HECA - Heating Element Control Assemly

In this design we used precise temperature and humidity sensor from Sensirion SHT30 connected via I2C. Sensor is equipped with ALERT output. This output is connected to N-channel MOSFET and controls PTC Heating Element. Huge advantage of this design is ALERT logic which can be programmed via I2C and it’s independent from main micro controller. In other words apart of sensor initialization it doesn’t require any action from main micro controller.

Usage

• PTC Heating element connect to connector marked as PTC HE (from SHT30 side)
• I2C cable connect to SCL, SDA, 3V3 and GND
• Heating element power supply connect to PTC and GND. PTC is positive terminal. Heating element supports from 5V to 12V.
• I2C address is set to 0x44 permanently. On this board layout this address can not be changed. Track between SHT30 address pin is connected to GND directly under sensor chip itself.

Specification:

• Diameter: 29 mm
• Humidity and temperature sensor: Sensirion SHT30
• SHT30 supply voltage: 3.3V
• I2C Address: 0x44
• I2C pull up resistors: 10k Ohm
• MOSFET: DMG3420U-7
• Recommended PTC Heating Element voltage: 5-12 V
• Max PTC Heating Element voltage: 20 V
• Max PTC Heating Element current: 5A
• Made in Poland :)

Links:

• Documentation