | Isolated DC-DC 12 V → 12 V, 6–10 W | e.g. Mornsun URB1212YMD-6WR3 / -10WR3 | €6 |
+| 1 | 5 V 1-channel relay module, with optocoupler | Switches the 12 V feed to the HV modules | €2 |
+| 1 | Wemos D1 mini ESP32 | | €5 |
+
+## Regulator section (from Mouser / Farnell / Reichelt)
+
+| Qty | Part | Ref (KiCad) | Ref (original Stern board) |
+|---|---|---|---|
+| 2 | MJE15030 (NPN, TO-220) | Q3, Q6 | Q3, Q5 |
+| 1 | MJE15031 (PNP, TO-220) | Q5 | Q4 |
+| 1 | MPSA92 (PNP, TO-92) | Q2 | Q1 |
+| 1 | MPSA42 (NPN, TO-92) | Q4 | Q2 |
+| 2 | 1N5228 (3.9 V zener) | D4, D6 | D3, D4 |
+| 1 | 1N4760A (68 V zener) | D5 | D5 |
+| 1 | 1N4764A (100 V zener) | D8 | D6 |
+| 1 | 1N4743 (13 V zener) | D7 | D7 |
+| 2 | 47 kΩ 1 W | R5, R10 | R2, R3 |
+| 3 | 1.5 kΩ ½ W | R4, R9, R12 | R4, R5, R10 |
+| 2 | 330 kΩ ½ W | R6, R11 | R6, R7 |
+| 1 | 2 kΩ 5 W | R13 | R8 |
+| 3 | 0.1 µF 500 V film | C6, C8, C9 | C3, C4, C7 |
+| 3 | TO-220 heatsink | for Q3, Q5, Q6 | |
+
+## Additions
+
+| Qty | Part | Purpose |
+|---|---|---|
+| 1 | P6KE15A TVS diode (DO-15) | 12 V input surge protection (D1) |
+| 1 | 470 µF 25 V electrolytic | 12 V input bulk (C1) |
+| 1 | 100 µF 10 V electrolytic | +5 V bulk (C2) |
+| 2 | 22 µF 250 V electrolytic (12.5 mm) | Raw HV rail buffer (C5, C7) |
+| 2 | 330 kΩ ½ W | Raw HV rail bleeders (R2, R7) |
+| 2 | LED + 100 kΩ 1 W | HV-present indicators (LED1/R3, LED2/R8) |
+| 1 | 74HCT245 + DIP socket | 3.3 V → 5 V level shifter |
+| 1 | 2N7000, 2 × 1N4148, 100 nF, 10 µF, 100 kΩ | HV watchdog charge pump (Q1, D2, D3, C3, C4, R1) |
+| 2 | 1 kΩ 1 W | Series resistors for first power-up |
+| 5 | 5×20 mm PCB fuse holders + fuses: 3 A T (F1), 2 × 1 A T (F2, F3), 2 × 100 mA F (F4, F5) | |
+| — | Phoenix MKDS 5.08 mm screw terminals: 3 × 2-pin (J1, J6, J7), 2 × 3-pin (J5, J8), 1 × 4-pin (J3), 1 × 5-pin (J4) | Module connections |
+| 1 | Molex KK-396 8-pin header (J2) + mating housing | Panel power |
+| 1 | 2-pin header + jumper (JP1) | +12 V to panel |
+| — | M3 standoffs (H1–H4), 300 V-rated wire, plastic enclosure | |