Fan Controller Circuit with Thermistor and R4 - TehnikService.net

[Pyro123]

http://tehnikservice.net/2008/02/23/fan-controller-by-ic-741/

Guys Can you please illustrate how to connect the components to this layout.. especially the thermistor and R4..thank you !

 

[AugustCrawl]

Your IC1 op amp thing is probably part of a package... look at your chip and most likely it is an 8-pin package.
Typically the pins count down on the left side and up on the right side if you have it the right way up.1 5
2 6
3 7
4 8

So look at the numbers on the pins.. and put the components in around them.
R4 runs from pin 2 to ground.
R3 should be connected at one point to where R4 is connected to the pin.

is R1 your thermistor?

 

[Pyro123]

thank you for replying R1 is the thermistor yeah but actually the 741 op amp is

18
27
36
45

everything is quite clear except for R4 and the thermistor..there's only 3 holes in the ground area in the layout 1 for the fan 2 for the capacitor and the 3rd should be for either the thermistor or R4 while both of them should be connected..should i dig another hole or something ?!

 

[AugustCrawl]

It is not clear exactly from what you've said. A good idea is probably to take a non-blurry, well lit photo of the circuit as it is at the moment. I should be able to see clearly on that and help you further :)

 

[alphysicist]

Sure, I would be happy to provide some guidance on how to connect the components to this fan controller circuit. Let's start with the thermistor and R4.

The thermistor is a temperature-sensitive resistor that is used to sense the temperature in the circuit. It works by changing its resistance in response to changes in temperature. In this fan controller circuit, the thermistor is used to measure the temperature of the air and adjust the speed of the fan accordingly.

To connect the thermistor to the circuit, you will need to first identify the two leads of the thermistor. One lead will be connected to the positive rail of the circuit, while the other will be connected to one end of R4. R4 is a potentiometer, which is a variable resistor that can be adjusted to change the resistance in the circuit. The other end of R4 will be connected to the negative rail of the circuit.

Next, you will need to connect a wire from the other end of R4 to pin 2 of the IC741. This pin is the inverting input of the operational amplifier, which is the main component of the circuit. The thermistor and R4 form a voltage divider circuit, which produces a varying voltage at pin 2 of the IC741 depending on the temperature.

The other two components in this circuit are the transistor and the fan. The transistor acts as a switch, turning the fan on or off depending on the voltage at pin 2 of the IC741. When the temperature rises, the voltage at pin 2 increases, causing the transistor to turn on and the fan to start spinning. When the temperature decreases, the voltage at pin 2 decreases, turning off the transistor and stopping the fan.

To connect the transistor to the circuit, you will need to connect its collector to the positive rail, its emitter to the negative rail, and its base to pin 3 of the IC741. Pin 3 is the output of the operational amplifier, and it will send a signal to the transistor to turn it on or off depending on the voltage at pin 2.

Finally, you will need to connect the fan to the collector of the transistor and the negative rail of the circuit. When the transistor is turned on, the fan will receive power and start spinning.

I hope this explanation helps you understand how to connect the components in this fan controller circuit. If you have any further questions, please let me know.