Description
The STEVAL-IHT001V2 thermostat kit provides a robust and low-cost ST solution (microcontroller and AC switches) to control refrigerators, freezers or fridge/freezer combinations. Basic, defrost, and air circulation versions are configurable in order to address the low-end and medium-end cooling appliances market. It allows the control of a single-phase induction motor and a light bulb, and optionally, a defrost resistor and a fan, working on 220/240 VRMS, 50/60 Hz mains voltage. The thermostat kit is operational with 100/120 V RMS 50/60 Hz but the supply capacitor value must be modified. The board can operate in an ambient temperature range from 0 °C to 60 °C. The exact maximum temperature depends on the power of the loads. For demonstrative purposes a graphic user interface (GUI) has been developed. The connection between the PC and STM8S microcontroller, the MCU performing thermostat regulation, is achieved through a USB bus. As the STM8S is a low-cost MCU without an embedded USB peripheral, an additional MCU (STM32) has been used as a bridge between the PC and STM8S MCU, for demonstrative purposes only.

Features
■ Low-cost solution for spark-free thermostats: – No need for a sealed version – Low-cost STM8S microcontroller for thermostat control – Low-cost capacitive power supply
■ High efficiency: – Refrigerator consumption reduction by adjusting and reducing the hysteresis threshold of the temperature – Improved efficiency by turning on the defrost resistor only when it's useful and not at each OFF cycle of the compressor (as done in some mechanical thermostats)
■ High system immunity: – Overvoltage protected ACS switches: ACST610-8FP for compressor control, ACS110-7SN for defrost resistor and ACS102-6TA for light bulb and fan – Class A criteria for IEC 61000-4-4 up to above 3 kV levels
■ Flexibility: – Development: program setting with PC interface to change firmware variables – Industrialization: end-of-production MCU programming thanks to FLASH, for soft upgrade and efficient MCU stock management
■ RoHS compliant