Rongge

The circuit consists of power supply and control sections. The power supply section is built around transformer X1, bridge rectifier BR1 and filter capacitor C1. The 50Hz, 230V AC mains is stepped down by transformer X1 to deliver a secondary output of 9V, 300 mA. The transformer output is rectified by the bridge rectifier and filtered by capacitor C1. Fan and Air-Conditioner Control Switch circuit Diagram When the mains is switched on for the first time, pin 3 of IC CD4017 (IC1) goes high and relay RL1 energises to switch on the fan. When mains is briefly switched off using S1 and then switched on, the power to IC1 is maintained by the charge on capacitor C1. At the same time, there is a trigger pulse on the clock input (pin 14) of IC1, which advances the decade counter and relay RL2 energises to switch-on the air-conditioner. Both the air-conditioner and the fan will be turned off if the switch is in the ‘off’ position. Assemble the circuit on a general-purpose PCB and enclose in a s...

Description This circuit is self explanatory and it is fairly simple, the temperature sensor used in this circuits are not thermistors but they are nothing but the signal diodes, the variation of the resistance according to increase or decrease in temperature sets the operational amplifier which drives the transistor Q1 which inturn gives the base voltage to transistor Q2 and their by the fan is switched on and off.  Circuit Diagram Source -http://www.electronguide.com/circuits_pages/TEMPRATURECONTROLLEDFAN.html

This is the simple Fan Speed ​​Control for Temperature Circuit Diagram. With this simple circuit that you will be able to control the speed of a DC fan according to the temperature measured by a temperature sensor. It is an ideal accessory for your projects that require cooling that are not constant.  This simple design allows precise speed control of motors, fans, and blowers, proportional to the temperature. An NTC thermistor (R1) is used as temperature sensor. A circuit optional was added to remotely monitor the operation of the fan and to allow some kind of indication of the approximate speed by increasing the brightness of an LED.  Fan Speed ​​Control for Temperature Circuit Diagram The R5 must be configured to allow the engine just starting to run at the desired temperature. Any 6K8 between the NTC thermistor 22K can operate provided that the R2 value is one tenth of the thermistor. R6, R7 and D1 are optional: R7 obligation is adjusted until the LED glow dimly when the e...

Circuit which is also equipped with temperature sensors would protect the high temperature. However, in the above circuit which necessiatated the input of the amplifier / audio signal. The way it works is , if the amplifier circuit to work and ouput signal to be connected to this circuit , Fan 12V will work well. If the received audio signal this circuit does not exist , then the fan 12V die. And automatic circuit amplifier also not work and does not require refrigeration. Part List : R1_________________220K R2,R9,R10,12,13_____100K R3_________________2K4 R4_________________22K R5_________________1M R6_________________150R R7_________________2K2 R8_________________33R 4W R11________________10K C1_________________100pF C2_________________47uF 25V C3_________________100uF 25V D1,D2______________1N4148 Q1_________________MJE350 Q2_________________MPSA42 IC1________________7915 IC2________________LM35 F1_________________Fan 12 Volt

This circuit is ideal to control the cooling fan of heat generated electronic gadgets like power amplifiers. The circuit switches on a fan if it senses a temperature above the set level. The fan automatically turns off when the temperature returns to normal. The circuit uses an NTC (Negative Temperature Coefficient) Thermister to sense heat. NTC Thermister reduces its resistance when the temperature in its vicinity increases.IC1 is used as a voltage comparator with two potential dividers in its inputs. Resistor R1 and VR1 forms one potential divider connected to the non inverting input of IC1 and another potential divider comprising R2 and the 4.7K Thermister supplying a variable voltage to the inverting input of IC1. VR1 is adjusted so as to give slightly lesser voltage at the non inverting input than the inverting input at room temperature. DC Fan Controller Circuit In this state, output of IC1 will be low and the Fan remains off. When the temperature near the Thermister increases, i...