Automatic cooling fan: LM35 + LM358 + MOSFET
Open in the lab ▸Make my own copy
A fan that switches itself on when it gets warm. The LM35 gives 10 mV per °C (0.34 V at 34 °C). Half of an LM358 compares it with a set point from the SET knob (a 100 k + 10 k pot divider gives 0–1.1 V, so 0–110 °C; here it is set to 30 °C). Above the set point the op-amp output goes high, the IRLZ44N logic-level MOSFET turns on and the fan runs. The fan is a 5 V one, so an LM2596 buck module makes 5 V from the 12 V battery; a 1N4007 across the motor catches the kick when it switches off, and the blue LED shows when the fan is on. Try it: click the LM35 and change its temperature, or turn SET.
What is on the bench
27 parts, 39 wires.
| Resistor | 5 |
|---|---|
| LiFePO4 battery | 1 |
| Fuse | 1 |
| LM35 temperature sensor | 1 |
| Potentiometer | 1 |
| Op-amp | 1 |
| N-channel MOSFET | 1 |
| Step-down converter | 1 |
| DC motor | 1 |
| Rectifier diode | 1 |
| LED | 1 |
Put it on your page
The project runs live inside the frame: readers can press buttons, turn knobs and read the meters.
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Link
https://zencircuitlab.com/p/zclfanthermo
Published by its author under the lab's community terms: it may be opened, copied and changed by anyone. Simulation results are for learning; check a real build against the parts' datasheets.