IoT PCB Design

J

juan1087

Design a PCB for an IoT environmental monitoring node controlled
by a Heltec WiFi LoRa 32 V3 mounted on 2.54mm female pin headers.
POWER SYSTEM:
  • DC barrel jack 5.5mm (5V input)
  • TP4056 charger module on pin headers
  • Two JST PH 2.0 connectors for 3.7V LiPo batteries in parallel,
    each with 1N5817 Schottky diode on positive line
  • AMS1117-3.3 (SOT-223) with 10uF and 100nF caps on input/output
  • 5V rail: DC jack to MQ-137 connector and Heltec 5V pin
  • 3.3V rail: AMS1117 to SHT41 connector
  • 3.7V rail: TP4056 BAT+ to Heltec 3V7 pin
SENSOR CONNECTORS (Molex 4-pin 2.54mm):
Connector 1 - SHT41:
Pin 1: GND | Pin 2: 3.3V | Pin 3: SDA->GPIO17 | Pin 4: SCL->GPIO18
Connector 2 - MQ-137:
Pin 1: GND | Pin 2: 5V | Pin 3: AOUT->GPIO2 | Pin 4: DOUT->GPIO3
PCB REQUIREMENTS:
  • Size: 70mm x 50mm
  • 4 mounting holes M3 in corners
  • Ground plane on bottom layer
  • Heltec USB-C port accessible on board edge
  • Trace width: 0.5mm signal, 1.5mm power
  • Silkscreen labels on all connectors

flux

No PCB changes were made because no ACUs are currently available for design execution.
Remaining work:
  • Resolve power-path safety: avoid powering the Heltec’s 5V and 3V7 pins simultaneously, and confirm the TP4056 module includes battery protection.
  • Confirm the two parallel LiPo cells are matched; the proposed series diodes prevent true parallel charging and require a clarified topology.
  • Capture the schematic, verify Heltec V3 header pinout, assign footprints, and run ERC.
  • Create the 70 × 50 mm PCB, M3 holes, edge-accessible USB-C placement, bottom GND plane, specified trace widths, routing, labels, and final DRC.
Clarify power-path
Check Heltec pinout
Add footprints
Set up board
Wire schematic

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