Temperature and Humidity Sensor Node Design

esdrufao

esdrufao

Make me a temperature and humidity sensor node with Wifi and Bluetooth, powered by USB-C (5V) for consumer use.
It should be a low-power environmental node with a digital T/RH sensor, ultra-low-power MCU with Wi-Fi + Bluetooth (dual-radio) — 2.4 GHz 802.11 b/g/n plus BLE 5.x powered by USB-C (5 V) — USB-C receptacle 5 V default; include reverse/OVP/UVLO/OCP protection and plan for 0.5–3 A sources.

flux

I've made a plan, and started work on it.
Add ESD protection
Prefer SHTC3 sensor
Place antenna at edge
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Execution Plan
Project
Low-power consumer temperature and humidity sensor node with:
  • Digital temperature / relative humidity sensor
  • Ultra-low-power MCU with integrated 2.4 GHz Wi-Fi 802.11 b/g/n and BLE 5.x
  • USB-C 5 V default-source input
  • Input protection covering reverse polarity, over-voltage, under-voltage lockout, and over-current protection
  • Compatibility target: USB-C sources from 0.5 A to 3 A
High-Level Plan
1. Capture requirements and operating assumptions
  • Define the product-level goals: sensing interval, battery/no-battery assumption, always-on vs duty-cycled operation, wireless update/reporting behavior, and expected consumer environment.
  • Lock key electrical requirements for the USB-C input path: 5 V only, default USB-C sink behavior, acceptable input range, startup behavior, allowable peak/average current, and fault-handling expectations.
  • Define sensing and wireless performance requirements: temperature/RH accuracy, response time, BLE/Wi-Fi use cases, provisioning method, antenna/enclosure constraints, and low-power targets.
  • Capture review criteria early: power budget target, protection coverage, BOM availability, and manufacturability goals.
2. Build the system architecture
  • Partition the design into major blocks: USB-C power entry, input protection, 3.3 V regulation/power management, MCU + RF, digital T/RH sensor, programming/debug, and optional status/user interface.
  • Choose the USB-C sink strategy for 5 V default-source operation, including CC implementation and clear assumptions for interoperability with 0.5 A to 3 A sources.
  • Define the protection chain architecture: ESD/TVS at connector, reverse-blocking strategy, over-voltage protection stage, UVLO behavior, and current limiting / over-current protection.
  • Select the power tree and low-power strategy: regulator topology, sleep-state current goals, sensor power domain strategy, and any measurement or test hooks needed for current validation.
3. Implement the schematic in functional blocks
  • Create the USB-C receptacle and input-power front end first, including CC resistors, protection devices, filtering, and the regulated system rail.
  • Add the MCU subsystem with clocks, boot/configuration, decoupling, RF/antenna support, programming/debug access, and any required reset or enable circuitry.
  • Add the digital temperature/humidity sensor, its interface to the MCU, required pull-ups/decoupling, and placement-aware design notes for later PCB work.
  • Add system support circuitry such as indicators, test points, current-measurement options, and connectors only if they align with the low-power requirements.
4. Review, validate, and prepare for layout
  • Run schematic/ERC reviews focused on power integrity, missing support parts, pull-ups, decoupling, and proper handling of unused pins.
  • Review the protection strategy against the intended USB-C use cases: normal 5 V operation, source current range from 0.5 A to 3 A, reverse/incorrect input conditions, over-voltage events, UVLO behavior, and over-current response.
  • Check the design against low-power intent: sleep-capable rails, leakage paths, regulator quiescent current, sensor standby behavior, and MCU wake/report cycle assumptions.
  • Finish with a layout-readiness review covering RF antenna constraints, connector placement, power-entry current paths, grounding/decoupling strategy, and sourcing risk for critical parts.

    Project

    High-Level Plan

    1. Capture requirements and operating assumptions

    2. Build the system architecture

    3. Implement the schematic in functional blocks

    4. Review, validate, and prepare for layout

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