I have a circuit set up to detect water using a Darlington pair transistor and a S-R Latch, well actually I'm using 4 of them for redundancy. The latched outputs from the 74LS279N are tied the Duemilanove. My problem is that any little thing seems to set them off. If a large load in the house starts up (AC, fridge, cheep fluorescent light, ceiling fan etc...) it trips the circuits and set's off my code. Also if for any reason somebody touches the ground of the circuit like the mounting screw for the LCD or similar contact, it will trip the circuit just like the noise through the power supply.
If I run it off of a 9V battery to test, it's completely fine with the noise from the power in the house, but it's still sensitive to people touching the ground of the circuit.
I'm currently using a cheep 9V supply (http://www.sparkfun.com/commerce/product_info.php?products_id=298) I guess I can use a PC supply and run the 5V into a spliced USB adapter for a more regulated supply, but that's kind of bulky. But hey if that's the best option, then I'm in. But I don't know if that would solve the ground problem.
Here is the sensor circuit, just the same circuit 4 times over with the reset tied to all of the latches for easy resetting.
Any help would be great, thanks.