AN2446 application note, introduces the features and functions of STEVAL-IHT002V1 intelligent thermostat. This thermostat is based on ST7Ultralite MCU, it can drive the compressor, replace PTC and directly drive the start winding. Stall rotor detection is also implemented. Both functions are oriented to reduce the total power consumption. It can be used for small or medium compressors
This document describes the STEVAL-IHT002V1 evaluation board, a low-cost solution designed to replace mechanical thermostats in compressor-based applications. The board utilizes an 8-pin ST7Ultralite microcontroller to manage the RUN and START windings of the compressor, implement stall rotor detection, and optimize power consumption.
The application note details the circuit description, system operation including temperature regulation and dead-time management, and provides instructions for customizing both the software and hardware modifications to adapt the board to specific compressor requirements.
| MCU Type | ST7Ultralite |
|---|---|
| Internal Clock | 1 MHz |
| Flash Memory | 1 KByte |
| Temperature Range | -23 °C to +10 °C |
| Sampling Rate | 50 times per second |
| START Winding Duration | 500ms |
| Stall Rotor Monitoring Time | 5 seconds |
| AC Switch Temperature Limit | 85 °C |
| Power On Delay | 3 seconds |
It is designed to replace existing mechanical thermostats in compressor-based applications.
It monitors the temperature of the AC switch driving the RUN winding; a faster temperature increase indicates a stall.
The START winding is supplied for 500ms before being turned off.
The compressor is not turned on if the AC switch temperature exceeds 85 °C or drops below 0 °C.