Hardware
Bill of materials
Every part, with a source and a price. $849 as priced in November 2026; most prices are estimates, the two marked verified were checked at the vendor.
Prices are US dollars from common suppliers (Adafruit, Amazon, AliExpress, lab-supply houses). The two items marked verified were checked at the vendor in Nov 2026; everything else is an estimate — expect ±15 %. The CSV source is hardware/analyzer/cad/bom.csv.
Compute
| Item |
Qty |
Unit |
Ext. |
Source / part |
Notes |
| Raspberry Pi 4 Model B 2 GB |
1 |
$45 |
$45 |
Raspberry Pi reseller |
Pi Zero 2 W also works (slower dashboard) |
| microSD 32 GB A2 |
1 |
$8 |
$8 |
any |
Raspberry Pi OS Lite 64-bit |
| 12 V 5 A power supply (barrel) |
1 |
$14 |
$14 |
Mean Well GST60A12 or similar |
fused |
| 5 V 3 A buck converter module |
1 |
$4 |
$4 |
MP1584 / LM2596 |
feeds Pi 5 V pin |
| MCP23017 breakout |
1 |
$6 |
$6 |
Adafruit 5346 |
I2C 0x20 |
| 8-channel low-side MOSFET module |
1 |
$10 |
$10 |
IRF520/IRLZ44N board |
12 V pumps + stirrers |
| TMC2209 StepStick driver |
5 |
$4 |
$20 |
BTT/Fysetc |
1/16 microstep; VREF 0.6 V |
| 1-ch 5 V relay module |
1 |
$3 |
$3 |
any |
dry contact to Hydros Sense port |
| Perfboard 9x15 cm + headers + screw terminals + JST-XH kit + wire |
1 |
$25 |
$25 |
any |
stepper carrier board |
| DS18B20 waterproof probe |
1 |
$3 |
$3 |
any |
+ 4.7 k resistor |
| Water leak sensor module |
1 |
$4 |
$4 |
any |
drip tray |
| Float switch (waste bottle) |
1 |
$4 |
$4 |
any |
NC/NO selectable |
Sensing
| Item |
Qty |
Unit |
Ext. |
Source / part |
Notes |
| Atlas Scientific pH Kit KIT-101P (EZO-pH + lab-grade probe + isolated carrier + buffers) |
1 |
$167 |
$167 |
atlas-scientific.com |
verified Nov 2026 |
| Adafruit AS7341 10-channel spectral sensor |
1 |
$16 |
$16 |
Adafruit 4698 |
I2C 0x39 |
| LEDs: 5 mm white high-CRI, 5 mm 850 nm IR, resistors, 2N7002 |
1 |
$4 |
$4 |
any |
|
Fluidics
| Item |
Qty |
Unit |
Ext. |
Source / part |
Notes |
| NEMA17 stepper 34 mm (17HS4023) |
5 |
$9 |
$45 |
any |
0.7-1.0 A |
| T8x2 lead screw 150 mm + brass nut |
5 |
$5 |
$25 |
any |
2 mm lead (single start) |
| 5 mm to 8 mm flexible coupler |
5 |
$1.6 |
$8 |
any |
|
| 8 mm smooth rod 120 mm + LM8UU |
5 |
$3 |
$15 |
any |
|
| 5 mL glass luer-lock syringe |
5 |
$6 |
$30 |
Fortuna Optima / Socorex |
PP Norm-Ject acceptable for reagents |
| Luer one-way check valve (PP/silicone) |
10 |
$2 |
$20 |
Qosina / Cole-Parmer |
2 per pump |
| Micro limit switch |
5 |
$0.8 |
$4 |
any |
home switch |
| 12 V peristaltic pump with silicone tube |
6 |
$12 |
$72 |
Kamoer KPHM100 or generic |
1-1.5 mL/s |
| 40 mm 12 V fan + N52 8x3 magnets + PTFE stir bars (25 mm & 8 mm) |
2 |
$6 |
$12 |
any |
magnetic stirrers |
| Silicone tubing 2x4 mm 5 m |
1 |
$8 |
$8 |
any |
pump + sample lines |
| PTFE tubing 1/16 ID x 1/8 OD 5 m |
1 |
$12 |
$12 |
any |
acid + reagent lines |
| Luer barbs / 1/8 barbs / Y / plug fitting kit |
1 |
$12 |
$12 |
any |
|
| Inline 100 um sample filter |
1 |
$6 |
$6 |
any |
on intake |
| 60 mL borosilicate vial 40x100 mm (Cell A) |
1 |
$6 |
$6 |
any |
|
| Hanna HI731331 22 mm glass cuvettes (4 pk) (Cell B) |
1 |
$12 |
$12 |
Hanna |
|
| 2 L HDPE waste bottle + 500 mL HDPE acid bottle |
1 |
$12 |
$12 |
any |
Trident NP waste requires HDPE/glass |
| Bottle caps with 2 ports + tube weights |
6 |
$1.5 |
$9 |
any |
|
Enclosure
| Item |
Qty |
Unit |
Ext. |
Source / part |
Notes |
| Cast acrylic 3 mm 600x900 mm |
2 |
$20 |
$40 |
any |
sides/top/front/bulkhead/shelves |
| Cast acrylic 6 mm 300x600 mm |
1 |
$18 |
$18 |
any |
base/back/bottle tray |
| M3 hardware (incl. 40× M3×12 + nuts for T-slots) + heat-set inserts + hinges + magnets + grommets |
1 |
$20 |
$20 |
any |
|
| PETG filament (~500 g) |
1 |
$12 |
$12 |
any |
pumps/caps/holder/brackets |
Chemistry
| Item |
Qty |
Unit |
Ext. |
Source / part |
Notes |
| Neptune Trident NP 2-month reagent kit |
1 |
$60 |
$60 |
BRS / Saltwater Aquarium |
60 tests each; ground ship only |
| 0.1 N HCl certified 1 L |
1 |
$15 |
$15 |
Hach/LabChem/Ricca |
dilute 1:5 |
| Na2CO3 ACS primary standard 100 g |
1 |
$14 |
$14 |
any |
alkalinity reference |
| KNO3 ACS + KH2PO4 ACS (standards) |
1 |
$24 |
$24 |
any |
|
| DI water 4 L |
1 |
$5 |
$5 |
store |
|
Totals
| Section |
USD |
| Compute |
$146 |
| Sensing |
$187 |
| Fluidics |
$308 |
| Enclosure |
$90 |
| Chemistry |
$118 |
| Total |
$849 |
Not included: a 3D printer and laser-cutter time, DI water on an ongoing basis, and a Hydros controller if you want that integration. Budget about $35/month for consumables at the default schedule (Trident NP kit $60/2 months, acid, standards).
Substitutions that keep the price down
- Raspberry Pi Zero 2 W instead of the Pi 4 saves $30; the dashboard is slower but the analyzer is unaffected (pigpio works on both).
- Plastic Norm-Ject syringes (PP/PE, no rubber) instead of glass save $22; replace them yearly.
- Skip the Atlas lab-grade probe and use a $25 generic BNC electrode with the EZO circuit: Gran titration tolerates a mediocre electrode better than a pH monitor does, but expect to replace it every 6–9 months.
- Three syringe pumps instead of five if you use lab-mixed reagents (one acid + one reagent per test) saves $70.
Substitutions that are not worth it
- Peristaltic pumps for reagent dosing: tube wear changes volume per revolution by several percent within weeks.
- A single photodiode instead of the AS7341: you lose the secondary-wavelength check and the reagent characterisation mode for $8.
- Open-bottle reagents without check valves: siphoning and air ingestion will ruin the dosing accuracy.