I recently stumbled across el fabuloso's
DIY auto topoff post and it was so simple, easy and safe that I just had to give it a try. I didn't have all of the parts handy but it only cost me about $20 and an hour to put it together. Here's my stab at it.Parts:
12' of air-line tubing
Air-line couplers (came w/tubing)
Rigid air-line tube
2 Over the door hangers
2 zip ties
2 electric cord screw caps
3/4" float switch FLT015 from Chicago Sensor
1 gallon bottleTools:
Wire cutters & strippers
Black electrical tape
Drill & bits
I started with the switch holder that would eventually hold the switch securely in the 3rd chamber above the return pump. Note that if you do something like this you don't want the switch too close to any motors as it relies on a magnetic reed switch to operate and your motor will interfere with its operation. But my water level is pretty high in that chamber so it wasn't close to the pump.
I took the two over the door hangers and cut them up by scoring a line with the utility knife and snapping the plastic, pretty quick and easy. I also drilled a hole in one of them where I would mount the sensor.
The small L piece I glued to the larger L piece (w/o the hole in it) such that it would hang over the back of the tank just right and not slide around. I mounted the switch onto the other L piece (w/ the hole) as seen in the pictures below.
Next I tackled the lid of the water bottle. The one I bought is just a 1 gallon from safeway, the lid just snaps on. I drilled two small holes in the top and glued the air-line couplers in place. At first I just used super glue but after 10 min it wasn't dry so I ended up putting some marine putty around it, that worked out well.
I then cut a length of the rigid tubing so that it was about an in shorter than the bottle is tall. I cut a 1/2" in or so piece of rubber air-line to connect one of the couplers to the rigid tube, this lets the tube move around a bit without putting pressure on the cap.
Next up was the wiring. I began by splitting the extension cord down the center and cutting one of the lines. I used an extension cord that does not have ground holes so that I would be sure not to accidently cut more than one wire, plus the air pump doesn't have a ground pin anyway. With wire strippers I stripped both ends of the cut extension cord as well as the switch wires.
I twisted each end of the extension cord to an end of the switch wires and used an electrical screw cap to really make a good (and safe) connection. Then I wrapped the whole wad up with a bunch of electrical tape.
Once that was done I used zip ties to attach the two L shaped switch hanger pieces together. I did not make them as tight as possible, just hand tight. This allows the two pieces to slide so that I can adjust the switch position but they are tight enough to ensure no movement when installed.
The final step was simply to attach the ATO to the tank. The switch was placed into the 3rd chamber above the return pump . I put the air pump and water bottle in the stand with the pump above the water. I ran an air-line to the bottle, connecting it to the coupler that was not connected to the rigid pipe. Finally I ran another piece of airline from the other coupler up to the back of the tank, hanging it just above the first chamber.Results:
I'm actually quite impressed with how well this is working so far. The float switch was very easy to position and is very sensitive. It's a real relief not to have to worry about topping off all the time and not worrying about salinity spikes.
The switch itself has a lot of possiblities for mounting, I just happened to have those door hangers that I wasn't using so they worked out really well. In fact the company that sells the switches has a product called mold-a-holder
that is just a thin strip of plastic that you can make plyable by boiling it and the molding to fit the tank, pretty neat stuff.
, I got some great feedback about this design and I totally agree with it all. I'm not happy about having AC run across the little reed switch and having it so close to the water. So I'm going with a slightly modified version using DC power and an aqualifter instead of pushing the water up with air pressure. Stay tuned.
I've since modified my design a little to extend the life of the switch, check it out
Edited by drakkor, 10 May 2010 - 08:33 PM.