Input protector

Protect a standard endstop input from a field sensor whose signal may reach 48 V.

Development status

Baseline documentation snapshot: 2026-10-11, before the requested connector/protection/usability revision program. New revision features require their own reviewed source and qualification evidence.

This page documents an unqualified engineering study, not a released or tested product. Saved CAD, renders and automated checks do not establish a safe assembly, compatible cable, firmware support or a usable current rating.

Board-specific qualification limits: v12/18 purchased/16 identity strings match/2 stock blanks;61 selected/584 historical hashes;native0/U1.6 annular contact/startup/fault/thermal/physical open.

Interfaces and wiring

Inputs

  • One nominal digital sensor signal, ground, and optional 5 V; polarity and source impedance unresolved.

Outputs

  • One endstop-style digital output; buffered/open-collector/isolation behavior unresolved.

Connection contract

The table below uses the repository-canonical connector rule: pin 1 is +3.3 V, pin 2 is +5 V, and pin 10 is GND. Do not release a schematic from this table until it is reconciled pin-by-pin with the current V2 Prime connector implementation; current web documentation presents a conflicting ordering.

Pin Function Design note
1 +3.3 V Canonical fixed rail.
2 +5 V Canonical fixed rail.
3 N/A No Gadgeteer interface in this board scope.
4 N/A No Gadgeteer interface in this board scope.
5 N/A No Gadgeteer interface in this board scope.
6 N/A No Gadgeteer interface in this board scope.
7 N/A No Gadgeteer interface in this board scope.
8 N/A No Gadgeteer interface in this board scope.
9 N/A No Gadgeteer interface in this board scope.
10 GND Canonical fixed rail.

Power off before connecting or changing jumpers. Verify pin 1, signal direction, supply voltage and ground at both ends of every cable. A mechanically fitting connector is not proof of electrical compatibility. If a host pin mapping or current allocation remains unresolved in the design record, do not connect the board until it is resolved.

Electrical design requirements

The following are specification requirements or study assumptions; they are not measured operating ratings. A newer selected-revision note takes precedence over historical draft options.

  • 48 V tolerance is required by the source and exceeds the current V2 Prime 3–45 V probe reference.
  • No Gadgeteer connector is specified, so the copied Gadgeteer-5 V jumper note is not implementable as written.

Protection in the design record

The design describes the following protection intent. Check the selected schematic and remaining qualification gates before relying on it:

Protection topology is the design blocker: require reverse polarity, overvoltage, surge, open-wire, and output-current limits.

Selected component architecture

Current v12 review covers24records/18 purchased parts and existing ISO1211 redesign/C2-R8 V1 stock classes. Host5V is mandatory;no successor. Candidate ordering codes/stock reels,U1.6 annular contact,startup/threshold/fault/thermal/independent/physical gates remain open.

Configuration and commissioning

Use the configuration and firmware contract for the exact selected revision. Do not copy another module’s socket assignments or assume that an unused pin is available. First-article work must verify source selection, reset/unplug behavior, cable orientation and the actual load or sensor interface before normal operation.

Requested connector and usability upgrades

The following are requirements for the next design iterations; this page does not claim they are already fitted:

  • On electrically suitable three/four-pin low-voltage ports, provide compact alternative 2.54 mm header/Molex-style and keyed STEMMA-family footprints. Populate one connector option per shared position and document its pin order. Use STEMMA QT only for compatible four-wire I²C; connector appearance does not make another signal protocol I²C-compatible.
  • Assess a third shared jack option on eligible endstop-style ports, with separate header, keyed-connector and jack renders; preserve safe insertion behavior and document any fit exception.
  • Render each supported connector population separately. Document clearances, cable access and the exact fitted option.
  • Use uppercase titles in a consistent Montserrat-style face, labels on both sides, visible domain boundaries, a revision-specific wiring guide and this page’s URL on the silk where readable.
  • Keep mounting-hole centers on a documented 10 mm lattice; add cable-tie holes where space and electrical clearances permit. Place status LEDs near accessible edges and give every indicator its own disable solder jumper. Provide labeled test pads and a ground observation point.
  • Review applicable DC power entries for reverse-polarity cutoff with a blinking warning, overvoltage cutoff/indication, controlled startup and electronic overcurrent protection. Indicator and protection circuits must work in the fault state without defeating isolation or safe output defaults. Thermal protection belongs only where the power/thermal analysis justifies it.
  • Electronic protection does not automatically replace a required mains/branch safety fuse. Backfeed blocking and inductive-load flyback clamps are separate design functions. Do not add identity EEPROMs, fault memory, calibration storage or paid self-test hardware under this upgrade program.

Design sources

Documentation route: smoothieware.org/extensions/input-protector.

Additive design studies

The 2026-10-11 upgrade program has saved additional candidates v13, v14, v15. These studies preserve the historical design described above. Their connector, LED, mechanical and protection changes are revision-specific and remain unqualified.

See the per-board changes, failures and remaining work and mandatory family specification. Use the source hash and native check for the exact candidate being reviewed; do not infer hardware ratings from a rendered population.

Upgrade candidate readback

The three additional revisions are v13, v14, v15. They are engineering studies; saved CAD and renders do not release the hardware. The latest candidate is described below. Older baseline notes above remain historical.

input-protector

  • Latest PCB source, SHA-256 9b2cf62518f1646cd94004ec041362bb1290b4c0141f0fa0778832e5f011aba7.
  • Last native check: 22 errors, including 0 open connections. This is a CAD result, not electrical, assembly or firmware qualification.
  • Alternative connector lands recorded: J2 / JST_PH_B3B-PH-K_1x03_P2.00mm_Vertical. Fit only the selected population; check its pin map and voltage in the design record.
  • normal population/render record: 6 images; source current; image hashes match; 0 unresolved models.
  • stemma population/render record: 6 images; source current; image hashes match; 0 unresolved models.
  • Changes, failed trials and remaining work.

Applicable protection, current-path, thermal, pinout, cable access and physical tests remain open wherever the linked board record has not verified them. A zero native-error count does not close those gates.

Second-round annotation candidate — V17

The additive v17 candidate preserves the protected v16 circuit, component positions, outline and electrical rules. It corrects revision labels and adds a readable complete HTTPS documentation link. Final source-bound parent checks report zero enabled electrical errors, open connections or schematic-parity findings, clean schematic checks and 7 remaining annotation/library warnings. All 12 declared populated/bare views and current manufacturing exports are checked against this source. Earlier component and revision selections on this page remain historical context. Physical fit, current/thermal performance, host compatibility and fabrication qualification remain unverified; no purchasing saving is claimed.

PCB SHA-256: 7a751e4ff74b0e0839c39eb01fac1469d1e11a0a198d2d64d1c1ea48a2a335d9.

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