Temperature, humidity and liquid level multi-purpose automatic controller circuit diagram

As shown in the figure is a multi-purpose automatic control circuit for temperature, humidity and liquid level. The circuit consists of a step-down rectifier filter power supply circuit, a temperature and humidity sensor, a variable frequency oscillator and a monostable control circuit. The sensor can be equipped with a thermistor, photoresistor, mercury conductive thermometer and other sensing devices, and can be connected across the charge and discharge circuit of the 555 or the trigger end to change the frequency of the oscillator or the trigger state of the 555.

When the preset temperature is higher than the ambient temperature, the two mercury columns in the sensor leave and become open circuit, so that IC1 is reset because pin ② is at high potential, and pin ③ outputs low level, so that relay J1 does not operate. Turn on the power of the electric heating appliance to heat up; when the preset temperature is lower than the ambient temperature, the two mercury columns of the thermometer collide and form a short circuit, causing IC1 to be set because the ② pin is at low potential. ③Pin outputs a high level, causing relay J1 to close, correspondingly disconnecting the power supply of the electric heating appliance and stopping heating. Work in this cycle to maintain a certain temperature. The mercury conductive thermometer controls the temperature between 0 and 300°C, and the WXG-11t-50°C model can be used. If a temperature sensor Rt (thermistor) is installed and the temperature is controlled to be limited to the upper limit and lower limit, frequent starting and closing can be avoided.

Humidity control is realized by IC2 (555) monostable circuit. The working principle is similar to that of temperature control. It should be noted that the lower end of the hygrometer should be tied with absorbent cotton or gauze, and 2/3 of it should be immersed in water. Liquid level control is also implemented by the IC2 monostable circuit, and the working principle is similar to the above. What needs to be noted in the circuit is that an electrode is placed above and below the insulating rod placed in the water, as shown in the figure. Through a certain circuit connection form, this circuit realizes a variety of control functions.