Heat Activated Cooling Fan Controller Circuit Using LM393-LM358 & LM35 Temperature Sensor

Heat activated cooling fan controller ( Thermal Activated Cooling Fan Driver Circuit) is a simple project which operates a Brush-Less fan when the temperature in a particular area goes above a set point, when temperature return normal, fan automatically turns off. The project is built using LM358 Op-amp ( Use LM393 instead for good performance) ,  and LM35 temperature Sensor. Project required 12V DC supply and can drive 12V Fan. This project is useful in application like Heat sink temperature controller, PC, heat sensitive equipment, Power supply, Audio Amplifiers, Battery chargers, Oven.

The SMD SO8 LM35 used as temperature sensor, LM358 act as comparator provides high output when temperature rise above set point, high output drive the Fan trough driver transistor. The LM35 series are precision integrated-circuit temperature devices with an output voltage linearly-proportional to the Centigrade temperature. The LM35 device has an advantage over linear temperature sensors calibrated in Kelvin, as the user is not required to subtract a large constant voltage from the output to obtain convenient Centigrade scaling. The LM35 device does not require any external calibration or trimming to provide typical accuracies of ±¼°C at room temperature. Temperature sensing range 2 to 150 centigrade. LM35 provides output of 10mV/Centigrade.

NOTE :  It is  advisable to use LM393 Comparator instead of LM358 as it will provide better results.

  • Supply 12V DC 1Amps
  • Fan 12V DC , 500mA
  • Range : 2 °C to 150 °C
  • Open Collector Output
  • It can drive PC fan
  • Onboard preset to set the Fan trigger level
  • Onboard Power LED
  • Onboard Output LED
  • Output Driver Transistor
  • Header Connector for Supply and Fan
  • PCB dimensions 59.85 mm x 12.70 mm

Watch Video of the project available here

 

 

 

 

 

 

LM35 Temperature Sensor

The LM35 series are precision integrated-circuit temperature devices with an output voltage linearly-proportional to the Centigrade temperature. The LM35 device has an advantage over linear temperature sensors calibrated in Kelvin, as the user is not required to subtract a large constant voltage from the output to obtain convenient Centigrade scaling. The LM35 device does not require any external calibration or trimming to provide typical accuracies of ±¼°C at room temperature and ±¾°C over a full −55°C to 150°C temperature range. Lower cost is assured by trimming and calibration at the wafer level. The low-output impedance, linear output, and precise inherent calibration of the LM35 device makes interfacing to readout or control circuitry especially easy. The device is used with single power supplies, or with plus and minus supplies. As the LM35 device draws only 60 µA from the supply, it has very low self-heating of less than 0.1°C in still air. The LM35 device is rated to operate over a −55°C to 150°C temperature range, while the LM35C device is rated for a −40°C to 110°C range (−10° with improved accuracy). The LM35-series devices are available packaged in hermetic TO transistor packages, while the LM35C, LM35CA, and LM35D devices are available in the plastic TO-92 transistor package. The LM35D device is available in an 8-lead surface-mount small-outline package and a plastic TO-220 package.

 

LM358 Op-Amp

These devices consist of two independent, high-gain frequency-compensated operational amplifiers designed to operate from a single supply or split supply over a wide range of voltages.

LM393 Comparator

These devices consist of two independent voltage comparators that are designed to operate from a single power supply over a wide range of voltages. Operation from dual supplies also is possible as long as the difference between the two supplies is 2 V to 36 V, and VCC is at least 1.5 V more positive than the input common-mode voltage. Current drain is independent of the supply voltage. The outputs can be connected to other open-collector outputs to achieve wired-AND relationships.

LM293A devices are characterized for operation from −25°C to +85°C. The LM393 and LM393A devices are characterized for operation from 0°C to 70°C. The LM2903, LM2903V,

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