The work described in Part I was accomplished at my desk in Wyoming. We brought all of the components to Florida and installed them on Sea Gator. The final assembly and installation process are reported here.
Building the Water Tank Sensor
When the remote display and tester were completed it was time to build the sensor for the water tank. We have two 75-gallon stainless steel tanks. Because the tanks are connected to each other via an equalization hose near the bottom they should always have approximately the same water level. So I only need a sensor in one tank.
Each tank has a 10-inch diameter stainless steel inspection plate on its top. Rather than drill a hole in an existing steel plate I decided to create a new plate from 1/4-inch unbreakable polycarbonate. I made a template of the existing plate and its hole pattern, which I used to cut the polycarbonate (and I preserved the original inspection plate for just-in-case).
As a bonus, the clear polycarbonate provides a backup should the sensor fail: I can simply shine a flashlight through the new transparent lid to view the water level inside of the tank.
Next, I used one-inch PVC pipe to build the sensor structure, shown in the photo above. I drilled holes for stainless steel machine screw sensors and I partially drilled larger diameter holes to create flat surfaces for rubber and stainless washers. Although it's not necessary, I will attempt to create a water-tight sensor initially (if my sealing techniques fail, I will simply drill holes in the bottom of the sensor to allow the water inside the PVC tube to reach an equal level with that outside tube). I soldered ring terminals to the common lead and to the six individual sensor leads, depicted in the photo above.
To connect the wires to the RJ-45 jack, I used a small breakout board from SparkFun Electronics. The breakout board is only slightly larger than the jack and fits within the PVC fitting I will use to connect the pipe to the polycarbonate plate. I soldered the RJ-45 jack and the sensor wires to the breakout board, shown in detail in the photo (left).
Next, I assembled the sensor by taping the stainless steel machine screws in the ring terminals then sliding the assembly inside the PVC pipe. It was a bit of a challenge, much like assembling a model sailing ship inside a bottle. I created my own "grabber" tool using 12AWG solid copper wire with a bent loop hook end inserted into 1/4-inch plastic tube. With this tool I could push the copper loop out of the little tube, insert it into the PVC pipe, hook a machine screw then push the tube to firmly grasp the machine screen so I could position it within the proper pipe hole. I sealed the machine screw and threads with silicone before securing with washers and nuts.
I then used PVC glue to secure a cap fitting on the bottom of the sensor pipe and used epoxy to secure the breakout board in the top coupling. A gasket on the coupling and a threaded cap fitting with a hole for the Cat5 cable secures the pipe to the inspection plate. I used machine screws to fasten four aluminum braces to the pipe and plate for additional support.
The picture (right) shows the finished sensor assembly. In the photo, white protective film still protects the polycarbonate; I removed it before installing.
I replaced the deteriorated black neoprene inspection plate gaskets with new gaskets that I cut from white 1/4-inch closed cell foam. The white gaskets and PVC, stainless and aluminum have a reassuring sanitary appearance near our water supply. See the finished installation, left
To complete the installation, I connected a Cat5 cable (the white one on the left) to the sensor then routed the cable through the back of my nearby nightstand and into the adjacent hanging locker. I connected the cable to the remote display, which I will store on a shelf in the hanging locker.
Whenever we need to check our water level, it is a simple matter to open the hanging locker door and flip the switch on the remote display (photo, right). Later, I may consider a more permanent and visible location for the display. However, checking our water level is not likely to be a daily event - considering we've never checked it before - so we'll give it some time and see whether accessing the remote display in the current manner will suffice.
It will take the test of time to determine how well the sensors hold up after a season immersed in the tank but the system will be simple to inspect and clean.
This was a fun project and a nice addition to Sea Gator. We no longer need to guess how much water is in our tanks and we can shower ("Lather, rinse, repeat") without uncertainty.