Electronics Q - sound concept?

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1

Looking for a quick way to turn on a 5v DC fan on based on a temperature value.

For this project I’d eventually add more sensors, Wi-Fi and a mainboard. But just for a quick PoC, want to do it a via passive components.

Could I use a temp sensor that has an analog output (like this: https://www.sparkfun.com/products/10988 ) feed into an NPN, with it being the on/off switch for the fan?

I understand there’d be downsides to this solution (for example, with no PID-like control, the fan might cycle on/off frequently).

In this design, could I use a 555 for speed control?

Are there other “better” solutions (with the understanding I want .NETMF it later on)?

2

Of course, depending on your needs… There are computer fans that have this already built-in. I’ve never tried it but I would bet that you could crack one open and tune a resistor to whatever temperature you desire.

3

Or get one of these :

Pretty cheap… And hack friendly I’m sure :slight_smile:

Edit: the better version.

4

Huh. I wonder if the probe is (or could be made to be) food-safe.

5

An analog input to a comparator will work but without some kind of hysteresis will tend to toggle on an off around the switching point.

The good old LM339 would work and I found in a quick search some hysteresis circuits for it.

6

Thanks for input