arduino glitching

hi there
ive made a heating control board that glitches now and then, and resets the arduino any ideas of what could be causing this to happen?
my setup is:
12V from transformer (off load 20volts)
KBP005M rectifier
66 uf capacitor
L7805 volatage regulator
100uf capacitor
0.1uf ceramic capacitor

this might be coincedence but i dont know but when there is just a mains feed on the board with nothing else connected it apears to work fine i did also try when everything was connected a surpresser on the incoming of the board but obviously there are some noisy componenets around such as a fan, ignition transformer, and 2x solenoid valves
any ideas?

Hi, Some info on http://arduinoinfo.info

http://arduino-info.wikispaces.com/RelayIsolation

thanks for that the one thing what stood out for me was surpressing my load anyone know any links that have good information on this

You have a "real" problem here, as in real-world industrial control. Inductive loads like fans and motors produce ginormous amounts of EMI [look that up on wikipedia], and it's worse for AC devices. I've known companies to spend many 10s of $1000 fixing their systems.

First, you need to do what you can to reduce EMI in the switched loads, snubbers are usually the first line of defence. Then you might also need to protect the Arduino power supply from EMI pickup, and also protect all of the I/O lines. The first can require various forms of power supply filtering, and the 2nd may be as simple as voltage dividers or transzorbs on the I/O lines, but may require optoisolators.

This might all be a simple fix, or may take months, depending upon the actual amount fo noise generated in the loads being switched. There is no simple rule for fixing, just a lot of things to try to see what works. Good luck.