StudyOne: one circuit board of our own
What changed (4 Nov 2026). The rev A bench lamp is built from bought boards joined by leads: a Raspberry Pi Zero 2 W, a Camera Module 3 Wide on its ribbon, an SPH0645 mic board, a Pololu VL53L1X board tilted on the cover, a VEML7700 board, three NeoPixel sticks, an ATECC608 board and a MAX98357A amp board in the base. StudyOne now gets one circuit board of our own, like CricketOne, ChillOne and BedsideOne, with every chip placed straight onto it, made with every shared design-review rule from the start.
- The chips: the V1 core (Rockchip RV1126B, 1 GB LPDDR4X, 8 GB eMMC, AMPAK AP6256 Wi-Fi/BT module), a bare Sony IMX415 8 MP camera chip under an M12 lens holder (the C1 camera on the board), an ST VL53L1X eye-distance chip, a Vishay VEML7700 page-light chip, an Infineon IM69D130 MEMS mic, 16 white reading LEDs and their flicker-free driver, 8 call-light LEDs, the MAX98357A speaker amp, the security chip, the tamper switch and a USB-C power-only inlet.
- The shape: the lamp’s electronics live in two places, so the board does too. A head board (358 × 50 mm, 8 layers) lies flat in the hollow steel head arm, 12 mm over the opal head cover, looking down at the page. At its front end a 12 × 12 mm eye tab sits in a U-slot on a 2 mm flex hinge and is folded 45° down, so the eye-distance chip looks out at the child’s head. An 18 mm tail (about 508 mm, est.) runs back to the column and down it to a base board (80 × 60 mm, 4 layers) in the base, behind the column, with the USB-C inlet at the back wall and the speaker amp.
- Only 5 V in the lamp. Power comes from a listed 5 V 3 A USB-C adapter at the wall (a child’s lamp is SELV only, IEC 60598-2-10). No cells: a desk lamp does not need to run in a power cut.
- Made from the shared rules: MEMS clocks, the latched microSD card with our software on every board, conformal coating against a spilt drink, the antenna checked for the steel head on rev A, warm parts 20 mm or more from the camera chip.
The bench lamp stays the test rig until the boards arrive.
1. The shape: three pieces on one board
| Piece | Size | Layers | Where | What |
|---|---|---|---|---|
| Head board | 358 × 50 mm, 1.6 mm | 8 | flat in the head arm, side A 12 mm over the cover, side B 9.4 mm under the arm’s top wall | the V1 core, camera chip, lights, sensors, card, security |
| Eye tab | 12 × 12 mm, 0.8 mm, on a 2 mm flex hinge | 4 | U-slot at the head board’s front end, folded 45° down | VL53L1X eye-distance chip |
| Tail | 18 mm wide, about 508 mm (est.) | 2 (flex) | from the head board’s back edge, back 22 mm to the column, down the 24 × 24 column, forward 16 mm in the base | 5 V (3 A), I2S to the amp, ground |
| Base board | 80 × 60 mm, 1.6 mm | 4 | flat in the base behind the column, side A 2.2 mm over the base plate | USB-C inlet, eFuse, speaker amp, speaker pads |
The eye tab’s hinge is solved in the board code (studyone-board.mjs) so that the chip’s axis meets the eye-distance window centre exactly; the folded tab’s lowest corner is 3.7 mm above the cover.
2. What is on the board
Head board, side B (up, to the steel arm): RV1126B (U1) with a 20 × 20 aluminium heat block and gap pads to the arm’s top wall (HS1), LPDDR4X (U2), eMMC (U11), the power rails (U3), 24 MHz and 32 kHz MEMS oscillators (Y1, Y2), AP6256 Wi-Fi/BT (U5) with its chip antenna at the board’s left edge (keep-out on both sides), ATECC608B (U8) and the ID chip (U9), the LED level shifter (U36), the reading-light driver (U13), the mic (MK1) over a hole through the board, the camera’s three LDOs and its MEMS oscillator (U21–U23, Y20), factory pads (TP1).
Head board, side A (down, to the opal cover): the IMX415 camera chip (U20) under an M12 lens holder with a 90° × 59° lens (LH1) over the camera window; 16 white 2835 LEDs, 4000 K, CRI 95, over the two thinned opal strips (D1–D16, the reading light); 8 WS2812B-class LEDs over the call-light strip (D17–D24: green tick, amber “look again”, blue break); the VEML7700 (U24) under a Ø3 light pipe (LP1) to the page-light window; the mic gasket (GK1) to a new mic port; the D2F-01 tamper switch (SW1) on a cover boss; the latched microSD socket (J1), reached by taking off the head cover; the RV1126B decoupling field (C1).
