3.7 All Together Now
We’re nearing the home stretch. Your hardware should look like the setup pictured in Figure 4, An assembled water level notifier. All that remains is mounting the flex resistor securely and safely in place so that its flexion is accurately detected and not impeded by any obstacles.
The base where the two wires attach to the exposed flex resistor leads needs to be firmly stabilized so that when the water level rises and pushes the bobber upward, the base does not pivot at its fulcrum. If it does pivot, the flex resistor will remain straight and the running Arduino sketch will fail to send the appropriate alert notification. Keep the base stabilized and prevent it from pivoting.
Try using hot glue, heat shrink tubing, or duct tape. If the base still moves, try attaching a small wood chip splint on each side of the base of the flex resistor. Extend the splint length-wise approximately two centimeters above and below the base. Then snugly wrap the splint several times with electrical tape. Tack the top of the splinted base to a small wood post (such as that cut from a typical two-by-four piece of lumber) that spans the diameter of the hole containing the water source.
In the case of a sump pit, you will need to remove the cover of the pit, measure the interior diameter and visit a lumberyard or hardware store that can cut the wood for you. Add an extra centimeter to the cut so that the beam can be wedged tightly as it spans the pit.
Figure 4. An assembled water level notifier
Similar principles apply in the case of a dehumidifier. Instead of using a large piece of wood to act as the mounting base support, use the bottom, pants-hanging portion of an old wooden hanger that can be cut to slightly longer than the diameter of the dehumidifier’s water collection bucket. Mount the base of the splinted flex resistor in the center of the wood support. Depending on the depth of the dehumidifier’s bucket, you may need to raise the base of the flex resistor higher so that the alert doesn’t trigger prematurely when the bucket is only half-full.
Once you’re satisfied with the stability of the mounted resistor, place the bobber and flex resistor inside a small plastic bug, such as a locking seal sandwich bag. This will keep the resistor dry and protected if the water level rises excessively. Run the wires attached to the resistor a meter or more from the measured water source and attach them to the Arduino/Ethernet shield assembly. Power the Arduino using the 9-volt power supply and attach the network cable to the Ethernet shield. Several seconds after you power up the Arduino, perform a quick bend test. If you received the water alert and all-clear messages in your email inbox, then you have succeeded!
Replace the cover of the water containment vessel you are monitoring and wait for your device to alert you to rising water levels.