KitchenOne: one circuit board of our own

What changed (4 Nov 2026). The rev A bench hood is built from bought boards joined by leads: a XIAO ESP32-S3, an Adafruit MLX90640 heat-camera board, a MAX9814 mic board, an LD2410C radar module, two NeoPixel sticks, a piezo, an ATECC608 board and a PowerBoost 1000C charger. KitchenOne now gets one circuit board of our own, like CricketOne, DampOne and ChillOne, with every chip placed straight onto it. It is the first board made with every shared design-review rule from the start.

• The chips: the ESP32-S3 certified radio module (soldered by its edge pads), a bare Melexis heat-camera chip over the hob, an Infineon 60 GHz radar chip with its antennas built in, a MEMS mic, sixteen call-light LEDs, a sounder, touch electrodes for the fascia’s touch strip, the fan speed line and lamp switch, the security chip, the tamper switch, a charger and two soldered 18650 cell holders.
• The shape: the hood’s front compartment is a long, sealed strip behind the fascia, away from the hot grease filter. So the board is a long main strip (452 × 63.6 mm, 4 layers) lying flat 8 mm above the compartment floor, side A down to the hob, and a front strip (430 × 56 mm, 2 layers) joined by a 60 mm wide flex that bends it 90° up, side A to the room, 7 mm behind the front face.
• Mains stays in the supply. The Mean Well LRS-50-5 that also feeds the hood lamps stays at the compartment’s left end; one latched lead brings 5 V to the board and takes the switched lamp feed back. The hood’s own fan takes our speed line on a second latched lead.
• The rev A bench hood stays as it is. It proves the calls and the software, which move to this board unchanged (same ESP32-S3 family).

The board is code (hardware/pcb/kitchenone-board.mjs). It writes the KiCad board file (hardware/pcb/kitchenone-board.kicad_pcb), the parts list (kitchenone-board-parts.csv) and this drawing, and checks every part:

• every part sits on its strip with a 0.3 mm edge margin and no two parts overlap on the same side;
• every part’s height fits its side: 7.5 mm under the main strip, 77.5 mm above it, 6.5 mm in front of the front strip;
• the heat camera, the mic and its gasket and the sounder sit on their holes in the hood’s underside, and the radar chip, the call-light LEDs, the tamper switch and the touch electrodes on their windows in the front (within 1 mm, from cad/kitchenone-cad.mjs);
• the fold keeps the front strip inside the compartment, 7 mm behind the front face and below the ceiling, and the main strip 8.5 mm clear of the supply;
• the radio module’s antenna end is at the main strip’s front edge, with a keep-out under it and a copper-free window on the front strip in front of it;
• the radio, the power block and the supply lead are 30 mm or more from the heat camera (91 mm in this layout), so a warm board does not offset the hob readings.

KiCad design rule check: 0 violations (KiCad 10, 4 Nov 2026). Each part is drawn at its real size, as a placeholder outline until its full footprint is added. Numbers marked est. are estimates.

1. The shape: a main strip and a front strip in the hood’s front compartment

Why this shape: the compartment is the only part of the hood out of the hot, greasy air path. Its floor carries the holes that look and listen down at the hob, and its front carries the windows to the room. One strip on the floor and one bent up behind the front reach every hole and window without a second board.

Nothing in the hood CAD changes for this board. Every hole and window it uses is already in cad/kitchenone-cad.mjs rev A (Ø14 heat window, mic port, tone holes, radar window with a 1.5 mm skin, opal slot, tamper hole, touch strip). The CAD alignment with the board inside the hood (rev T) is the next step.

2. What is on the board

The S1 sensor core (radio module, radar chip, power block, security chip and software), in KitchenOne’s shape.

What is different for a range hood:

• One heat-camera chip over the hob. The bare MLX90640 is the same sensor as the Adafruit board without the breakout, soldered through the board over the Ø14 window.
• Radar on the board. The LD2410C was a module on pins; the BGT60TR13C has its antennas in its package and sees the room through the 1.5 mm fascia skin.
• A mic chip in place of a mic board. It hears whistles and the home’s own smoke and gas alarms as sound patterns; nothing is recorded.
• Backup cells on the board. The PowerBoost board and loose cells become a charger chip and two soldered holders with a thermistor: a gas hob keeps burning in a power cut, so the hood keeps watching.
• A touch strip. The fascia’s recessed strip reads through four copper pads on the front strip, so lamp, fan and silence need no buttons or holes.

3. Every connection, checked

Our rule: every pair of parts that join is checked against both makers’ drawings and a search for known problems. No “same as DampOne” claims.

No adapters, no plug-in modules and no ribbons inside.

4. Heat

• The board draws about 0.9 W watching (est., section 5). The problem is the hood, not the board: steam and hot air rise round the canopy while cooking, so the compartment is counted at 55 °C (est.).
• The ESP32-S3 at 0.5 W reaches about 65 °C (est.), inside its 85 °C rating.
• The cells sit at the compartment’s right end, away from the heat window. Charging holds above 45 °C (RT1 on the BQ24074) and resumes when cooking ends; the cells are rated to 60 °C while discharging.
• The heat camera reads the hob, not the board: the radio, the power block and the supply lead are 91 mm or more from its can.
• Rev A logs the compartment temperature over a real gas hob at full boil for an hour.

