Developing a temperature-controlled DC fan using an LM741 Op amp and an NTC thermistor to regulate the bedroom temperature sounds like a promising project to improve sleep quality for people with insomnia.
The primary objective of this project is to develop a cost-effective and adaptable temperature control system using a temperature-sensitive sensor (NTC thermistor) and an operational amplifier (LM741). By accurately monitoring the ambient temperature, this system will automatically activate or deactivate a DC fan to achieve and maintain the desired temperature setpoint. The key goals of this project include:
- NTC Thermistor:
- An NTC (Negative Temperature Coefficient) thermistor is a temperature-sensitive resistor whose resistance decreases as the temperature increases. You'll need this to measure the bedroom temperature
- LM741 Op-Amp:
- The LM741 is a commonly used operational amplifier that can be configured to amplify the voltage difference between the NTC thermistor and a reference voltage to control the fan.
- DC Fan:
- Choose a DC fan suitable for the size of the room and the desired airflow. Ensure that it can be easily powered and controlled.
- Power Supply:
- You'll need a suitable power supply for the fan and the op-amp circuit. Make sure it can provide the required voltage and current.
- Resistors and Capacitors:
- You may need resistors and capacitors to set up the op-amp circuit and to filter any noise.
- 1N4007 Diode:
- The 1N4007 diode can be used for flyback protection when controlling inductive loads like DC fans. When the fan is turned off, the collapsing magnetic field can induce a voltage spike that could potentially damage the circuit. The diode, when connected in parallel with the fan, allows this voltage to safely dissipate.
- BD140 Transistor:
- The BD140 is a PNP transistor that can be used as a switch to control the power supply to the DC fan. It amplifies the current from the LM741 op-amp to drive the fan effectively.
Circuit Schematic At LTSpice
The Circuit Design is simple, Negative temperature coefficient (NTC) Thermistor decreases its resistance when the temperature increases while Positive temperature coefficient (PTC) increases its resistance when the temperature increases. Here a 4.7K NTC Thermistor is used, 741 is used as a voltage comparator to switch on the DC fan. Its INV input (pin2) gets an adjustable voltage through VR while its non-INV (pin3) input gets voltage through a potential divider comprising R1 and the Thermistor. Thus, the voltage at pin3 depends on the conductivity of the Thermistor.
Circuit Working Video
