WATER HEATING CONTROL CIRCUIT

Abstract

The useful solution refers to a heating control circuit for a water heater using a DC power supply of approximately 24VDC and an NTC thermistor sensor with a nominal value of approximately 10 kΩ at 25°C. The control circuit includes an input power supply block, a voltage regulator block, a noise filter and power protection block, a temperature signal processing block, a microcontroller block with an analog-to-digital converter (ADC), and a relay control block consisting of an intermediate control transistor and a protection diode connected in parallel with the relay coil. The microcontroller block is also configured to calculate the rate of temperature change, detect temperature sensor errors, detect inefficient heating conditions, detect the risk of dry heating, and switch the system to a safe fault state when abnormal situations occur.