@Jerson - Decoupling caps are connected directly across the power pins at the PIC and across the DS1307.

@Henrik, I'll have to search through some old backups as I all the development versions I have are multi-channel.... I still have the original e-mails from DT relating to the project so there is a slim possibility the attachments are still available... I wasn't suggesting the PID routine was buggy, just that whilst I changed the CON setting from 4 to 1 in the main code - strange things were still occurring, and as I wanted 4 routines running at the same time I never thought to test that option..

I'm still getting resets and strange things happening to the clock (even though the clock routine is the same from code that works fine in the current vivarium controller) - like it changes to 08:00 hrs when it reaches 16:00 hrs and 10:00 when turning 17:00 - but so far it's still running the PID routine and has done for three hours now... but I still wouldn't use it to control the heaters !