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Question regarding Tmp36 Sensor
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Question regarding Tmp36 Sensor

by desnotes on Sun Jul 04, 2010 11:53 am

I am trying to implement the TMP 36 temperature sensor and getting readings about 10 degrees C higher than they should be. I am running the sensor on 3.3 volts from an Arduino Duemilanove and am getting the "special indicator on pin 14 to measure the bandgap. Here are some typical readings:

RefReading (BANDGAP): 189
Supply Voltage: 5.69 (calculated from (1.05 * 1024) / refReading
TmpReading: 152 )analog reading from PIN 1)
TempVoltage: .84 volts (calculated from: (TmpReading * supplyVoltage) / 1024
TempC: 34.00 (calculated from: (TempVoltage - .5) * 100

The temperature in the room is a pretty steady 25 degrees C and is confirmed by a another sensor and a thermometer with humidity. Does anything stand out? I don't understand why the supply voltage reads so high when I am using the 3.3 volt pin. The Arduino is being powered by the USB line and thought that might be it.

Could it just be a bad sensor? Unfortunately I don't have an additional Tmp36 except for some SMD versions which I haven't soldered to a breakout board.

Any suggestions?

TIA,

desNotes
Tampa

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Re: Question regarding Tmp36 Sensor

by adafruit on Sun Jul 04, 2010 12:49 pm

dont use the bandgap, its inconsistant between arduinos, we have deleted that tutorial

refresh the page and use the new tutorial using the 3v ref

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Re: Question regarding Tmp36 Sensor

by desnotes on Sun Jul 04, 2010 1:33 pm

Thanks for the quick response. I will try it as soon as I get back home.


Thanks again,

desNotes

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Re: Question regarding Tmp36 Sensor

by desnotes on Mon Jul 05, 2010 11:12 am

I tried it last night and still could not get the numbers in the ballpark when using the 3.3 volts pin. I switched over to 5 volt pin and assigned "aref_voltage" to 5 volts and it worked successfully. Not sure what I did to make the 3.3 volt pin not work but will step through process again later and see what I missed.

Thank you for the support,

desNotes

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Please be positive and constructive with your questions and comments.