5. Power budget (est.)

6. Factory test (every board, every time)

1. Current-limited first power-on (100 mA). A short trips in about 1 s, before anything heats.
2. Every rail within ±3 %; reverse 5 V does no harm. Charger: charge current, the thermistor’s hold at a hot and a cold resistor, power-path switch-over with 5 V removed.
3. Our small loader flashed over the USB pads; our microSD card in, then boot: the loader starts our program from the card.
4. Heat camera: a warm and a cold plate under the window position; every pixel answers. Radar: a moving plate at 1 m and 3 m. Mic: a test tone and a smoke-alarm pattern. Each LED colour read by a light sensor; the sounder’s level; each touch pad.
5. Fan PWM out and tach in on a test fan; the lamp switch on a test load. The tamper switch opened and closed. The flex bent to 90° and back once, then the front strip checked again.
6. Wi-Fi to the fixture. The unit’s own key goes into the security chip, the ID chip is written and the label is printed. Every result is stored against the serial number.

For each rev A batch: radio pre-scan (FCC Part 15, UK and EU radio rules, and the 60 GHz radar rule), a 24-hour soak at 55 °C in steam, and the hood’s own electrical safety pre-checks.

7. Who makes what

8. Cost per hood, electronics (est.)

The heat-camera chip is the biggest single part (about $30–35 at volume, est.). The two long strips make the board larger than it needs to be in area; a rev B option is a shorter front strip with the tamper switch moved next to the radar, once the hood CAD can move the tamper hole.

9. Timeline

10. Still to check

1. The bare MLX90640ESF-BAA can’s exact outline, lead pitch and land pattern from the Melexis datasheet (here Ø9.4 × 6.6, est.).
2. The Micro-Fit 3.0 header part number, footprint and pin order, and the hood fan’s own speed input and connector.
3. The Keystone 18650 SMT holder’s outline and pads (here 77 × 21 × 21, est.).
4. The flex’s minimum static bend radius from the chosen maker against the 3.8 mm used here.
5. Wi-Fi range from inside the steel hood, out through the fascia, to a home router (measured on rev A).
6. The compartment temperature over a gas hob at full boil, and the cells’ temperature in it.
7. The CAD alignment (the board in the hood CAD, every part checked in 3D, rev T) and the product page’s 3D board model, as done for DampOne.

Sources

• Espressif ESP32-S3-WROOM-1 datasheet (18 × 25.5 × 3.1)
• Melexis MLX90640, 32 × 24 thermal sensor (BAA: 110 × 75° view)
• Infineon BGT60TR13C, 60 GHz radar, antennas in package, 6.5 × 5.0 × 0.9
• Infineon IM69D130 MEMS microphone
• TI BQ24074 charger with power path
• TI TPS63020 buck-boost converter
• Keystone 18650 cell holders
• Samsung INR18650-35E specification
• Molex Micro-Fit 3.0 connectors
• Microchip ATECC608B
• Omron D2F datasheet
• Mean Well LRS-50 datasheet
• The hood, its sizes and its calls: KitchenOne’s design
• The board platform: our own boards

Design review (4 Nov 2026)

Every board is checked by the same rules (products/_shared/board-rules.mjs), one for each lesson any of our boards has taught us. KitchenOne’s board was made with every rule from the start, so nothing had to be fixed. The full review, with every number and its source, is on the board page. It shows:

• Heat camera pixels: a 16 cm pan on the farthest burner fills 3.5 px; a lit burner with nothing on it (the 9 cm flame ring at 0.76 m) fills 2.0 px against a 1.5 px need, because a flame only has to be found, not measured.
• Power cut: two cells give about 25 h of alerts aged to 80 % (to prove on rev A; target 24 h), since a gas hob keeps burning when the power goes.
• Cells in a hot hood: charging holds above 45 °C and resumes after cooking (to prove over a real hob).
• The latched microSD (J2) is fitted, and our software starts from it.
• Conformal coating against steam and grease is asked for in the quote.
• Wi-Fi from inside the steel hood is measured on rev A; the antenna sits under the plastic fascia with a copper-free window in front of it.
• The tamper switch against the fascia boss is checked with the printed fascia on rev A.
• Fast lines on a solid ground plane (to prove, lesson: planes, from the CricketOne test-board layout of 4 Nov 2026): USB (90 Ω); antenna feed (50 Ω, keep-out on every layer); card lines (length-matched, no vias under the socket). Ground on the layer next to the parts (inner layer 1, supply on inner layer 2; the whole bottom of a 2-layer section), one via beside each ground and supply pad and none in pads, no copper or vias in the antenna keep-out on any layer or under the card socket, the impedance lines routed first with a test coupon. The quote asks for it; the routed board’s design rule check proves it.

The request for quote is /build/kitchenone-quote.

New shared rule (4 Nov 2026, from PumpOne): antennas outside metal boxes. A radio inside a closed metal enclosure now fails the review unless its antenna is outside the metal. This board’s antennas already use the strip’s front edge under the plastic fascia, so the check passes and the review names the window (lesson: enclosure).