Auto Electrics Thermostat for the auto fan
Thermostat from the fan can be adapted to the car. Such a system will be reliable, simple, it is available, as proven more than once. The device consists of three components – a thermistor designed for 10 kOhm, power transistor and adjustable resistor. Auto electrics. The thermostat for the car fan We need a high power transistor, which will play the role of the power component of the regulator and when you connect a powerful fan, it will carry large currents. The role of temperature sensor is given to thermistor. You will also need a multi-turn variable resistor of 10 kOhm, it will allow you to adjust the fixture more accurately.
To adjust the temperature we need, we will use a variable resistor. Thermistor, in fact, is a variable resistor, its resistance depends on the temperature, that is, the higher the temperature – the lower will be the resistance of the thermistor. Therefore, when the temperature increases, the speed of the cooler will increase. The thermistor in our case is a kind of thermal sensor, it should be mounted on the engine block or on the car radiator. The described system is well suited for the Soviet model cars, because they have a fan does not depend on the temperature of the liquid coolant. At the desire of the motorist can be replaced OEM transistor, a transistor more powerful, for example (IRFZ40, IRFZ46, IRFZ48, IRF3205, IRZF44, IRL3705). By the way, the power dissipation of the IRF3205 type transistor is quite high – two hundred watts.
The transistor must be mounted on a heat sink. When not large loads up to 50 watts of heat dissipation is not needed, the transistor must simply be fixed to the car body with insulating plates and obligatory washer. Next, by slowly turning the AC resistor, you need to set the desired temperature of operation of the system.
There are two types of thermistors, some have a positive temperature coefficient, others negative. From which follows a decrease in resistance if the temperature goes down and vice versa an increase in resistance if the temperature goes up. In our case the thermistor has a positive temperature coefficient. Read also: How to put a digital voltmeter in a dashboard When the thermistor heats up and reaches a certain temperature, the current supply to the gate of the power switch will stop, because of a sharp increase in resistance. Because of this, the field switch will close, the heating will stop, and the thermistor resistance will decrease (in our experiment, 220-230 Ohm, the temperature in the room is 19C). Resumption of current supply to the gate of the switch will cause it to open, and the fan will be energized again.
Installation of car relay instead of the load, will give the opportunity to connect the car cooling fan. If you take the AC resistor to a convenient place in the car cabin, we will be able to adjust the threshold for turning on and off the fan when the car moves. Using such a simple circuit makes it possible to design a sensitive temperature sensor, it can be found a worthy application in everyday life. Using very accurate (multi-turn) variable resistors, it is likely to turn on or off all sorts of devices, even on the temperature of the human body.
By connecting an electromagnetic relay with a certain current and voltage instead of a fan, we will be able to control powerful mains loads. As an example we can switch the heater off and on automatically when the room temperature changes. With bipolar transistors you can create a similar device if the therma sensors are replaced by germanium diodes.
Thermostat for the car fan, auto electrics
Thermostat for the fan, with confidence can be used for the car, auto electrics comes to the rescue. Such a system has repeatedly proven its availability, simplicity and reliability. The basis of the device, are only three components – trimmer resistor, power transistor and a thermistor of 10 kΩ. Thermostat – do it yourself!
You need a powerful transistor, because it will be the power part of the regulator and when you connect the fans of high power, it is through it flows a lot of current. A thermistor will be used as a temperature sensor. For more accurate adjustment of the device, the trim resistor of 10 kΩ is better to take a multi-turn resistor.
The desired temperature setting, as well as temperature sensitivity, can be adjusted by turning the variable resistor. Thermistor, in fact, is a variable resistor, its resistance depends directly on the temperature, the higher it is – the lower the resistance of the thermistor. The cooler, therefore, will increase rotation, precisely at higher temperatures.
The thermistor is a temperature sensor and is mounted either on the radiator or on the engine block.
Such a system, literally created, for old, domestic car brands, in which the fan runs, no matter what the temperature of the water in the engine. If you want, you can replace the field-effect transistor with a more powerful one, for example IRF3205, IRZF44, IRL3705, IRFZ40, IRFZ48, IRFZ46. By the way, the IRF3205 is quite strong, its power dissipation is 200 watts. Regardless of your choice, the transistor must be mounted on a heat sink (but for low-power loads, up to 50, the heat sink is not needed), it is simply attached to the car body, through the insulating plates and necessarily, washers.
Next, it is necessary to achieve the desired degree of temperature response of the system. This can be achieved by slowly turning the variable resistor.
It is known that thermistors are divided into two types, with a negative and positive temperature coefficient. And, as a consequence, with decreasing temperature, the resistance decreases, and with increasing, respectively, increases. In the considered experiment, a thermistor with a positive temperature coefficient was used.
When the thermistor heats up and reaches a certain temperature, its resistance increases sharply and the gate of the power switch stops supplying current. Because of this, the field switch closes and when the heating stops, the thermistor resistance decreases (in this experiment, 220 to 230 ohms at a room temperature of 19 degrees). The gate of the switch resumes supplying current so that it opens and supplies voltage to the fan.
If you put instead of load (a small fan) car relay, you can easily connect the car fan cooling switch, that is Karlsson))), and if you also put a variable resistor output to the instrument panel or just in the cabin of the car, it will be possible to adjust the threshold of the fan right on the move.
Using this simple circuit, you can build a fairly sensitive temperature sensor, which can be successfully used in everyday life. And if you use more accurate variable resistors (multi-turn resistors), it is quite realistic to achieve, triggering and tripping of various devices on the temperature of the human body.
To control powerful network loads, it becomes possible by connecting electromagnetic relay to the required voltage and current instead of the fan. Automatic switching on and off of the heater when the temperature in the room is higher or lower than normal can serve as an example. Also, a similar device can be built using bipolar transistors, using germanium diodes instead of temperature sensors.
And I also want to note one more point, if you have had an accident or you just decided to fix the body of your car, then there is an excellent center which is engaged in the body repair of the car. Trust the professionals and your body will be as good as new again.
