Humidity controller circuit design using NAND gate CD4011-humidity sensitive circuit

　　This circuit can detect the ambient humidity and control the humidification and drying equipment to keep the ambient humidity within the required range.

　　Working principle of the circuit: After the 220V AC mains power is stepped down by T, rectified by VD1~VD4, filtered by C1 and C2, and stabilized by IC1, a DC voltage of 9V is obtained to power the circuit. VL3 is the power indicator light. An oscillation circuit is formed by IC1 and R1, R2 and C3, which generates a pulse signal with a frequency of about 2.5KHz. After the signal is divided by RP1, RS and rectified by VD5, it is added to the base of V3 through R3. When the humidity changes, it will cause the RS resistance to change. When the humidity decreases, the RS resistance increases, causing the base potential of V3 to rise and turn on, which in turn turns V1 and V2 on and V4 off. Relay KA1 pulls in, driving the humidification equipment to work, and the humidification indicator VL1 lights up at the same time; When the humidity increases, the RS resistance decreases, causing the base potential of V3 to drop and cut off, which in turn turns on V4 and cuts off V1. The relay KA2 is closed to drive the drying equipment to work, and the drying indicator VL2 lights up at the same time. This ensures that the ambient humidity is controlled at the set value, and the ambient humidity is set by RP1. At the same time, adjusting RP2 and RP3 can adjust the working sensitivity of V1, V2 and V3.

　　Selection of components: Integrated circuit IC1 uses the CD4011 2-input four-NAND gate integrated block. Other models include CC4011, MC14011, etc. Other NAND gate circuits with the same functions can also be used; IC2 is a three-terminal integrated voltage regulator 7809 , LM7809, CW7809 and other models can be selected; RS uses a universal humidity sensor, which requires that when the humidity is 30%, its resistance value is about 10MΩ; when the humidity is 50%, its resistance value is less than 200KΩ; when the humidity is 90%, its resistance value is The resistance is about 10KΩ. Transistors V1 and V4 use NPN type transistors 8050, or domestically produced transistors such as 9013 or 3DG12; V3 uses 9014 or 3DG6; V2 uses 9012 or 3CG21. VD1~VD4 use rectifier diode 1N4007; VD5 uses 2AP9 or 2AP10 germanium diode; VL1~VL3 uses ordinary light-emitting diodes. Resistors R1 ~ R6 use 1/4W metal film or carbon film resistors. RP1~RP3 use organic solid core potentiometers. C1 and C2 use aluminum electrolytic capacitors with a withstand voltage of 16V; C3 uses porcelain capacitors. KA1 and KA2 use micro relays with a coil voltage of 6V, and the contact capacity is determined according to the power of the humidifying and drying equipment.

　　After the circuit installation is completed, start the humidification equipment. When the humidity reaches the upper limit, adjust RP1 and RP3 to stop the humidification equipment; when the humidity drops to the lower limit, adjust RP2 to start the drying equipment. Repeatedly adjust the above potentiometer to ensure that the equipment works reliably and does not produce critical oscillation, that is, the debugging is completed.

　　Boil water on the kitchen gas stove. Once the water boils, if you don't turn off the flame in time, the boiling water will overflow and put out the flames. Gas leakage is very unsafe. This problem can be solved by using the water boiling alarm.

　　Working principle of the circuit: This circuit uses a thermistor as the temperature sensing element. When the water temperature increases, the resistance of the thermistor decreases and the potential of point A increases. When the potential of point A is higher than the IC-1 inverter conversion When the voltage is high, IC-1 will output a low level and IC-2 will output a high level. Make the audio oscillator composed of IC-3 and IC-4 work, and the piezoelectric ceramic sheet produces sound. When IC-2 outputs low level, the audio oscillator composed of IC-3 and IC-4 does not work, and the piezoelectric ceramic piece is silent. The IC uses a C066 two-input four-NAND gate with an operating voltage of 3V to 18V. In this circuit, the power supply is 3V to 6V; the resistance of the RT thermistor is about 1kΩ; the diameter of the piezoelectric ceramic piece is 27mm; the resistance is of ordinary 1/8 or 1/4W metal film resistors.

　　Production and debugging method: Find two scrap fluorescent lamp starter shells, use iron sheets as clamps, stick the tops of the two starters together, and tighten them with screws. One of the starters can be placed on the mouth of the kettle to obtain the temperature of the water. The two pins of the thermistor are welded to the cover of the other starter and installed into the shell. Note that the thermistor must be close to the inner shell wall to facilitate heat transfer. Solder the outer leads of the thermistor and the temperature sensor is ready. After all the components are welded and checked, you can turn on the power for debugging, put the temperature sensor on the kettle spout, and adjust the RP when the water boils so that the piezoelectric ceramic piece makes the right sound. Repeat debugging a few times before it can be officially used. If you want to change the sound frequency, you can change the capacity of C2. If you feel that the sound is not enough, you can connect an external triode to the output of IC-4 to amplify the sound effect.