PIC, relay and fluro light

pic relay

Hi All, i am tring to turn on a fluro light for my aquarium with pic using a relay. I have got a MCP32016 driving a ULN2803 darlington array, which is then connected to the relay. I have a 1N4004 diode installed across the relay. When i was building my device, i was testing it with just a normal light bulb, but now i have connected my aquarium lights, it looks like the MCP32016 is locking up when it turns the relay on, eg as soon as the fluro arcs for the first time, the relay will turn off, and nothing else will happen untill i reset the system. The PIC still works ok, as i also have a lcd conected, and it will keep updating.

I am guessing this has somthing to do with inrush current, but the relays a 10A, and i am not too sure why it would be effecting the MCP32016 but not the PIC. Both are very close too each other on the board.
Should i have some resistors between the MCP32016 and the darlington array?

Anyone have any idea why this could be happening??

Thank you,

Mark

Resistors as filters can be not as effective as RF chokes ..
Try to implement an LC filter on the PIC's supply line ..
Something like ≈1mH between [+supply] and PIC's Vdd pin and 10-100µF tantalum+100nF ceramic in parallel with PIC's Vdd pin may be a solution to your problem ..

Regards,
IanP

First off, I hope the outputs of the darlington array arent' tied together (the gain of a bjt increases with heat and you will get thermal runaway when a bunch of bjt's are paralleled.) Second, I assume you are going through a ballast made for the tube, and are not trying to drive it directly, as flourescents require huge voltage levels to turn on hence the use of ballasts. Is the ballast working, have you tried another light? Last, try an optoisolator for the micro output. It may not end the problem of the relay cutting out, but it may stop the micro from resetting.
Other than that, I can't be any more specific.