Solar Powered Nocturnal Personal Fan




A small fan, driven by a hobby motor. Powered by 2x AA rechargeable batteries. The batteries are hooked up to a solar panel, which recharges them during the day.
The circuit is switched by a CdS cell (light switch) which means the fan switches on when it is dark enough, at night, hopefully.
Only after I'd built the (incredibly ugly - sorry, no photos available) prototype did I realise I could've bought a pesonal fan for $5 and hacked it instead.
Here's the schematic. Feel free to use it or improve upon it to your own satisfaction.

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Step 1: Parts, Clarification, That Is.

The transistor is an ordinary NPN 100mA 45V.
The CdS I hacked from a solar garden light.
The solar panel came from the same place.
It's output is (rough estimate) 4.5V, 60mA.
I used an old hobby motor with a range of 2-6 volts. No special reason, it was handy. And the propellor came from a model plane.
That leaves the diode, 1N4004, and the two resistors, 1k and 10k.

Step 2: Other Uses

This isn't really a step, more a note about other things I've done with this - putting a white LED driver circuit in place of the motor.
A variation of the idea of the solar garden light I got the parts from originally.

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    11 Discussions

    Esther Nakamya

    Question 1 year ago on Step 1

    what is the use of the 10k ohm resistor , 1k resistor, the LDR and the transistor


    10 years ago on Introduction

    What's the purpose of the 1K resistor? It will work just fine without it. Change the 10K fixed resistor to a potentiometer to be able to adjust the point at which the transistor turns on. Swap the positions of the 10K and photo-resistor to create a "light on" switch. Also, the diode doesn't have to be a 1N4004. Any 1N400x series diode will suffice.

    2 replies

    Reply 4 years ago on Introduction

    You need to be careful with the potentiometer: if the user sets the resistance to 0 , then there will be a short through the base-emitter junction, which will probably destroy the transistor. So you can adjust the turn-on point with a pot, but you should include a fixed resistor also, e.g., the 1K as shown.


    Reply 10 years ago on Introduction

    Or if you give it a thermistor, you can have a temperature controlled fan.


    8 years ago on Introduction

    Hi there,
    I have a question here what is the meaning of LDR.Thanks u.


    10 years ago on Introduction

    I don't really understand are these just the Blueprints for the fan..?


    11 years ago on Introduction

    I guess no one will do this thing on a pcb, but just in case, here's a pic generated from croc tech 3d I edited it a little to make it more clear...