Hi Everyone,
For my senior C.S. capstone project myself and three other guys are building wireless temperature and humidity sensors for a local museum. The museum's main constraints for the sensors are that they are inexpensive and last as long as possible on batteries. After examining many MCU's and transmission protocols (ZigBee, Bluethooth LE, ...) we settled on RFM69W Moteinos. They are inexpensive, have acceptable range, and can be run so that they use barely any power.
In our setup each Moteino is wired to a DHT22 temp/humidity sensor and powered by 3AA batteries (Fritzing only had a 2AA battery object;)). The DHT22 is powered from a pin so that it can be turned off and the Moteino is asleep and won't drawing any current. The devices will spend the vast majority of their life asleep.
Each Moteino transmits its data to a gateway Moteino connected to a Raspberry Pi. The Pi then POSTs the readings to an API on our website. The website has some graphs displaying recent readings and the status of the sensors (battery voltage and time since last transmit). Likewise, the museum staff can donwnload a CSV of all readings for a given date range.
Today we finished wiring up all of the sensors and are going to start a full scale test.
We plan on deploying the sensors to the museum in the next couple weeks so we can give them a run and troubleshoot before we graduate.
The code for the Moteino's, Pi, and website (a Ruby on Rails app) are all available on my GitHub
https://github.com/e-carlin/museum_monitoring_sensors.
The sensor Moteino sketch can be found in sensors/pinPowerNode and gateway sketch is in sensors/gateway. We went through a few different wiring schemes and those are available in the other directories under sensors.
I want to thank the community here and Felix for being so helpful and designing such a great product. Myself and my partners had never worked on a hardware project. The knowledge in the forums and on the site was indispensable.
The project is still a work in progress so we are open to any suggestions!
Thank you,
Myself - Evan Carlin (evan+lowpowerlab@carlin.com)
Gabe Lennon (glennon@pugetsound.edu)
Mark Gilbert (mgilbert311@gmail.com
Matt Bogert (mboger@pugetsound.edu)
P.S. Some of us have still not lined up a job after we graduate. If you or anyone you know has a company that could use skills such as these let us know:).