Chapter 07
Fabrication
The prototype is printed at home, on a Bambu Lab P2S, and assembled without any electronic soldering. The plans, the parts, the assembly, the bill of materials and the budget.
The plans
Views taken from the real model
Download the plans (PDF, 8 pages)
Technical plans for the V1, version of 9 November 2026: dimensioned views, section, parts, fabrication, wiring, assembly order, safety and test checklist. Dimensions in millimetres.
Printing
Six print plates on the Bambu Lab P2S
The P2S prints several colours in the same part thanks to its spool changer (AMS 2 Pro): this is what makes the translucent front panel with its integrated black block possible. Three filaments: PETG Matte in white and black, and PETG Translucent. The parts weigh about 365 g in total. A test piece goes first, to validate the clearances for the screws, the magnet and the shutter before the large parts.
Plates
- 1. Test pieces: inserts, brass seen through the shell, clearances for the screws, the magnet and the shutter
- 2. Translucent front with black block
- 3. Back and wall plate
- 4. Small parts: frame, shutters, buttons, clips
- 5. Box no. 2: white front
- 6. Box no. 2: back
Files ready to open in Bambu Studio: 03-plans/impression-V1/bambu-P2S/. Everything is printed at home.
Parts
| Part | Qty | Dimensions (mm) | Volume | Orientation and remarks |
|---|---|---|---|---|
| Front | 1 | 76 × 76 × 125 | 84.2 cm³ | Diamond front flat on the build plate, vertical sides. The front face carries the perforations and the fabric recess: it must stay clean. |
| Back | 1 | 97 × 88 × 110 | 50.3 cm³ | Flat top against the plate; wall plates and the Pi partition vertical. The Ø10 magnet holes may sag slightly at their top: acceptable. |
| Wall plate | 1 | 65 × 61 × 61 | 15.9 cm³ | One wing flat; mushroom studs chamfered at 45°. |
| Lens frame | 1 | 23 × 23 × 2 | 0.5 cm³ | Small part (Ø23 mm): front face on the plate. |
| Shutter | 3 | 24 × 24 × 4 | 0.3 cm³ | 1 mm plate with a Ø2.2 mm stem: fragile, hence 3 copies. |
| Button | 3 | 5 × 5 × 1 | 0.0 cm³ | Tiny (Ø5 mm): 3 copies, possibly with a brim. |
Source: 03-plans/impression-V1/pieces.json (9 Nov. 2026). Shutters and buttons in three copies: they are very small, fragile parts.
Assembly
Step by step, in 3D
No electronic soldering: Dupont wires and a ribbon cable. The front, which is opened often on the stand, screws into 3 brass inserts set with a soldering iron; the Pi and the camera screw into plain pilot holes. Detailed assembly order in the plans (PDF).
Bill of materials
What was bought
| Item | Role | Qty | Unit price | Retailer |
|---|---|---|---|---|
| Electronics | ||||
| Raspberry Pi 5, 4 GB | The device's computer: records, finds the child, keeps useful moments | 1 | €136.80 | Kubii |
| Official Active Cooler | Cools the Pi 5 under continuous load | 1 | €6.00 | Kubii |
| Official 27 W USB-C power supply (EU, white) | Certified power supply, outside the device | 1 | €12.90 | Kubii |
| Camera Module 3 Wide | 12 MP wide-angle camera (120° diagonal, 102° horizontal) | 1 | €39.60 | Kubii |
| Pi 5 camera cable, 200 mm | Connects the camera to the Pi 5 (22 → 15 pins) | 1 | €1.32 | Kubii |
| Official 32 GB microSD card | Operating system and device software | 1 | €34.20 | Kubii |
| Female-female Dupont wires 10 cm (40-way) | Solder-free wiring of the light | 1 | €2.50 | Kubii |
| 90° angled USB-C adapter (Delock 60287) | Lets the power plug fit inside the device while carrying the Pi 5's 5 A | 1 | €7.14 | Reichelt |
| RGB LED module 5050 (built-in resistors) | Recording light with adjustable colour (1 spare) | 3 | €1.46 | Reichelt |
| Mini USB microphone 22 × 19 × 4 mm (794 / Sxhlseller) | Sound, plugged straight into a Pi USB port | 1 | €10.04 | Amazon.fr |
| Fixings and finishing | ||||
| Cable ties 100 × 2.5 mm | Strain relief for the power cable | 2 | €0.05 | Reichelt |
| Cyanoacrylate glue (12 g pen) | Magnets, lens frame | 1 | €7.82 | Reichelt |
| Extra-strong spray adhesive 500 ml | Glueing the fabric on the diamond | 1 | €12.71 | Reichelt |
| Black acoustic fabric 150 × 75 cm | Being restocked: replaced by the VIGAN fabric; to cancel if Audiophonics agrees (2 pieces) | 2 | €4.89 | Audiophonics |