Eye tab: VL53L1X (U12) on side A, its LDO and pull-ups (U14) on side B.
Base board: the USB-C power-only receptacle (J2) with its mouth at the back inlet, the eFuse and TVS (U30), the bulk capacitors and ferrites for the tail (U32), the MAX98357A amp (U31) and the speaker wire pads (PD1); factory pads on side A (TP2).
3. Every connection, checked
| Link | How | Checked against |
|---|---|---|
| Camera chip to RV1126B | 4-lane MIPI CSI-2 on the head board, 100 mm of track | IMX415 data sheet: 891 Mbps per lane; the review uses 0.41 Gbps of 3.56 |
| Eye-distance chip | I²C across the 2 mm flex hinge | ST VL53L1X data sheet (2.8 V supply on the tab) |
| Page-light chip | I²C, light pipe Ø3 to the window | Vishay VEML7700 data sheet |
| Mic | PDM, bottom port over a Ø1 hole, gasket to the cover port | Infineon IM69D130 data sheet |
| Speaker amp | I2S down the tail, 508 mm, with ground lines between | MAX98357A data sheet; slow clocks (3 MHz) on a two-layer flex |
| Reading light | constant current, analogue dimming | the driver’s data sheet (to choose); no PWM, so no flicker |
| Call light | one data line, 3.3 → 5 V level shifter | WS2812B data sheet |
| Power in | USB-C, 5.1 kΩ CC pull-downs, 5 V up to 3 A, eFuse at 3.5 A | USB Type-C spec 2.x (power-only sink); the adapter is listed |
| Card | SD bus to the RV1126B, latched socket | Amphenol 101-00660 family drawing |
Every mating pair is checked against the makers’ documents, never “same as” another board.
4. Heat
The steel head arm is the heat sink: about 1.2 W from the RV1126B goes through the heat block into the arm (8 K/W est.), so the chip sits near 50 °C with the arm at 40 °C inside. The 16 reading LEDs (3.2 W at full) warm the arm from below; the arm’s touch temperature is logged on rev A against IEC 60598-2-10. The camera chip is 25 mm from the nearest reading LED and 204 mm from the processor.
5. Power budget (est.)
| State | Draw |
|---|---|
| Watching (RV1126B, camera at 5 fps, Wi-Fi) | 1.5 W |
| Reading light at full | 3.2 W |
| Call light | 0.3 W |
| Speaker peak (a word or the break chime) | 1.5 W |
| Peak | 6.5 W, 43 % of the 15 W adapter |
| Lamp off, waiting for the child (camera and LEDs off) | 0.4 W |
6. Factory test (every board, every time)
Spring-pin fixture on TP1 and TP2: 5 V in through the USB-C, the eFuse trip at 3.5 A, every rail, boot from the card, the camera frame of a test page at the lamp’s height, the eye-distance chip against a target at 250 mm, the page-light chip under a 500 lux lamp, the mic against a 1 kHz tone, the amp into a test speaker, all 24 LEDs, the tamper switch, the security chip’s key, the Wi-Fi link. The board gets its serial number in the ID chip.
7. Who makes what
One maker makes the rigid-flex board and assembles it (turnkey). We supply the microSD cards with our software and the lens holders’ lenses focused at 450 mm (est.). The quote pack is /build/studyone-quote.
8. Cost per lamp, electronics (est.)
| Item | Cost |
|---|---|
| V1 core (RV1126B, LPDDR4X, eMMC, power, AP6256) | $30 |
| IMX415 camera chip, holder and lens | $14 |
| VL53L1X, VEML7700, mic, amp, security, ID | $9 |
| 24 LEDs and the reading-light driver | $5 |
| USB-C, eFuse, socket, switch, passives | $5 |
| Board (8-layer head, 4-layer tab and base, long tail), 1,000 lamps | $22 |
| Assembly and test | $9 |
| microSD card with our software | $4 |
| Total | about $98 per lamp (est.) |
The bench lamp’s bought boards cost about $130 at qty 1, so the board is about $32 cheaper per lamp at 1,000 lamps (est.).
