WSN: Temperature Sensor

The temperature sensor is based on the TMP36 Low Voltage Temperature Sensors.

My first attempt at creating a wireless temperature sensor was using a TMP36 device from Analog.  The TMP36 looks like a transistor because it is in a TO-92 package.

I soldered together an XBee Adapter board from Adafruit then I soldered the TMP36 directly to the adapter board.  Using the layout above. I soldered the voltage input pin to the closest VCC trace, the ground to ground (obviouisly) and the Analog Voltage output pin to the AD0 pin.

TMP36 on the XBee adapter

TMP36 on the XBee adapter

This seems to work fairly well if you only have one input.  If you plan to use multiple sensors on the XBee ADC inputs, you’ll need to set up a rail to rail op amp buffer.  But that’s for another post.








Here’s a live sample of a TMP36 data stream from my back porch as derived from a chart on

Large spikes are a known problem with the data collection downstream of the TMP36 and the XBee module.  To be fixed soon, I hope.


Next Post: Gas Sensor
Next Group: Radio:XBee

10 thoughts on “WSN: Temperature Sensor

  1. what is the issue with the xbee and multiple adc inputs? I ask because I am getting unusual readings from the tmp36, things seem to float around +- 3 Degrees C every few seconds.

  2. In general the readings of the TMP36 have been fairly solid. The issue I was seeing was between the various pins; like 19, 20. I would see some drift in one when the values in the other would go up or down. I did some research; asked around on some forums and came to the conclusion based on the advice I got that I should include an op-amp between the analog output and the xbee analog input. I used a TI TLC 2274 IN quad op amp.

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  5. Have you posted how you weatherproofed your porch temperature station? I’ve made a similar temperature circuit but I couldn’t figure out how to weatherproof the TMP36 while still having it touch the ambient air (and not the inside of an enclosure).

    • I have not written about how I enclosed my TMP36 outdoors.

      A few years back the sister of a friend was decommissioning a research project in the California Sierra mountains. She had about 300 chickadee bird houses that were retrieved from the woods where she was studying habits of birds.

      I became the recipient of about 20 of those birdhouses so I set one up as a temperature gauge station.

      I’ve got a small plastic box (the kind you get when you buy lunch meats) as the internal housing. It holds an xbee radio breakout board from Adafruit. I soldered the TMP36 (3.3V, Gnd, pin 19) directly to the breakout board. Included is a 1200 mAh LiIon battery to power it and I put a 2W solar panel on the roof of the birdhouse to charge the battery.

      The birdhouse remains in the shade and it has been working like that for about 3 years now. A few months ago, I looked at the setup and the LiIon battery is a little swollen, but so far it is still working.

      For the first year or so, I had a commercial wireless sensor (a cheapie marketed by in the birdhouse with my homemade version and they tracked well together.

      So far so good.

      BTW, I have set up a few other birdhouses with wifi cameras peeking out of the little chickadee bird doors.

  6. Hi, i have a questions of this sensor, because i used this sensor for measure corporal temperature of a cow, i have a caddle, and i want to measure the temperature of each cow, the temperature have a issues of reading, i read the solution, but i have a opamp 741, this operational it is reliable for the measurement?

  7. I enjoyed your post. I am new to this hardware and dont have any background in circuit design. Got a very silly question for you. After soldering the TMP sensor on XBee do we have to add/solder anything else other then powering it on and receiving the data on base station?

    • Nothing else. You need to configure the xbees on the sensor and on the base station, but as far as the physical connections, that’s it. You’ll need to configure the sensor radio to read the sensor values on an analog input and then set up the base station xbee to pull that in.

      Have fun,

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