Guy's, this is probably aimed at DT or Henrik as they are really familiar with my thermostat project, but I'm open to suggestions.

My prototype thermostat unit (details can be found at http://www.picbasic.co.uk/forum/showthread.php?t=12712) has been running now for around 6 months, but recently I've had two incidences where the unit appears to be running, but has actually locked up in some way, after I tried fixing a problem with a light that is driven from the unit.

The first instance the light was out, so whilst everything was still running I detached the cable and reseated the tube then plugged the light (an under cabinet florescent T5 tube) back in. Everything seemed OK until I noticed the snake in each vivarum move right up the cold end of the enclosure. The temperature on the LCD still showed 33.1C and both LEDs were pulsing away as normal, but on opening the viv the heat was obvious. I reset the controller and off went the alarms as both vivs were running at 45c (which was now shown on the display).

The second instance was the same, but this followed a simple tapping of the tube to get it to light. Only this time I noticed that the temperature readings from the DS18B20's didn't fluctuate (normally they are constantly changing every few seconds by +/- 0.1c).

It is as if the program in the chip stops running the PID loop or something but where you would expect the LCD to blank out, or the LEDs to stop pulsing if the chip stopped running that doesn't happen. Could it be the fuse settings? Can a PIC go into a state of limbo like this ??

I've been told that some of the commercial companies hang out on the reptile forums have got wind of my project so I don't really want to paste up the current version of the code in full, so PM me if you need the files. I can obviously post up spinets, if required.

Comments please