[solved] DHT22 sensor used for FAN and the voltage is low on Fan

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1

Hi

I just posted a question on Arduino Forum and I have been told to post here for Electronics based query.
My post thread was here: DHT22 Arduino Programing - Programming Questions - Arduino Forum

Im rewriting the question and attaching the file.

I am using the source code from this website as a reference

Attached file is my wiring diagram.

When I am uploading the code, fan voltage is too low. Its only showing approx 1.9V which I am expecting same as battery voltage. Can someone help me where I am doing wrong. In the attached file, it shows where my voltage is low.

Any help would be highly appreciated.

Regards

Screen Shot 2017-05-03 at 3.09.48.png
Screen Shot 2017-05-03 at 3.09.48.png615×524 28.5 KB

2

The BC547 is rated for 100mA absolute max. Only good for a walnut-sized fan.
If your fan draws more than 50mA (and less than 500mA), use something like a BC337 or 2N2222.
Or a logic level mosfet.

A 1k base resistor assumes a collector (fan) current of <75mA.
Base current (for switching) should be between 1/10 and 1/20 of collector current for a small transisor.
If your fan draws e.g. 100-300mA, then a 220ohm base resistor is needed.
Leo..

3

Thanks @Wawa for the response. I will test what you suggested and keep updated. Thanks once again.

4

Hi @Wawa yeah you were right. It was transistor issue. I am just wondering that if I use 12V power supply instead of 3.9V then is that 2N2222 transistor is right one?

5

armbot:
I am just wondering that if I use 12V power supply instead of 3.9V then is that 2N2222 transistor is right one?

The answer depends on the stall current of your fan at that voltage.

With 12volt, it's less of a problem to loose one volt across the transistor.
I also mentioned using a logic level mosfet.
Leo..