SensingDesign rev A, 27 Oct 2026: CAD, fit checks and assembled 3D model done; not built

GuestRoom

One ceiling node per guest room: smoke and vape evidence, AC set back when the room is really empty, and a damp bathroom wall caught early

One ceiling disc in each hotel, rental or serviced-apartment room does three jobs with one brain: it records smoke and vape events with evidence, sets the wall AC back by its own remote codes when a radar says the room is really empty (and uses dry mode instead when the bathroom wall is damp), and warns housekeeping when the bathroom's coldest wall stays at mould-risk humidity.

Who buys it: Owners and managers of small and mid-size hotels, motels, serviced apartments and short-term-rental hosts with wall split or ductless ACs.
Why it pays: Minut puts a hotel smoking incident at $620–1,300; occupancy setback reported nearly $180 a room a year at two Wisconsin hotels (vendor-reported); mould remediation runs $500–10,000+ a room plus nights out of order (trade press). For one room GuestRoom is $329 + $8/month instead of about $547 + $13.50/month for our three products separately.
Target price: $329 per room + $8/room/month (target)
First-minute wow: At 14:10 the room has been empty for 20 minutes, so the AC goes to 26 °C; the bathroom wall is at 78% surface humidity, so it runs dry mode instead of switching off; at 22:14 the same disc records a vape with a curve the guest can be shown.

See the CAD design Concept page

GuestRoom concept: the idea and where each part goes — The concept. The CAD design is below, under Printable CAD.

What the research found

And how this design answers it

Three products, three boxes, three apps (AirMate IR, VapeSense, MouldGuard) → one ceiling disc with one ESP32-C6, one Wi-Fi link, one USB-C supply and one app
AirMate IR's own ESP32-C6, SHT45 and case → a small AC pod with no processor beside the disc, on a 6-core lead
MouldGuard needed its own hub → its wall tag runs on a flat cable over the bathroom door to the disc
Empty-room setback can make a humid room damp → the node uses the AC's dry mode instead of off when the wall is at mould risk
VapeSense's LoRa radio and building gateway → not fitted; hotels and hosts use their own IoT Wi-Fi
Housekeeping overrides undo occupancy savings (BPA study) → radar sees still guests, and the guest's own remote is heard and respected

Use case

A summer day in room 214

Hotel managerHousekeepingGuestGuestRoom node

01Trigger: the guest leaves at 13:50 with the AC on 20 °C; the radar sees nobody, not even someone still in bed
02Decide: after 20 minutes empty the node would set the AC back, but the bathroom wall tag reads 78% surface humidity
03Act: the pod sends the AC's own dry-mode code at 26 °C; when the guest comes back at 18:30 it restores 20 °C
04Evening: at 22:14 a vape event is classified with an evidence card; housekeeping gets a damp-wall note for room 214 the next morning

Outcome: About 4.5 AC hours set back (est.), a wall that dried instead of growing mould, and a smoking fee backed by a record, from one device

How it works

Architecture

01
Sense: Sensirion SEN66 + Bosch BME690 in the disc; HLK-LD2410C radar and a TSOP38238 in the AC pod; SHT45 + NTC in the bathroom wall tag
02
Decide: one ESP32-C6 runs the VapeSense classifier, AirMate's empty-room state machine and MouldGuard's surface-humidity rule
03
Act: four TSAL4400 IR LEDs send the AC's own remote codes
04
Tell: Wi-Fi 6 on the owner's IoT network, MQTT over TLS to one GuestRoom app with events, AC hours and damp trends

Hardware

Real parts, buyable today

Bill of materials: about $116 per room at qty-1 prices including the adapter (est.).

Block	Part	Why this part
Brain	Espressif ESP32-C6-MINI-1 on the VapeSense disc PCB	Already ran the vape classifier; has room for the AC and damp rules and Wi-Fi 6
Air	Sensirion SEN66 + Bosch BME690	Smoke and vape evidence; the SEN66 also gives the room humidity the damp rule needs
Presence	Hi-Link HLK-LD2410C 24 GHz radar	Sees still guests, so the AC is never set back on a sleeping guest
AC control	4 × Vishay TSAL4400 + TSOP38238	Works any split, window or portable AC with its own remote codes
Damp	Sensirion SHT45 + TDK B57861S NTC wall tag	The wall's surface humidity is the mould risk, not the room's
Power	UL-listed 5 V USB-C adapter + 1 F supercap	No mains in printed parts; a last 'power lost' message

Mechanical

Printable CAD

8 parts, generated from code and checked as closed solids. Pick a part to inspect it, or download the STL files to print.

Loading the CAD…

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Open risks we are working on

Radar through a 0.9 mm lid from the ceiling must be proven to see a still guest in bed and not the AC's moving louvres
IR from the ceiling pod must reach the AC's receiver; a second pod angle or a reflector may be needed in long rooms
Shower steam reaching the disc must not be called a vape; the BME690 and RH rules are from VapeSense and unproven
The wall tag's cable over the bathroom door must be neat enough for a hotel; a battery BLE tag is the fallback
Smoking evidence and fees need a policy the guest agreed to; the node gives evidence, the manager decides
Energy savings depend on the AC, the climate and guests; vendor figures vary and one independent study found less

Design stage only: nothing on this page is for sale. Specifications and prices are targets.