growbox / PCB · rev A · routed

Growbox I/O Board

One board between the Raspberry Pi and the four chambers, replacing the breadboards. Click a zone on the board, or a label underneath it, to see what plugs in there and what each pin carries. There's also an option with the computer on the board: the CM5 board.

190 × 140 mm 2-layer
110 parts
76 nets
fully routed
ERC / DRC 0 errors
+ 4× chamber sensor boards

Top view render of the Growbox I/O board: Pi ribbon header on the left, four chamber sensor headers along the top, 5 V barrel jack and fuse top right, LED strip headers down the right edge, actuator and heater terminals along the bottom.

board coordinates in mm, origin top-left

Perspective 3D render of the board showing box headers, screw terminals facing the board edges, and SMD parts. — 3D render. Screw terminals open toward the board edges and the barrel jack takes its plug from the right. The 5 V paths are 1.5 mm tracks plus a 5 V copper pour; ground is poured on both layers.

Power budget

Everything runs from the one barrel jack, rated 8 A. The heaters only nudge each chamber by 1–2 °C over long periods, so the software pulses them one at a time. A PTC element is either on (about 1.6 A, self-limited near 100 °C) or off, and the duty cycle sets the average heat.

heater 1.6 lights 1.5 ≈ 4.9 A left for strips

one PTC heater on at a time white lights, ~1.5 A (estimate) headroom for the strips

No board change is needed for this: same MOSFETs, terminals and 10 A fuse. Running all four heaters together would use 6.4 A of the 8, so the software should keep them staggered.

one design, four copies

Chamber sensor board

A 25.4 mm square that lies flat on each chamber floor against the wall, where the box design already reserves it. The three sensor modules plug into sockets with the pins they came with, so a faulty one swaps out without soldering. The ribbon from the main board plugs in underneath and drops straight down the notch.

Top view to scale, in mm. Dashed outlines are the modules as they sit on their 8.5 mm sockets, overhanging the board along the wall. Module sizes are typical for these boards; check yours with a ruler.

Socket	Pins, in order	On the board
COLOUR	LED INT SDA SCL 3V3 GND VIN	LED tied low (module's white LED off), VIN gets 3.3 V, INT and 3V3 unused
LUX	VCC GND SCL SDA ADDR	ADDR tied low: address 0x23
DHT22	+ SIG −	sensor faces into the chamber
RIBBON	2×5, underside	same pinout as the main board's chamber header

The light sensors sit about 10 mm up, so the dish holder's 2.4 mm plate slides underneath.
Front-wall and back-wall chambers use the same board, turned round.
Plug the ribbon either way round and nothing shorts: wires 1 and 10 are both 3.3 V.
The I2C bus will run at half speed (50 kHz) for the long ribbons: one line in the Pi's config.txt.
The box's notch plug needs a pocket for the ribbon plug; that goes in the box drawings next.

3D render of the sensor board with its three sockets and the header pins coming through from underneath. — Sockets on top, header pins coming through.

Underside of the sensor board showing the 2x5 ribbon header. — Underside: the ribbon header.

Cost, assembled by JLCPCB (AUD)

Option B on the cost page: a Raspberry Pi 5 next to this board on a ribbon cable.

Item	1 growbox	each, of 6	Notes
Board printed and assembled	A$206	A$55	2 layers, 2 oz copper. 5 printed, 2 assembled (one spare)
Chamber sensor boards ×4	A$52	A$13	5 printed and assembled; mostly JLCPCB's fixed fees
Computer: Raspberry Pi 5, 1 GB	A$70	A$70	4 GB adds about A$40
Pi 5 cooler and 32 GB microSD	A$21	A$21
Power supplies	A$50	A$50	Pi 5 27 W USB-C (A$20) + 5 V 10 A for the loads (A$30)
40-way ribbon cable	A$5	A$5
Electronics total	A$404	A$214	per growbox; shipping is on the cost page

The two board lines are real costs for these exact designs: JLCPCB's quote for the bare boards, live part prices and its published assembly fees, on 3 October 2026. The rest are typical online prices. All in Australian dollars, US prices at about A$1.52 per US$1. The whole growbox, with the box, base, cameras, lights and heaters, is on growcube.p4s.space/cost.

Where this is

Done

Schematic

Generated from circuit.py. Electrical rule check passes.

Done

Placement

Every part placed in its zone and labelled on the silkscreen, on both boards.

Done

Routing

Autorouted with Freerouting: 1.5 mm 5 V tracks, 1 mm load tracks, ground on both layers. Design rule check: 0 errors.

Done

Order files

Gerbers, bill of materials and placement file for JLCPCB, for both boards, every part matched to a stocked LCSC number.