{
 "version": "2026-10-20",
 "license": "Dimension sheets are written by Xem Studio from the cited sources and are free to use (CC BY 4.0, attribute 'Xem Studio'). Linked files belong to their publishers under the license shown; Xem Studio does not host them. 'license_verified: false' means the license shown is from memory or the publisher's page as last read and should be confirmed at the link before commercial use.",
 "slug": "encoder-disc",
 "name": "Optical encoder disc Ø60, 30 slots, Ø5 bore",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Generators & instruments",
 "year": null,
 "question": "How many slots for an RPM encoder disc, and what size?",
 "tags": [
  "encoder",
  "rpm",
  "optical",
  "slot sensor",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "encoder disc stl",
  "rpm encoder wheel",
  "slotted disc ir sensor",
  "30 slot encoder",
  "tcst2103 encoder disc"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/encoder-disc/",
 "sheet_txt": "https://xemstudio.com/objects/encoder-disc/sheet.txt",
 "sheet": {
  "basis": "Slotted disc for a transmissive IR slot sensor (TCST2103, 3.1 mm gap): Ø60 × 1.5, 30 slots on a 48 mm circle, Ø5 bore",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The disc is Ø60 × 1.5 mm with a Ø5 bore for a Ø5 shaft.",
   "It has 30 radial slots, each 2 mm wide × 6 mm long, centred on a Ø48 circle (from r 21 to r 27), 12° apart: 30 pulses per revolution.",
   "At 1.5 mm thick it passes through the 3.1 mm gap of a TCST2103-type IR slot sensor.",
   "Rpm = pulses per second × 60 / 30."
  ],
  "table": {
   "columns": [
    "feature",
    "size"
   ],
   "rows": [
    [
     "disc",
     "Ø60 × 1.5"
    ],
    [
     "bore",
     "Ø5"
    ],
    [
     "slots",
     "30 × 2 wide × 6 radial"
    ],
    [
     "slot circle",
     "Ø48"
    ],
    [
     "pitch",
     "12°"
    ]
   ]
  }
 },
 "sheet_text": "Optical encoder disc Ø60, 30 slots, Ø5 bore — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/encoder-disc/  (CC BY 4.0)\nBasis: Slotted disc for a transmissive IR slot sensor (TCST2103, 3.1 mm gap): Ø60 × 1.5, 30 slots on a 48 mm circle, Ø5 bore\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The disc is Ø60 × 1.5 mm with a Ø5 bore for a Ø5 shaft.\n- It has 30 radial slots, each 2 mm wide × 6 mm long, centred on a Ø48 circle (from r 21 to r 27), 12° apart: 30 pulses per revolution.\n- At 1.5 mm thick it passes through the 3.1 mm gap of a TCST2103-type IR slot sensor.\n- Rpm = pulses per second × 60 / 30.\n\nfeature  size\ndisc  Ø60 × 1.5\nbore  Ø5\nslots  30 × 2 wide × 6 radial\nslot circle  Ø48\npitch  12°\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Thermocouple — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Thermocouple\n- Wikipedia: Hall effect sensor — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Hall_effect_sensor\n- Wikipedia: Dial indicator — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Dial_indicator\n- Analog Devices: DS18B20 datasheet — PDF — Manufacturer datasheet — https://www.analog.com/en/products/ds18b20.html\n- Long Earth Society: Engine and rig builds — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/encoder-disc/index.json\nAPI: https://xemstudio.com/api/geometry?object=encoder-disc\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Thermocouple",
   "url": "https://en.wikipedia.org/wiki/Thermocouple",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Hall effect sensor",
   "url": "https://en.wikipedia.org/wiki/Hall_effect_sensor",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Dial indicator",
   "url": "https://en.wikipedia.org/wiki/Dial_indicator",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Analog Devices",
   "title": "DS18B20 datasheet",
   "url": "https://www.analog.com/en/products/ds18b20.html",
   "formats": [
    "PDF"
   ],
   "license": "Manufacturer datasheet",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine and rig builds",
   "url": "https://longearthsociety.com/engineering/",
   "formats": [
    "web",
    "video"
   ],
   "license": "LES site",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "hall-sensor-mount",
  "probe-clamps",
  "metric-shafts",
  "crank-discs-5mm-bore"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "metric-shafts",
     "why": "Ø5 bore on a Ø5 shaft (slide)"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "hall-sensor-mount",
     "why": "magnetic pickup instead of optical"
    }
   ]
  }
 ],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [
  {
   "feature": "encoder bore",
   "exact": "Ø5",
   "mates": "Ø5 shaft",
   "fit": "slide",
   "files": "encoder-disc-"
  },
  {
   "feature": "encoder slots",
   "exact": "30 × 2 wide × 6 radial",
   "mates": "IR slot sensor (3.1 gap)",
   "fit": "designed",
   "files": "encoder-disc-"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. Typical FDM: hole +0.0 to +0.1 mm on diameter.",
  "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. Typical FDM: +0.2 mm.",
  "run": "turns or slides in use: pin in a link, rod through a guide. Typical FDM: +0.3 mm.",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. Typical FDM: +0.3 mm.",
  "clamp": "split part that closes on the mating part with screws: make it at size.",
  "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change."
 },
 "faq": [
  {
   "q": "How do I measure RPM with an encoder disc?",
   "a": "Count slot pulses from the IR slot sensor: rpm = pulses per second × 60 / 30 for this 30-slot disc."
  },
  {
   "q": "Will a 1.5 mm disc fit an IR slot sensor?",
   "a": "Yes; the TCST2103 gap is 3.1 mm."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "encoder-disc-30-slots-60mm",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/instrument-mounts/encoder-disc-30-slots-60mm.step",
   "stl": "https://xemstudio.com/files/hardware/instrument-mounts/encoder-disc-30-slots-60mm.stl",
   "note": "optical encoder disc Ø60 × 1.5, 30 slots 2 wide × 6 radial on a 48 mm circle, Ø5 bore (for an IR slot sensor)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/encoder-disc/index.md"
}