Skip to main content

Temperature Controled Fan

This circuit controls very accurately a fan of any size. Just adjust the associated resistors for a different type like the R6 resistor of 100 ohm, 2 watt type and you're all set. The above circuit diagram is for a small 12 volt fan, the size and type determined by the user.

Temperature is sampled via the 1N4148 diodes and presented at pins 2 and 3 of the differential type 741 op-amp. R7 (10K) is used to create a voltage difference between the inverted and non-inverted input pins 2 and 3 of the 741. All signals presented at pin 2 will be inverted on the output pin 6. Obviously then, the input pins are very important. When pin 2 goes more positive than pin 3, the output pin 6 of the 741 goes high and forward biasing the base of transistor Q1, which switches on transistor Q2 and the Led and puts 12V on the output pins for the fan. R9 functions as a feedback for the 741. Only DC type fans can be used with this schematic diagram without further modifications.

The temperature sensor is made up of three easily available 1N4148 signal diodes mounted in parallel. Mount them in a thin aluminum, or plastic tube (depending on your application) and silicon the end of the tube to make this temperature sensor water-proof. As an additional note, I have seen this type of temperature sensor, with the diodes either in parallel or series and either 1 or more diodes, in all sorts of laboratory equipment like hot water baths and others. The water bath temperature setting ranged from room temperature to about 100° Celsius. Keep in mind that using the 1N4148 diode as a temperature sensor is very accurate when used within the specifications of the 1N4148.

Parts List:
R1 = 560 ohm                                    Q1 = 2N2907 (NTE159M) low noise
R2,R9 = 100K                                   Q2 = MJE521 (NTE184)
R3,R8 = 10K                                     IC1 = 741, op-amp
R4,R7 = 1K                                       Led1 = LED, red
R5 = 470 ohm                                    D1,D2,D3 = 1N4148, signal diode
R6 = 100 ohm, 2watt, wire-wound       D4 = 1N4004, general purpose diode 
P1 = 100K, trimmer pot
 C1 = 2.2uF, 25V, electrolytic
C2 =  47uF, 25V, electrolytic


Popular posts from this blog

Build a Low Noise And Drift Composite Amp Circuit Diagram

How to Build a Low Noise And Drift Composite Amp Circuit Diagram. This circuit offers the best of both worlds. It can be combined with a low input offset voltage and drift without degrading the overall system`s dynamic performance. 
 Low Noise And Drift Composite Amp Circuit Diagram

Compared to a standalone FET input operational amplifier, the composite amplifier circuit exhibits a 20-fold improvement in voltage offset and drift. In this circuit arrangement, A1 is a highspeed FET input op amp with a closed-loop gain of 100 (the source impedance was arbitrarily chosen to be 100 kfl). A2 is a Super Beta bipolar input op amp. It has good dc characteristics, biFET-level input bias current, and low noise. A2 monitors the voltage at the input of A1 and injects current to Al`s null pins. This forces A1 to have the input properties of a bipolar amplifier while maintaining its bandwidth and low-input-bias-current noise.

High Power Output Amplifier TDA7294

The famous SGS-THOMSON ST Microelectronics has introduced a Hi-Fi DMOS high-power amplifier circuit TDA7294, its sound great taste bile, which due to its internal circuit from input to output are field-effect devices, rounded sound Mild, delicate Rounuan.  However, with its assembly amplifier, only TDA7294 single-output power is only 70 W, BTL access law is 100 W from top to bottom, do not feel that power cushion. The author several tests, used to promote TDA7294-level, direct-drive one to four pairs of high-power transistor parallel, the output of strong currents, the power output of 400 W (mono), and the circuit is simple and no need to debug that can reliably work Basically, the IC has maintained a sound and performance.  Ruzuo The figure below shows, R6 for the feedback resistor, the author of the value in debugging 22 k Ω more appropriate, R6 also decided this circuit gain, the gain value will increase.  Quiescent current depends on the power of R7, R8, when its value…

Full Power Mobile Phone Jammer Circuit Diagram

Full Power Mobile Phone Jammer Circuit Diagram.To day if we are talking about expert Cell phone Jammers we are conversing about this schematic underneath. First off all you should be very very cautious how to use this apparatus. Its completely illegal and so the reason. I post this Circuit is only for educational and testing causes. This type of apparatus is being utilised by security for VIPS, particularly at their limousines to avoid blasting device initiating while the vehicle passes from the goal cell phone-bomb. Off course there are those who use it to make a antic or to make the persons crazy in the rectangle block you are. 
The power of the jammer is currently sufficient to do your thing, but certainly you can place a 30W linear power amp at the RF output and impede a much wider locality. So, Be pleasant individual with that and recall that there are people who may need desperately to obtain or make a call and one of them could be you! And if you can't oppose of functioning …