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This temperature indicator indicates the temperature of a heat sink in high power circuits .In this temperature indicator, diode voltage drop in ambient temperature is used as reference level. Temperature is measured by a transistor mounted on a radiator or near power transistor controlled.T1 temperature sensor and voltage to the base - emitter is compared, through potentiometer P1, with the common point of reference in its D1 and R1. Transistor remains blocked as long as temperature remains below a certain level, which is set to P1. Base-emitter voltage of transistor will decrease by about 2 mV for a temperature increase of about 1 ° C. When the emitter voltage of transistor voltage falls below the cursor P1, the transistor will go into conduction and D2 will light.The values of R1 and R2 are voltage dependence of Ub and relationships can be calculated: R1 = [(Ub - 0.6) / 5] k, R2 = [(Ub - 1.5) / 15] k. Temperature Indicator  Schematic

If your PC overheats, it could damage its expensive components. Here’s a circuit that warns you of your PC getting heated. Today’s computers contain most of the circuitry on just a few chips and reduced power consumption is a byproduct of this LSI and VSLI approach. Some PCs still have power supplies that are capable of supplying around 200W, but few PCs actually consume power to this extent. On the other hand, apart from some portable and small desktop computers that use the latest micro-power components, most PCs still consume significant amount of power and generate certain amount of heat.  The temperature inside the aver-age PC starts to rise well above the ambient temperature soon after it is switched on. Some of the larger integrated circuits become quite hot and if the temperature inside the PC rises too high, these devices may not be able to dissipate heat fast enough. This, in turn, could lead to failure of devices and eventually of the PC.  Various means to combat overheati...

This is a very simple electronic circuit project of light sensitive and differential temperature switch circuit.   In Fig. 1 see a precision light- sensitive switch that activates when the sensed quantities go above or below pre-set values. The LDR can be any cadmium – sulfide unit that has a resistance in the range 500R to 20k at the required trip level. The RV1 adjust LDR at normal light level. In Fig. 2 see a differential temperature switch circuit using ordinary silicon diodes as temperature – sensing elements and responding to differentials of a fraction of degree. RV2 can be used to apply an effective offset of several degrees to the two diodes. To adjust the circuit, apply the required differential temperature to the diodes and then adjust RV2 so that the relay just turns on. The circuit responds to the relative temperatures, rather than the absolute temperatures, of the two diodes.

Basic circuit of the LM35 are made to control the fan is either used on amplifier that requires automatic cooling. Its use on power amplifier circuit above and only requires DC fan. From basic sensors based on ic and amplifier op-amp is added again to the transistor Q1 to drive the fan. Part List : R1___220K R2___100K R3___3K3 R4___22K R5___1M R6___150R R7___2K2 R8___33R 4W C1___100pF D1___1N4148 IC1__7915 IC2__TL072 IC3__LM35 F1___DC Fan 12V

This is a simple speed control temperature DC fan circuit diagram . This simple circuit based on two transistors that can be used to control the speed of a 12 V DC fan depending on the temperature.A thermistor (R1) is used to sense the temperature.  When the temperature increases the base current of Q1 (BC 547) increases which in turn decreases the collector voltage of the same transistor. Since the collector of Q1 is coupled to the base of Q2 (BD 140), the decrease in collector voltage of Q1 forward biases the Q2 more and so do the speed of the motor. Also, the brightness of the LED will be proportional to the speed of the motor.  Simple Speed Control Temperature DC Fan Circuit Diagram Notes. The R1 can be a 15K @ 20°C ,N.T.C  thermistor. The M1 can be a 12V,700mA fan motor. The capacitor C1 must be rated 25V. The circuit can be powered from a 12V PP3 battery or 12V DC power supply. Assemble the circuit on a good quality PCB or common board. Sourced By: Streampowers

Description. Here is a simple circuit based on two transistors that can be used to control the speed of a 12 V DC fan depending on the temperature.A thermistor (R1) is used to sense the temperature. When the temperature increases the base current of Q1 (BC 547) increases which in turn decreases the collector voltage of the same transistor. Since the collector of Q1 is coupled to the base of Q2 (BD 140), the decrease in collector voltage of Q1 forward biases the Q2 more and so do the speed of the motor. Also, the brightness of the LED will be proportional to the speed of the motor. Circuit diagram with Parts list. Notes. The R1 can be a 15K @ 20°C ,N.T.C  thermistor. The M1 can be a 12V,700mA fan motor. The capacitor C1 must be rated 25V. The circuit can be powered from a 12V PP3 battery or 12V DC power supply. Assemble the circuit on a good quality PCB or common board.

This radiator temperature indicator can be designed using electronic circuit diagram bellow .Temperature indicator consists of two special zener diode, D1 and D2, connected in series to ensure accuracy of 5.96 V Zener voltage at 25 ° C. As long as the radiator temperature not exceeding 50 ° C, thermal indicator will flash a green LED, one orange will be provided for temperatures of 50 ... 75 ° C and a red LED, for temperatures above 75 ° C. Zener voltage will increase by 20 mV for each temperature increase of a degree Celsius temperature. Radiator temperature corresponding voltage level is compared with two reference voltages, IC1 and IC2 using. When the temperature reaches 50 ° C, IC2's output goes to logic state "1" so that T3 leads and following ignition with diode D4. At 75 ° C, IC1's output is in logic state "1" and, therefore, T2 and T3 will, so that D3 and D4 lights are off. 

LED based projects require a lot of skill and hence only experienced circuit designers try out these circuits. But there are also a few circuits in this genre that can be done by amateur electronic hobbyists. The temperature candle is one such circuit. Read on to know more about this. The hardware components that are required to build this circuit are listed below: Microcontroller Temperature Sensor RGB LED PCB The circuit design is pretty simple. The LED is made to flicker by the microcontroller and the color is based on the ambient temperature at that point. The temperature of the room can be known by observing the color of the LED. The temperature value is obtained in degree Celsius. This value is received as a result of pressing the reset button on the PCB. This value can also be obtained by providing power to the device. Once the device is powered up, the change in temperature is indicated. The blue LED is triggered for a temperature increase of 10 degrees. The red LED is trig...

T his t sink in high power circuits. In this temperature indicator, diode voltage drop in ambient temperature is used as reference level. Temperature is measured by a transistor mounted on a radiator or near power transistor controlled.T1 temperature sensor and voltage to the base - emitter is compared, through potentiometer P1, with the common point of reference in its D1 and R1. Temperature Indicator circuit diagram Transistor remains blocked as long as temperature remains below a certain level, which is set to P1. Base-emitter voltage of transistor will decrease by about 2mV for a temperature increase of about 1 ° C. When the emitter voltage of transistor voltage falls below the cursor P1, the transistor will go into conduction and D2 will light.The values of R1 and R2 are voltage dependence of Ub and relationships can be calculated: R1 = [(Ub - 0.6) / 5] k, R2 = [(Ub - 1.5) / 15] k