2026-10-24 02:31:50 +02:00
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# Plasma DMD
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Drive a second-hand 128×32 pinball **plasma** dot-matrix display (originally on a Williams WPC
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DMD controller) standalone, from a **Wemos D1 mini ESP32**, powered from a single **12 V DC** brick.
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The display power supply is built from cheap modules plus a copy of the regulator section of the
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Stern/Sega display PSU (520-5138-00). The original transformer and AC front end are not used.
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> ⚠️ **High voltage.** The panel runs on about +65 V, −100 V and −112 V, which is about 175 V
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> between rails. That can injure you. Read [docs/safety.md](docs/safety.md) before powering anything.
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## The panel
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- Bought second-hand on 18 September 2021 for €37.
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- Originally driven by a Williams WPC DMD controller board. No original controller or PSU came with it.
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## Layout
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| Path | Contents |
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|---|---|
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| [docs/power-supply.md](docs/power-supply.md) | PSU design: block diagram, analysis of the original board, changes |
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| [hardware/psu-schematic.svg](hardware/psu-schematic.svg) | PSU schematic (generated by [hardware/psu_schematic.py](hardware/psu_schematic.py)) |
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| [hardware/kicad/](hardware/kicad/) | KiCad 10 project for the PSU carrier board: schematic and routed PCB (rev 0.1) |
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| [docs/safety.md](docs/safety.md) | Safety design (HV watchdog, fusing, layout, bring-up procedure) |
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| [docs/esp32-interface.md](docs/esp32-interface.md) | ESP32 pin plan, 74HCT245 level shifter, panel signals |
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| [docs/bom.md](docs/bom.md) | Bill of materials |
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| [docs/design-review.md](docs/design-review.md) | Design review of the module-only PSU (rev 0.2) and cost estimate |
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| [reference/](reference/) | Original Stern 520-5138-00 display PSU schematic |
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| [firmware/](firmware/) | PlatformIO project for the ESP32 |
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| [CLAUDE.md](CLAUDE.md) | Project notes for Claude: decisions, workflow, tool paths, gotchas |
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## Status
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2026-10-24 15:07:58 +02:00
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> **Paused (2026-10-24)** because of budget and safety concerns. See [docs/design-review.md](docs/design-review.md)
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> for the latest review and cost estimate.
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2026-10-24 02:31:50 +02:00
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- [ ] Identify panel: manufacturer/part number from its label
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- [ ] Map the panel's power connector pins (WPC panel ≠ Stern CN2 pinout) and check if +12 V is used
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- [ ] Map the panel's 14-pin data connector
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- [x] Lay out the PSU PCB in KiCad ([hardware/kicad/](hardware/kicad/README.md))
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- [ ] Review the PCB and work through the [before ordering](hardware/kicad/README.md#before-ordering) checklist
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- [ ] Order parts ([docs/bom.md](docs/bom.md))
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- [ ] Build and bench-test the PSU **without the panel** ([bring-up](docs/safety.md#bring-up-procedure))
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- [ ] Build HV watchdog and verify that the relay drops when toggling stops
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- [ ] Firmware: row scanning with test pattern
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- [ ] First power-up with panel (series resistors, current measurement)
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- [ ] Firmware: greyscale, content source (Wi-Fi / serial)
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