XBee remote temperature sensor

There were some questions over time on how the remote sensors on my XBee network are actually wired up and I discovered that I only showed the sensor as is and never explained the wiring. So now this is done with this post and a breadboard picture made with Fritzing:

Remote temperature sensor with XBee

Hardware
The actual remote sensor has the components just soldered to a stripboard (which works for years now outdoors without any problems). For voltage regulation I use the low quiescent current LDO from Microchip MCP1700-3302E (3.3V, TO-92 style, ~1µA quiescent current consumption). There are 1µF ceramic capacitors both on the raw voltage input and the regulated output (just followed the typical application advice on the datasheet).
The temperature sensor TMP36 is wired to Ground, the Vout is connected to pin 20 of the XBee (AD0/ DIO0/ commissioning button) and Vin is wired to pin 13 (ON/ SLEEP).

The trick with consuming power for the temperature sensor only when the XBee is awake is to wire it to pin 13 (ON/ SLEEP) which is only powered when the XBee is awake.The sensor takes about 50µA when powered and is fast enough to get a temperature measurement while the XBee is not sleeping and takes samples from the AD0-Input (pin 20 XBee).

Temperature sensor on stripboard

My sensors are all powered with three AA cells for now and there is enough room from about 4.8 volts when full and fresh to 3.3 volts when it hits the regulated voltage. The sensor even works below that because I think the supply just gets pulled through the voltage regulator when at or below the regulated voltage.
The circuit draws only about 2.3µA when the XBee sleeps and about 40mA when awake but only for a very short amout of time. So the batteries last about are year or longer.


Software
 There is not much software involved beside configuring the logic on the XBee. Those are my settings:

SENDER: (REMOTE SENSOR )
END DEVICE
ATID 2001 (PAN ID)
ATDH 0
ATDL 0
ATD0 2     pin 0 in analog mode with TMP36
ATIR 3E8  sample rate 1000 millisecs (hex 3E8)
ATSM 4     sleep mode cyclic sleep mode
ATSN B     number of sleep periods (hex B = 12 decimal)
ATSP 7D0  sleep period (hex 7D0 = 2000 ms * 10 = 20 seconds)
ATST 7D0  time before sleep 2 seconds (hex 7D0 = 2000 ms)

Output on a custom made display-box for the kitchen with bus schedule

So the sensor is configured to sleep for four minutes (roughly, the oscillator in the XBee circuit seems to be either imprecise or temperature sensitive) then waking up for two seconds, powering the temperature sensor, sampling two times and then go to sleep again. That's all it does. Voila!

There is still room to improve the project. For example one could add an energy harvesting module to the circuit so that no batteries are used to power the device. Another nice feature would be to take a measurement of the actual battery voltage, which could be done with a simple high resistance voltage divider on one of the analog inputs. It might also be clever not to wire the temperature sensor to pin 20 which is also the comissioning button just in case your XBee is reluctant to wake up.