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nRF52840 TMP36
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nRF52840 TMP36

by czuvich on Sun Apr 28, 2019 6:45 pm

I'm trying to read the output of the TMP36, but for some reason the temperature isn't changing. Is it required to hook the TMP36 to the 3.3V output for VCC or can I use one of the pins (for instance pin 9) and set pinMode(9, OUTPUT) and digitalWrite(9, HIGH)?

Right now I have hooked into pin 9, and it reads 72F (which is about right +/- a few degrees), but it's not changing when I put my hand around it.

czuvich
 
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Re: nRF52840 TMP36

by franklin97355 on Sun Apr 28, 2019 8:25 pm

What code are you running and how do you have it connected? Have you tried it the other way?

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Re: nRF52840 TMP36

by czuvich on Mon Apr 29, 2019 1:03 pm

So here's what I've tried:

1) A different TMP36 sensor
2) Connected to both 3.3V and PIN
3) Measured the voltage at the pin and output directly from the TMP36 (powered via the nRF52840).

The result is always the same (the reading doesn't really change much even if I drop the sensor into cold water or put my hand around it). I'm also seeing somewhat erratic results. I did find this forum post https://community.particle.io/t/tmp36-reading-analog-values-of-around-370-395-solved/4704 which discusses adding a small capacitor.

I ended up abandoning using a TMP36 to measure the temperature, and instead I am using the chip/die temperature (I'm just trying to get an idea how hot it's getting inside of an enclosure). Thank you for the consideration!

czuvich
 
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Re: nRF52840 TMP36

by franklin97355 on Mon Apr 29, 2019 1:20 pm

Have you tested the TMP36 with a meter to see if the problem is with the chip or the code/connection?

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Re: nRF52840 TMP36

by czuvich on Mon Apr 29, 2019 3:30 pm

I hooked up a DMM to the TMP36 and it did indeed register a proper voltage, but I did not see it change (maybe very slowly). I did have it powered directly from the nRF52840 regulated output (not to a battery). I've never used the TMP36 sensors, so maybe it's my misunderstanding of how quickly these sensors respond to temperature changes.

czuvich
 
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Please be positive and constructive with your questions and comments.