cheap and simple way to measure temperature

[ardhuru]

When I made my POV propeller clock I was also tempted to include temperature display, besides the time and the calendar. What gave me second thoughts was the fact that the PCB would be spinning all the time, and therefore the temperature being displayed was unlikely to be exactly the ambient.

Are you sure your POV stick, while it is being waved, would also not influence the sensor's readings?

Just a thought...

Anand

[mackrackit]

Hand motored... That sounds interesting. They could even put them on the spokes of their bikes.

The LM34 may not be the best option then.

[El_AMPo]

When I made my POV propeller clock I was also tempted to include temperature display, besides the time and the calendar. What gave me second thoughts was the fact that the PCB would be spinning all the time, and therefore the temperature being displayed was unlikely to be exactly the ambient.

Are you sure your POV stick, while it is being waved, would also not influence the sensor's readings?

Just a thought...

Anand

Check how old fashion wet bulb hygrometers work,
http://www.agri-shop.co.uk/whirling-hygrometer-37-p.asp
Spinning all around but still the best readings, so no problem with the winding, probably a bad idea because of line noise if you weren't using batteries, but is not the case.

If you want a really CHEAP thermometer with decent accuracy use a diode as a sensor.
Here is the schematic:


Still working for me at a 0.5ºC resolution, but needs a two point slope calibration, some chip math and a pic with ADC.

Maybe the 10bit ADC will give you a resolution of 2-3ºC, maybe less with oversampling with just the 4k7 resistor and the diode directly to the adc.
Anyone for the test of oversampling?
http://www.darreltaylor.com/DT_Analog/

[fixitjs]

Be careful not to confuse ambient temperature with wind chill. objects will not cool to a lower temperature then the ambient temp, but will cool at a rate of the wind chill. thus, swinging the isplay stick will give you an accurate temp reading as any temperature increase caused by holding it will be released by the air flow accrossed the stick but not lower then the ambient temperature. hope this is helpful.

[mtripoli]

Have a look at the LM94022. Price is $1.27 from Digikey you can get the data sheet there as well (I had a link but Digikey uses scripts and the link comes out bad). It has a couple of options for gain set through pins. The biggest downside to this part is the package; not user friendly for hand soldering.

IIRC the LM34 is a little weird that it requires a negative bias to give voltages below 0 or something, and it only operates down to 5V.

Good luck.