Temperature and Humidity Sensor (SHT31) DevKit from Sensirion

The Sensirion SHT31 Smart Gadget Development Kit is a reference design circuit board and development kit showcasing their humidity and temperature sensors. The kit includes an LCD display for real-time humidity, temperature, and dew point readings, as well as Bluetooth Low Energy (BLE) connectivity for communication with iOS and Android smartphones.

Smart Gadget DevKit assembled with stand (included)

The Smart Gadget example app enables wireless connection to the Smart Gadget via BLE, displaying temperature and humidity values and allowing data logging. Users can customize the Smart Gadget's settings, including logging intervals and data download. The Smart Gadget can store up to 16,000 value pairs, and logging remains active even if BLE connection is lost. The kit provides flexibility in choosing displayed physical values and offers detailed instructions for usage. Additionally, users can rename the Smart Gadget, and downloaded data is unaffected by actions on the Gadget device. A push button allows for switching between dew point and relative humidity, enabling or disabling Bluetooth communications (holding >1 sec) and switching between °C and °F (via a removal and insertion of the battery).

Layout and Block Diagram

DevKit Layout

SHT31 Smart Gadget Block Diagram

Specifications

• Temperature and Humidity Sensor: SHT31
• Humidity
• Typ. relative humidity accuracy : ±2 %RH (Relative Humidity)
• Operating relative humidity range : 0 - 100 %RH
• Response time (τ63%) : 8 s  
• Temperature
• Typ. temperature accuracy ±0.2 °C
• Operating temperature range -40 - 125
• Response time (τ63%) : > 2 s
• Microcontrollers:
• Braveridge BVMCN5103-BK (Bluetooth stack and main firmware)
• nRF51822 based module
• Freescale MC9S08LL8CGT (used mainly for driving LCD)
• 8-bit MCU, S08 core, 8KB Flash, 20MHz, QFN 48
• Display: LCD for humidity, temperature and dew point in °C and °F
• Power: 2.4 - 5.5V - CR2032 Battery
• Operating Temperature range: -10 to 60 °C
• 16'000 value pairs (RH and T) which corresponds to a duration of 4.5 hours for 1 second logging interval and 5.5 years for 3 hours logging interval (FIFO/Circular Storage Strategy)
• 16k data point download to mobile - approximately 10 minutes
• Recommended for indoor operation only

Contents

Included in the box are the SHT31 based Smart Gadget board itself, a pcb stand and some getting started instructions.

Included in the box

Assembling the PCB stand for the DevKit

Further Information

Developers can access complete design resources on Sensirion's GitHub page, covering hardware design, firmware for BLE module and LCD driver, and software code for iOS and Android example apps. For evaluation purposes, Keil uVision (4 or 5) is recommended as the development environment, with the project consuming around 30kB of flash the free 32kB licence of Keil is said to be sufficient. Further, a debugger for Cortex M0 Devices would be required (examples include j-Link, j-Link Lite, ULINK2 etc).

At time of writing the development kit was priced at around $30 (USD) and available from either Digikey or Mouser.

In order to work with the Smart Gadget, a smartphone or tablet needs to be Bluetooth 4.0 compatible. This is the case for the majority of Android devices starting from approximately generation 2013 and newer, Apple iPhones generation 4S and newer, and Apple iPad generation 3 and newer.