# Plasma DMD

Drive a second-hand 128×32 pinball **plasma** dot-matrix display (originally on a Williams WPC
DMD controller) standalone, from a **Wemos D1 mini ESP32**, powered from a single **12 V DC** brick.

The display power supply is built from cheap modules plus a copy of the regulator section of the
Stern/Sega display PSU (520-5138-00). The original transformer and AC front end are not used.

> ⚠️ **High voltage.** The panel runs on about +65 V, −100 V and −112 V, which is about 175 V
> between rails. That can injure you. Read [docs/safety.md](docs/safety.md) before powering anything.

## The panel

- Bought second-hand on 18 September 2021 for €37.
- Originally driven by a Williams WPC DMD controller board. No original controller or PSU came with it.

## Layout

| Path | Contents |
|---|---|
| [docs/power-supply.md](docs/power-supply.md) | PSU design: block diagram, analysis of the original board, changes |
| [hardware/psu-schematic.svg](hardware/psu-schematic.svg) | PSU schematic (generated by [hardware/psu_schematic.py](hardware/psu_schematic.py)) |
| [hardware/kicad/](hardware/kicad/) | KiCad 10 project for the PSU carrier board: schematic and routed PCB (rev 0.1) |
| [docs/safety.md](docs/safety.md) | Safety design (HV watchdog, fusing, layout, bring-up procedure) |
| [docs/esp32-interface.md](docs/esp32-interface.md) | ESP32 pin plan, 74HCT245 level shifter, panel signals |
| [docs/bom.md](docs/bom.md) | Bill of materials |
| [docs/design-review.md](docs/design-review.md) | Design review of the module-only PSU (rev 0.2) and cost estimate |
| [reference/](reference/) | Original Stern 520-5138-00 display PSU schematic |
| [firmware/](firmware/) | PlatformIO project for the ESP32 |
| [CLAUDE.md](CLAUDE.md) | Project notes for Claude: decisions, workflow, tool paths, gotchas |

## Status

> **Paused (2026-10-24)** because of budget and safety concerns. See [docs/design-review.md](docs/design-review.md)
> for the latest review and cost estimate.

- [ ] Identify panel: manufacturer/part number from its label
- [ ] Map the panel's power connector pins (WPC panel ≠ Stern CN2 pinout) and check if +12 V is used
- [ ] Map the panel's 14-pin data connector
- [x] Lay out the PSU PCB in KiCad ([hardware/kicad/](hardware/kicad/README.md))
- [ ] Review the PCB and work through the [before ordering](hardware/kicad/README.md#before-ordering) checklist
- [ ] Order parts ([docs/bom.md](docs/bom.md))
- [ ] Build and bench-test the PSU **without the panel** ([bring-up](docs/safety.md#bring-up-procedure))
- [ ] Build HV watchdog and verify that the relay drops when toggling stops
- [ ] Firmware: row scanning with test pattern
- [ ] First power-up with panel (series resistors, current measurement)
- [ ] Firmware: greyscale, content source (Wi-Fi / serial)