| M2.5 × 6 stainless socket-head screws (bag of 10) | Fixing the Pi 5 on its 4 standoffs (machine screws into the Ø2.2 pilot holes) | 1 | €0.90 | Audiophonics |
| M2 × 5 button-head steel screws (bag of 10) | Fixing the camera (4 machine screws into the Ø1.6 pilot holes) | 1 | €1.50 | Audiophonics |
| Black acoustic mesh fabric, 1 × 1.6 m (VIGAN) | Fabric front of the diamond (replaces the fabric being restocked); check on arrival that it fits the 0.8 mm recess | 1 | €17.89 | Amazon.fr |
| Brass threaded insert kit M2–M8 + adjustable 80 W soldering iron (180–500 °C), VTSHENY | Heat-setting the front's 3 M2.5 inserts (no electronic soldering); inserts without published dimensions: to be measured | 1 | €29.99 | Amazon.fr |
| M2.5 × 8 stainless countersunk Torx TX8 screws, ISO 14581 (pack of 20), PRORAJE | Front → back closure into the inserts (3 per box + spares) | 1 | €7.20 | Amazon.fr |
| Neodymium magnets 10 × 2 mm (pack of 52), Magenesis | Centring the device on its bracket (4 needed, the rest spare) | 1 | €11.99 | Amazon.fr |
| Filament and spools | ||||
| Bambu Lab PETG Matte white refill, 1 kg (35100) | Back, bracket, shutters, buttons and the whole second box (≈ 255 g used) | 1 | €16.12 | Bambu Lab (boutique UE) |
| Bambu Lab PETG Matte black refill, 1 kg (35101) | Black block inside the translucent front, lens frame, cable clips (≈ 20 g + AMS purges) | 1 | €16.12 | Bambu Lab (boutique UE) |
| Bambu Lab PETG Translucent clear refill, 1 kg (32101) | Translucent shell of the V1 front and test pieces (≈ 103 g) | 1 | €17.13 | Bambu Lab (boutique UE) |
| Bambu Reusable Spool | Required: a refill only loads into the AMS 2 Pro once mounted on a spool (1 per colour) | 3 | €14.11 | Bambu Lab (boutique UE) |
| Durable tools (reusable beyond the prototype) | ||||
| Calliper | Measuring inserts, screws and printed parts to adjust the holes | 1 | €11.99 | Amazon.fr |
| Side cutters | Cutting print supports and cable ties | 1 | €5.99 | Amazon.fr |
| Deburring tool | Deburring holes and edges of printed parts | 1 | €8.99 | Amazon.fr |
| Needle files | Fitting the shutter slide and the holes | 1 | €5.49 | Amazon.fr |
| A2 cutting mat | Cutting the fabric and working on the parts | 1 | €21.93 | Amazon.fr |
| Scraper | Finishing the printed parts | 1 | €19.99 | Amazon.fr |
| Posca markers | Marks and touch-ups | 2 | €4.36 | Amazon.fr |
Everything is ordered (9 and 10 November 2026). Prices including VAT actually paid, taken from the order confirmations (04-achats/liste-achats.json).
Budget
What the prototype cost
Result
€468.96
for the prototype, including shipping: €446.46 of parts and €22.50 of shipping. On top of that come €83.09 of reusable tools, making €552.05 of purchases in all. The printer, bought separately, is not included.
| Category | Amount incl. VAT |
|---|---|
| Electronics | €254.87 |
| Fixings and finishing | €99.89 |
| Filament and spools | €91.70 |
| Shipping | €22.50 |
| Prototype | €468.96 |
| Durable tools | €83.09 |
| Total purchases | €552.05 |
Running costs
What using it costs
The only measured figure
0.3 cent
(US) per minute of video: this is what Gemini's HIGH setting adds, chosen to see details better (study 05.4). Calculation: 198 more tokens per second (289 at HIGH against 91 at LOW, measured on 9 November 2026), × 60 s, × $0.25 per million tokens, the input price of gemini-3.1-flash-lite. That is $0.00297 per minute.
Not yet calculated
- The cost of a full analysis: the audio, the prompt and the response are not counted above.
- The cost per family per month.
- The selling price of the Sensor.
Sources: 00-journal-de-conception/recherches/2026-11-09_test-gemini-video-adulte.json (measured tokens); Gemini API pricing page (read on 10 Nov 2026); calculation in recherches/2026-11-10_cout-reglage-high.md.
Schedule
Four weeks, counted backwards
Figure 7
From 9 November to the departure on 7 December
Each bar is a task. The critical path, in orange, cannot slip without pushing back the departure.
03-plans/planning.md, 9 Nov. 2026. Decision point on 12 November, with tracking of the printer's parcel.