here's my DIY PVC float switch for my ATO
This PVC Float switch is very easy to make and takes less than an hour to construct. Materials are simple and can be easily acquired.
I wont list down the materials i used since these pictures will speak for itself.
Here's the design done in google sketchup:
3D View:
X-ray View:
Internal Mechanics View:
This is how the switch works:
- when the water level is normal, the 5Cent coin is not in contact with the thin metal sheet
- as water evaporates, the styro floater goes down, until the 5Cent coin comes in contact with the thin metal sheet
- when contact occurs, the pump in my water reservoir activates. it then pumps water into the sump
- when enough water is pumped, the styro floater rises again, thus cutting contact of the 5Cent coin from the thin metal sheet
** note that there is a marble embedded inside the styro floater. the purpose of this is to create a "Heavy Floater". a floater that is heavy enough to pull the switch down, yet buoyant enough to lift the coin up even small amount of water is added.
** the "play" or distance the the coin travels up and down is less than 0.25 or 1/4 of an inch. the less play you have, the more sensitive the switch becomes.
*** PLEASE DON'T FORGET TO SEAL THE MIDDLE PART OF THE PVC TEE (WHERE THE WIRES COMES OUT) - THIS IS TO AVOID MOISTURE FROM GETTING IN, THUS PREVENTING ELECTRIC SHOCK. I SEALED THIS ONE WITH A THIN STYRO SHEET (SHAPED LIKE A COIN), THEN LOCK IT WITH A THIN PVC RING INSIDE THE TEE, THEN HAVE IT BITE THE RIM OF THE SUMP
Here are the photos of the actual working model. This was installed in my sump since January 23, 2011 and its been working fine. It activates after about 1 liter of water loss.
Top view with top end cap removed:
Enjoy and happy DIYing!!
kidding aside... galing mo sir! this is a big help to both the aquarist and his pocket. 
