JLCPCB PCBA
walkthrough.

JLCPCB occupies a specific sweet spot for projects like this one. For a two-layer board with surface-mount components and modest volumes — anywhere from 5 to 500 units — there is no other fabrication-plus-assembly house that comes close on cost-per-finished-board. Bare-PCB-only options in India and China can be cheaper per unit, but bare PCBs do not solve the actual constraint, which is hand-placing 80+ small parts without reflow equipment.

The v4 carrier board ships from JLCPCB as a fully assembled board with everything but five through-hole connectors populated. The through-hole parts (terminal block, DC barrel jack, USB-A, two tactile switches, screw terminal block) are hand-soldered after delivery because JLCPCB charges a premium for through-hole assembly that is not worth it at this volume. Total turn-around from order placement to delivered boards is typically 10–14 days to most countries.

For a turn-key assembly order, JLCPCB needs three files. They are all in the Sankhya-v4.zip download:

• Gerber zip — the manufacturing files for the bare board. Inside the outer zip there is an inner Gerber_V4-ESP32_PCB_V4-ESP32_*.zip. Upload the inner zip, not the outer one. JLCPCB's DFM checker will reject the outer zip with a confusing error.
• BOM (Bill of Materials) — a CSV listing every component, its quantity, its reference designators, and its LCSC part number. JLCPCB's assembly service draws components from LCSC's catalogue, so every entry must have a valid LCSC part number — not a generic part name, not a Mouser part number.
• Pick and Place (CPL) — a CSV listing the XY coordinates, rotation, and side (top or bottom) for every component the assembly line will place. This is what tells the pick-and-place machine where each part goes.

All three files in the v4 download are pre-validated. JLCPCB's DFM checker should report zero errors on the v4 board. If it reports any, stop and re-download — the file format is sensitive to whitespace and column ordering that some text editors silently mangle.

Go to jlcpcb.com and click Quote Now. Drag the inner Gerber zip onto the upload area. JLCPCB will auto-detect the board dimensions — for the v4 board, this is 60 mm × 80 mm.

Set the following parameters explicitly:

• Layers — 2. (The v4 board is intentionally two-layer to keep cost low.)
• Material — FR-4. (Default.)
• Thickness — 1.6 mm. (Default.)
• Surface finish — ENIG (gold). Not HASL. HASL is cheaper but leaves uneven pads that cause assembly defects on fine-pitch parts like the ESP32-S3 module's castellations. ENIG adds roughly $5–8 per order — pay it.
• Soldermask — green. (Any colour works; green is fastest and cheapest.)
• Silkscreen — white. (Default.)
• Quantity — 5 is the minimum. 10 is the common sweet spot — only marginally more expensive, gives you spares and a chance to test variations.

Leave everything else at defaults. Specifically, do not enable Castellated holes, Edge plating, or Impedance control — none of them apply to this board.

Scroll down on the quote page and toggle PCB Assembly on. Select:

• Assembly side — Both sides. (The ESP32-S3 module sits on the bottom side; everything else is top.)
• Tooling holes — Added by JLCPCB. (Default.)
• Confirm parts placement — Yes. (Free service; lets a JLCPCB engineer flag any obvious BOM-PnP-Gerber mismatch before the line starts.)
• PCBA Qty — match the PCB quantity, or set to the number of boards you actually want assembled. Some people order 10 bare PCBs but only have 5 assembled, to keep spares in case of revisions.

Click Next. JLCPCB will prompt you to upload the BOM and the CPL (Pick and Place). Upload BOM_V4.csv and PickAndPlace_V4.csv respectively. JLCPCB's online tool will parse them and show you a preview of every part it intends to populate, with a placement preview overlaid on the board outline.

Review the preview carefully. The two failure modes to look for are parts rotated 180° (compare the PnP rotation against the silkscreen orientation marker) and parts marked Do Not Place that should be placed. If anything looks wrong, stop and contact JLCPCB support — do not push through and hope.

JLCPCB will show a final order page with:

• PCB cost per piece
• PCB assembly setup fee (one-off, around $8–12)
• Stencil fee (required for assembly, around $8–10)
• Component cost per board
• Shipping (DHL Express to most countries is 4–7 days; standard shipping is 10–14 days)

For ten fully assembled boards, the total typically lands in the $150–220 range delivered, depending on shipping mode. The dominant variable is shipping; the boards themselves are roughly $8–10 each in the 10-piece quantity.

Pay with card. JLCPCB will email you when the order enters production, when it ships, and when it clears customs in your destination country. The whole pipeline is well-instrumented and rarely surprises you.

When the boards arrive, every SMT component is already populated. You will need to hand-solder the through-hole parts: the screw terminal block for the 12V input, the DC barrel jack, the USB-A connector for the 4G dongle, and the two tactile switches (BOOT and RESET).

Three notes on hand-soldering these:

The screw terminal block has 3.81 mm pitch; the through-holes are sized for it. Buy a Phoenix-style block from the same supplier as the rest of the BOM — not a 3.5 mm or 5.08 mm block, both of which look similar at a glance and will not fit. The exact part number is in the BOM.

The DC barrel jack is 5.5 mm OD, 2.1 mm ID. Earlier prototypes had a mismatch in the BOM (5.5/2.5 instead of 5.5/2.1) which made the boards incompatible with the standard cell pack pigtail. The v4 BOM has been corrected. Double-check the part you order matches.

The USB-A port is a standard right-angle through-hole connector. Make sure the four signal pins are fully wetted; the two large mechanical tabs can be lightly tacked.

The ESP32-S3 module ships from JLCPCB with no firmware. The carrier board exposes USB-C for programming — plug a USB-C cable from your computer into the USB-C jack on the board.

From the Arduino IDE, select board ESP32S3 Dev Module, set USB CDC On Boot to Enabled, set Flash Size to 16 MB, and set PSRAM to OPI PSRAM (the DOIT module uses octal-SPI PSRAM, not the more common quad-SPI). Hold the BOOT button on the carrier board, briefly tap RESET, then release BOOT — this puts the module into download mode. Upload the firmware.

After upload, tap RESET once and the module boots into the application. The first-boot serial output should announce the node identity (resolved from its MAC address against the server-side node registry) and attempt a WiFi connection.

A browser-based flash tool that uses the Web Serial API is in development at flash.sankhyafarms.com — that will eventually remove the Arduino IDE step entirely.

For someone ordering this board for the first time from JLCPCB, in the 10-piece quantity, with ENIG finish and full PCBA, delivered DHL Express to India or most of Asia:

That works out to roughly $14–17 per fully-assembled-and-shipped board. The cell pack, solar panel, enclosure, and external antenna are additional — figure another $35–45 per node for those. All-in deployed cost per orchard sensor node settles in the $50–60 range at this volume; it falls below $40 once you cross 50 units per order.

For the full board specification — schematics, BOM, GPIO map, and power architecture rationale — see /open-hardware or the GitHub mirror at github.com/shsa1984/sankhya-node-hardware. For sensor wiring once the board arrives, see RS-485 Modbus soil sensor wiring. For the power-budget rationale and component-choice reasoning, see ESP32-S3 solar-powered sensor node design.