Build it yourself
Build one
yourself.
Everything to build one prototype collar: breakout boards, a bought strap, and parts you print. It's the same collar as the assembled one, as close to V1 as breakout boards allow, and the list will change as the design does.
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Stock and prices checked on vendor pages on . Shipping and tax not included.
| Part | Vendor | Qty | Each | Line |
|---|---|---|---|---|
| GNSS | ||||
| SparkFun MAX-M10S breakout (Qwiic)GPS, Galileo, BeiDou and GLONASS. SMA connector, powers active antennas. | DigiKey18037 | Quantity 1 | Each $45.95 | $45.95 |
| Active GPS antenna, 28 dB, SMAReference antenna for side-by-side tests. | Adafruit960 | Quantity 1 | Each $21.50 | $21.50 |
| SMA to U.FL adapterLets a small U.FL patch run on the M10S. | Adafruit851 | Quantity 1 | Each $3.95 | $3.95 |
| Subtotal | $71.40 | |||
| Motion and charger | ||||
| ISM330DHCX 6-DoF IMU (STEMMA QT / Qwiic)Industrial grade, −40 to 105 °C. | Adafruit4502 | Quantity 1 | Each $19.95 | $19.95 |
| Universal USB / DC / Solar charger, bq24074Charges Li-ion to 4.2 V, fixed in hardware. Takes 6 V panels directly. | Adafruit4755 | Quantity 1 | Each $14.95 | $14.95 |
| 10K NTC thermistorStops charging when the pack is too hot or too cold. | Adafruit372 | Quantity 1 | Each $4.00 | $4.00 |
| Subtotal | $38.90 | |||
| Battery and solar | ||||
| Lithium-ion pack 3.7 V 6600 mAhBuilt-in protection circuit. JST-PH plug fits the charger. | Adafruit353 | Quantity 1 | Each $24.50 | $24.50 |
| Voltaic 1.2 W 6 V ETFE panel, 66 × 113 mmOne each side of the GNSS antenna. | VoltaicP124 | Quantity 2 | Each $14.00 | $28.00 |
| Subtotal | $52.50 | |||
| Strap, shell and wiring | ||||
| 48" cow neck strap, 1-3/4" double-thick nylonNickel buckle. Any standard cattle neck strap works. | Heritage Animal Health— | Quantity 1 | Each $23.10 | $23.10 |
| M3 stainless screw assortment304 stainless. | AmazonB0GHMM79M9 | Quantity 1 | Each $8.99 | $8.99 |
| M3 × 4 brass heat-set inserts (50) | Adafruit4255 | Quantity 1 | Each $5.95 | $5.95 |
| 2 mm silicone O-ring cordGlue into rings to seal the lid. | AmazonB00QVB0ZG6 | Quantity 1 | Each $15.39 | $15.39 |
| M6 screw-in ePTFE ventStops pressure changes pumping water past the seal. | DigiKeyVENT-PS2NGY-O8001 | Quantity 1 | Each $3.31 | $3.31 |
| 1.25 mm 2-pin connector leads (30 pairs)Pack to the nRF9151 kit's battery socket. | AmazonB013JRWCBU | Quantity 1 | Each $6.99 | $6.99 |
| 22 AWG silicone wire kit | AmazonB07G2JWYDW | Quantity 1 | Each $15.99 | $15.99 |
| Adhesive-lined heat shrink kitSealed joints outdoors. | AmazonB0BVVMCY86 | Quantity 1 | Each $13.99 | $13.99 |
| STEMMA QT / Qwiic cable, 100 mm | Adafruit4210 | Quantity 2 | Each $0.95 | $1.90 |
| STEMMA QT / Qwiic to female sockets, 150 mmQwiic boards to the kit's header pins. | Adafruit4397 | Quantity 2 | Each $1.25 | $2.50 |
| LTE-M SIMFree pilot SIM with code FREEPILOTSIM. | Hologram— | Quantity 1 | Each $0.00 | $0.00 |
| Subtotal | $98.11 | |||
| Wired-strap harness (optional) | ||||
| M8 4-pin cordset, 0.6 m, drag-chain ratedOnly needed for powered bay modules. | DigiKey1682155 | Quantity 1 | Each $24.94 | $24.94 |
| M8 4-pin female panel socket, IP67 | DigiKeyCDM803-04A-FP-R805-67 | Quantity 1 | Each $9.50 | $9.50 |
| M8 4-pin male panel socket, IP67 | DigiKeyCDM804-04A-MP-R805-67 | Quantity 1 | Each $7.57 | $7.57 |
| Subtotal | $42.01 | |||
| Camera module (optional) | ||||
| GoPro HEROAny action camera with the two-prong mount fits. | AmazonB0DCLRRHSP | Quantity 1 | Each $204.00 | $204.00 |
| SanDisk High Endurance 128 GB microSD | AmazonB07NY23WBG | Quantity 1 | Each $36.99 | $36.99 |
| Anker 10,000 mAh USB-C power bankPass-through charging. Its mass is the counterweight. | AmazonB0CZ9M6X8Q | Quantity 1 | Each $29.99 | $29.99 |
| GoPro buckle base mount kit | AmazonB0B9X92VD2 | Quantity 1 | Each $9.99 | $9.99 |
| Right-angle USB-C cable, 1 ft (2) | AmazonB07H96FWY9 | Quantity 1 | Each $7.96 | $7.96 |
| Subtotal | $288.93 | |||
| Collar | $260.91 | |||
| Wired-strap harness | $42.01 | |||
| Camera module | $288.93 | |||
Also on the bench.
The list above assumes you already have the brain and a few basics, which the first prototype was built on:
- An nRF9151 development kit, the processor and LTE-M modem
- An LTE antenna for it
- A Qwiic buzzer for the audio cue
- About 500 g of steel for the ballast, from a hardware store
- Jumper wires, a soldering iron, and a printer or a print service
Print it in ASA, not PLA.
Buy the strap, print the rest. The top unit and the bay cradle clamp to any standard 50 mm cattle neck strap.
| Top unit shell and lid | ASA on a desktop printer, or PA12 from an MJF or SLS service |
|---|---|
| Bay cradle and module shells | ASA or PA12 |
| Strap clamps, bumpers, clips | TPU 95A |
| Seals | bought silicone O-ring, never printed |
PLA softens around 55–60 °C, and a collar in July sun gets hotter than that. PETG yellows and weakens in UV over a season. Print in a light colour: a dark shell runs much hotter, and lithium cells are happiest below about 45 °C.
Walls of 2.5–3 mm with ribs, 40 % infill or more where it carries load and solid around screw bosses and strap slots, brass heat-set inserts for any screw opened more than once.
The battery. Nothing to configure.
Every charger in this build defaults to 4.2 V, which is what lithium-ion cells expect, and the limit is set in hardware. The pack has its own protection circuit, and the thermistor stops charging when the pack is too hot or too cold. A build with no firmware on it can't overcharge anything.
Wiring
Panels to the charger's solar input, the pack to the charger's battery plug, and the same pack to the nRF9151 kit's battery socket through a 1.25 mm two-pin lead. Tape the thermistor to the pack.
If a cell gets hot, swells, or smells, disconnect it and move it somewhere it can't catch anything alight.
Our assembled collars use LiFePO4 cells, which handle heat better, with charging switched off in hardware until the charge limit is set. That setup takes a configuration step we do before a collar ships, so it isn't part of this build.
Files and firmware.
The print files, board notes, firmware, and this list will live at github.com/open-pasture/opencollar as the design settles.