Arduino & ethernet shield - enviromental interferance in operation

Hi, Does any body have experience of an Uno and Ethernet shield in use in a hot enviroment. Also what are the known succeptabilities of this kit to to RF interferance.

I’ve built a thermal controller for my solar/thermalstore/gas boiler/back boiler set up and I’m getting some weird ‘hang’ and partial ‘hang’ failures. The controller is in a small room with the thermalstores and the ambient temperature is 26 to 30 degC. It is also about a meter from a TV distribution amplifier (uk frequencies) and a WiFi hub.

The set up uses PT1000 resitance temperature probes (for compattability with other things) to measure assorted temperatures in the system and makes decisions on which valves to open/close etc. The info is stored on an SD card and can be read off to a desktop over an ethernet link using some HTML which is also stored on the card. It is also possible to set various parameters that the Uno uses via another piece of HTML.

I’m seeing three things:-

a) The binary ouput of the analog to digital conversion of the PT1000’s is jumping about all over the place even when subsituting a straight 1000ohm resistor for a probe . The variation is about +/- 3 bits. The lines from the probes all have decoupling capacitors as does the reference divider.

b) Some times the whole thing hangs for no apprent reason that can be monitoted either on the serial port or the ethernet or a volt meter.

c) Some times just the ethernet hangs. The web browser on the desktop just sits there waiting for info from the Arduinos IP address, ocasionally, refreshing the page in the web browser works but most times the only way to resume communication is to reboot the Uno.

I’ve updated to the 1.0.1 version of the IDE so its not the fix that you had to put into the ethernet.cpp file. The whole thing works fine on the bench in the workshop, but it has to go in the Tank Room to be wired up to the sensors and that’s where the problems start. I’m beginning to think in terms of enviromental interferance but I’m not sure how you track that down and deal with it.