73 lines
4.6 KiB
Markdown
73 lines
4.6 KiB
Markdown
# Plasma DMD — notes for Claude
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The goal: drive a second-hand 128×32 pinball **plasma** DMD panel standalone from a **Wemos D1 mini ESP32**,
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powered from **12 V DC only**. The panel was originally on a Williams WPC controller and was bought on
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2021-09-18 for €37. No original controller or PSU came with it.
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## Status (keep this section up to date)
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- **PAUSED (2026-10-24)** at the user's request, because of the cost and the safety risk. If resuming, consider the
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cheaper, no-high-voltage alternative discussed: a 128×32 HUB75 LED matrix driven by the same ESP32 (about €30–50).
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- Design docs in `docs/`, PSU schematic and routed PCB rev 0.1 in `hardware/kicad/`, firmware skeleton in `firmware/`.
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- Not yet known: the panel's make and part number, its power and data connector pinouts, and the
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polarity of its control signals. **J2's pinout is a placeholder (Stern CN2 order).**
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- Nothing is built or tested on real hardware.
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- **Proposed rev 0.2: module-only PSU** (no linear regulators or heatsinks), reviewed in `docs/design-review.md`.
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It's waiting on the must-fix items M1–M4 there. The schematic and PCB are still rev 0.1.
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## Design decisions (don't silently change these)
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- **PSU:**
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- A 12 V brick feeds a Mini560 (5 V) and two NCH6100HV boost modules: one at 90 V, and one at
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130 V fed through an isolated DC-DC, so its output floats and becomes −130 V.
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- Those raw rails feed a copy of the regulator section of the Stern 520-5138-00 (zener-referenced
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followers), giving about +65 V, −112 V and −100 V.
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- The zeners set the panel voltages, not the module trim pots.
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- **Modules sit off-board** on screw terminals. The PCB is a carrier board.
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- **Safety first:**
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- A relay switches the 12 V feed to the HV modules.
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- The relay is driven by a hardware charge-pump watchdog, toggled by GPIO21 once per scanned row
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(about 2 kHz). If toggling stops, the HV drops.
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- Bleeders and fuses on every HV rail.
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- **Clearances** (`hardware/kicad/plasma_dmd_psu.kicad_dru`):
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- 3 mm between HV and LV, 1.3 mm between HV nets.
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- Documented exceptions only inside or next to transistor and connector pins.
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- **TO-220 tabs and heatsinks are live.** Each heatsink pin is on its collector net.
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- **Track widths** come from IPC-2221 against the fuse currents (see `hardware/kicad/README.md`).
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## Workflow and tools
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- KiCad 10: `C:/Users/patri/AppData/Local/Programs/KiCad/10.0/bin/` (`kicad-cli.exe`, and `python.exe` with `pcbnew`).
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- Freerouting 2.5.0 jar: `tools/freerouting/`, git-ignored. It needs **Java 25**:
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`C:/Program Files/Eclipse Adoptium/jre-25.0.4.101-hotspot/bin/java.exe`.
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- Pipeline (KiCad must be closed while the scripts run):
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1. `python hardware/kicad/gen_kicad.py` writes the schematic and the project net classes from `PARTS`.
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It **keeps symbol UUIDs**, so the PCB stays linked.
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2. `python hardware/kicad/check_netlist.py` verifies every pin's net through kicad-cli.
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3. `<kicad python> hardware/kicad/layout_pcb.py` adds, swaps and places footprints from `PLACE` and draws
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the outline and silkscreen. **It deletes tracks and zones.**
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4. `<kicad python> hardware/kicad/route_pcb.py [passes]` runs Freerouting:
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- It routes with oversized tracks and vias, then shrinks them, which yields the clearances.
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- It adds J2 escape stubs and heals T-junctions.
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- It adds the bottom GND pour.
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5. `kicad-cli pcb drc --schematic-parity --refill-zones hardware/kicad/plasma_dmd_psu.kicad_pcb`.
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The target is 0 errors. The 9 silkscreen warnings (TO-220 outline over the heatsink pins) are known.
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- Once the user starts hand-editing the schematic or PCB in KiCad, stop regenerating with the scripts.
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## Gotchas learned the hard way
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- Bash heredocs passed through the tool can collapse `\\` and `\n` escapes. For Python with regexes
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or escapes, use the Write/Edit tools, not `python - <<EOF`.
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- pcbnew: use `board.Delete(item)`, not `Remove` (Remove leads to segfaults). `GetTracks()` throws
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`TypeError` when empty. Copy coordinates out of an item before deleting it.
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- KiCad schematic text needs `\n` escapes, not raw newlines, or the file won't load.
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- Freerouting puts fixed stubs back in the SES (duplicates). Its SES can silently omit a net when routing
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is incomplete, so always check DRC for unconnected pads.
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- MKDS terminal blocks: wire entry is on the footprint's +y side.
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## User preferences
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- Commit only when the user asks. Initial commit `dbc1f00`, PCB rev 0.1 `28c6665`. Remote: `origin` = https://mangavalk.com/mangavalk/Plasma-DMD.git (branch `main`).
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- Before changing a file the user may have edited, check their edits first and keep them.
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