I think I must have read almost every page on this site when I discovered it. I really loved this idea. For ages I've wanted to monitor and interact with my surroundings via some home automation solution, but all the commercial solutions are really expensive and limited. MySenors and OpenHAB really give me the customisation I want.

The only thing missing was putting everything together. I'm working on that. But first I needed to create my sensors, as small/cheap as possible and battery powered.

Here's my first pass at building the temperature sensor, in a 3D printed box which also houses the battery compartment.

The circuit board (Single Sides Etch) slides in on groves in the walls. I added the battery monitoring to the Arduino as I really need to know if/when the batteries are going flat. That's all pushed back to openHAB which I can then create a rule to watch for battery low, however so far the batteries seem that they will last for ever!

The contacts on the battery box are small flat metal. Aluminium between the batteries, and Copper for the terminals. I used copper as I could more easily solder to it.

Making it very easy to assemble.

I've built an ethernet gateway from scratch.. using the ENC28J60 Ethernet module and NRF24L01 Radio. I loaded the MQTT gateway into my ATMega268 and started it going...

For the first few hours everything is working perfectly. I can see it receiving updates from the the sensors (Temperature for the moment), and sending it on to openHAB. I can see a TCP connection on the OpenHAB server and all will be well.

After 3+ hours though the MQTT will still be receiving traffic from the sensor but will stop Ethernet communication and not send it onto OpenHAB. I suspect it's a overflow issue somewhere.. As soon as I reboot the MQTT gateway all is well again.

I've seen a few people report issues similar to this and discussing a watchdog to reboot the MQTT if it fails. I'd rather not do this though, and better to find the underlaying issue. I also read that not all the ATMega support it.

Sure here you go..

TempSensorBase.stl

TempSensorTop.stl

And now in it's 3D Printed case..

I was still seeing it stop working. However after further diagnostics it seems the issue lies with the ethernet side of things, the Arduino and Radio still continue to function.

I tried to use the Arduino to reboot it's self, which didn't work, but also would not have rebooted the ethernet modules and thus would not have solved this.

I've ended up building a 555 timer circuit which is triggered from the Arduino (Digital pin 3), the time fires and triggers a relay to remove power from everything for 2 seconds. Thus we end up with a complete reboot.

Here's my circuit diagram, take 5Volts directly and then PWR is fed into my previous circuit that way when the relay clicks over all power to the Arduino and ethernet is removed.