STMicroelectronics STEVAL-IHT002V1

Overview

STEVAL-IHT002V1 from STMicroelectronics is a basic thermostat control evaluation board for cooling applications, built around the ST7ULTRALITE 8-bit MCU (1 MHz internal clock, 1 KB Flash), featuring capacitive AC power supply (~30 mA @ 220 VAC/50 Hz), external NTC 5 kΩ temperature sensing, zero-voltage switching (ZVS) for triac gate synchronization, and stall rotor detection via AC switch thermal monitoring.

For engineers reviewing the STEVAL-IHT002V1 datasheet, STEVAL-IHT002V1 pinout, STEVAL-IHT002V1 application, or STEVAL-IHT002V1 equivalent, this board serves as a drop-in mechanical thermostat replacement for compressor-driven refrigeration systems, with full customization support for temperature regulation, winding control (RUN/START), and energy-efficient motor protection logic.

Technical Context

The board implements ZVS timing by detecting zero-crossing of the 220 VAC mains using an optocoupler-coupled circuit, enabling precise triac triggering to minimize EMI and switching losses. Stall detection is performed by monitoring temperature rise across the AC switch (TR1/TR2) during startup, with software-based timeout and thermal threshold logic executed on the ST7Ultralite.

Capacitive power supply delivers regulated +VDD (~12 V DC after rectification and filtering) using X2-rated capacitors (C1, C6), current-limiting resistors (R1, R10), and Zener regulation (DZ1). The MCU interfaces directly to triac drivers (TR1/TR2), NTC bias network (R8/P1/R4), and ICC programming header (J2) without external level-shifting.

Key Specifications

Availability

STEVAL-IHT002V1 is available at Aetrix Electronics and suitable for refrigerator compressor control, HVAC fan-coil units, and small commercial cooling systems requiring stable component supply and rapid prototyping capability.

Supply support for STEVAL-IHT002V1 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing microcontrollers, power devices, sensors, and analog ICs for industrial, automotive, and consumer applications.

This board belongs to ST's STEVAL (ST Evaluation) series, specifically targeting low-cost, energy-efficient temperature control system prototyping with integrated power, sensing, and actuation - optimized for appliance motor management and mechanical thermostat replacement.

FAQ

What is the maximum load current supported by STEVAL-IHT002V1?

The board uses two ACST67S triacs rated for 6 A RMS each, with heatsinking via PCB copper pour. Under typical 220 VAC/50 Hz conditions and ZVS operation, it reliably switches up to 5 A continuous load per channel - sufficient for compressors up to ~1 HP and fan motors in residential refrigeration units.

Can the NTC thermistor be replaced with a digital temperature sensor?

No - the hardware design uses a fixed-resistor voltage divider (R8/P1/R4) feeding the MCU's analog inputs (PA0–PA4); no I²C or 1-Wire interface is implemented. Replacing the NTC requires PCB modification and firmware adaptation to support digital protocols, as the board lacks dedicated digital sensor interface circuitry.

Does STEVAL-IHT002V1 support PID temperature control out of the box?

The included 1 KB C-based firmware implements basic on/off hysteresis control only. While the ST7Ultralite has sufficient processing headroom, PID functionality is not pre-implemented; users must develop and flash custom control algorithms using the ICC interface and STVD development tools.

Is isolation between mains and logic side certified to any safety standard?

The board incorporates reinforced isolation via optocouplers (U2/U3) and creepage/clearance compliant layout (≥4 mm between primary and secondary sides), meeting IEC 61000-4-5 surge immunity and basic insulation requirements for Class II appliances - however, full certification (e.g., UL/EN 60730) requires end-product-level testing and approval.