9. Timeline
| Step | When |
|---|---|
| Shape and placement (this page) | done, 4 Nov 2026 |
| Rev T CAD: the board in the lamp CAD, every part checked in 3D | next |
| Schematic, footprints, routing | Dec 2026 – Jan 2027 |
| Rev A boards made and tested | Mar 2027 (est.) |
10. Still to check
- The rev T CAD changes: camera window Ø14 → Ø17, eye-distance window 8 × 10 → 11 × 12, a Ø3 mic port with a membrane, the call-light strip thinned to 2 mm, a 5.5 mm tamper boss, and the ballast plate moved forward of the column so the base board has its place (which also moves the centre of mass to the child’s side).
- The camera chip’s package drawing (est. 10.6 × 9.2) and the M12 holder’s height with the lens focused at 450 mm.
- Wi-Fi range from inside the steel head (antenna radiates through the opal cover).
- The reading light’s blue-light and flicker tests, and the arm’s touch temperature.
- The tail’s length and copper weight for 3 A with the flex maker.
Sources
- Rockchip RV1126B and the Forlinx FET1126Bx-S module data: https://www.forlinx.net/product/rv1126b-som-185.html
- Sony IMX415 (8.46 MP, 4-lane MIPI): https://www.sony-semicon.com/en/products/is/security/security.html
- ST VL53L1X: https://www.st.com/en/imaging-and-photonics-solutions/vl53l1x.html
- Vishay VEML7700: https://www.vishay.com/en/product/84286/
- Infineon IM69D130: https://www.infineon.com/cms/en/product/sensor/mems-microphones/mems-microphones-for-consumer/im69d130/
- Analog Devices MAX98357A: https://www.analog.com/en/products/max98357a.html
- Microchip ATECC608B: https://www.microchip.com/en-us/product/atecc608b
- Omron D2F: https://omronfs.omron.com/en_US/ecb/products/pdf/en-d2f.pdf
- Samsung LM281B+ mid-power LED: https://www.samsung.com/led/lighting/mid-power-leds/2835-leds/lm281bplus/
- IEC 60598-2-10 (portable luminaires for children): https://webstore.iec.ch/en/publication/1386
- IEC 62471 (photobiological safety of lamps): https://webstore.iec.ch/en/publication/7076
- The lamp: products/studyone/cad/studyone-cad.mjs (rev A); the board: products/studyone/hardware/pcb/studyone-board.mjs
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. StudyOne’s board was made with every rule from the start: 15 pass, 5 fixed, 9 to prove, 0 fail. The full review, with every number and its source, is on the board page. It shows:
- Page camera pixels: a 4 mm handwritten digit at the farthest page corner fills about 20 px against a 15 px need; a 3 mm spelling letter at the page centre about 16 px against 12. The 8 MP camera chip at 5 fps uses 12 % of its link.
- Two windows grow (fixed): our camera chip sits on the head board under a lens holder, so the camera window grows from Ø14 to Ø17; the eye-distance chip is on a tab folded out of the board, so its window grows from 8 × 10 to 11 × 12. Both are rev T CAD changes.
- The child’s head in view: both too-close calls (head 25 cm and 18 cm over the page) are inside the eye-distance chip’s 27° cone, 4.3° and 10.2° off its axis.
- The latched microSD (J1) is fitted, and our software starts from it; updates run only when the lamp is off.
- Conformal coating against a spilt drink is asked for in the quote.
- Fast lines on a solid ground plane (to prove, lesson: planes, from the CricketOne test-board layout of 4 Nov 2026): RV1126B memory; 1 camera MIPI link (100 Ω pairs); 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.
- To prove on rev A: the AI time per answer, Wi-Fi from inside the steel head, the reading light’s blue-light and flicker tests, the arm’s touch temperature, the tamper boss, and the tail down the column.
The request for quote is /build/studyone-quote.
New shared rule (4 Nov 2026, from the CricketOne test-board circuit): the Wi-Fi module’s own clock. Drawing CricketOne’s circuit pin by pin found that the AP6256 Wi-Fi/Bluetooth module runs from a 37.4 MHz reference clock, which our board notes had as 26 MHz or left out. Every board with an AP6256 is now checked for a 37.4 MHz clock beside it (MEMS where the product takes knocks). On this board the AP6256 had no clock of its own on the board; Y3, a 37.4 MHz MEMS oscillator, now sits next to it on side B. The review shows it under Radio (lesson: wificlock).