Creating the PVC housing

We bought schedule 80 dark grey PVC from McMaster-Carr to create the housing. The parts consisted of a female end cap with NPT, a 1 foot section with male NPT on one side, a 3 foot section with male NPT on both sides, a female to female coupling, a 1.6x6x6 inch block of schedule 80 PVC, a 2 foot long corner of pvc, and a .25x6x6 inch block of pvc.

We used the 3 foot long piece to house the electronics. To get the electronics to stay in place we created a stand using 3 threaded rods which we attached to a bulkhead using a tap and dye. We made triangular pieces of pvc out of the .25x6x6 block of pvc which we also tap and dyed so that they could be threaded onto the 3 rods and hold them together. The triangular pieces were equilateral triangles that were 2.5 inches long on each side with rounded edges so that they could fit inside of the pvc pipe. To hold the Arduino boards onto the threaded rods we used 2.4 inch sections of the corner and tap and dyed them so that we could attach those pieces to the threaded rods and to the Arduino itself, using nylon screws and nuts. We put the nylon screws through the premade holes in the Arduino; some of these screw will not fit perfectly and the heads of the screws will have to be ground down on one side to fit correctly. You can see the threaded rods going through the triangular piece of pvc on the left side of the image below, and the pieces of pvc corner holding the Arduino boards onto the threaded rod in the middle of the image. 

Threaded Rods and PVC Corner

We had to grind the edges of the corner section down to fit inside of the pvc pipe. Make sure the holes are all equidistant from each other on each of the triangles, because if they don’t lineup right the threaded rods will have to bend, and will become more difficult to thread.

The 1 foot piece of PVC houses the sensors. We cut four 1.5 inch wide and 7 inch long holes in the side of the PVC to allow water to flow through this section and pass by the sensors. The threaded end of the 1 foot section of pvc will have a pvc bulkhead glued in place which has the sensors screwed into it, the other end has another bulkhead that is screwed in place. A screen will go around this unit to keep the mud out and allow the water to flow through it. Below is an image of the 1 foot section of pvc coupled together with the 3foot section.


The coupling connects these 1 foot and 3 foot pieces together and the end cap goes onto the 3 foot long pipe to seal one end.


The block of pvc we gave to a machinist to create 4 circular bulkheads to fit into the ends of the pvc pipe, 1 of which we mounted the thermistor,pressure gauge, and conductivity sensor in, and the other we attached to the bottom of the 1 foot section (and the last 2 are extra’s.) You may want to get a slightly bigger block as we cut it a little close on the bulkheads and some of them were not perfectly round because of it. In the image below you can see the screws holding 1 of the bulkheads in place on the right side of hte screen, and on the left side of the screen you can see the sensors sticking out of the other bulkhead which was pvc glued in place.


To drill the holes for the pressure gauge and conductivity sensor we first drilled a small hole and then slowly went up in drill bit size until we reached (___.) Make sure these holes do not overlap with the threaded holes for the 3 legged stand. For the thermistor we made a slightly larger hole in the top section of the bulkhead for the sensor to screw into and smaller hole in the bottom section to fit its thinner section. After drilling out and tapping the bulkhead to fit the sensors in, we used pvc cleaner and glue to attach it permanently to the one foot long section, on the threaded end. Make sure you quickly and deliberately put it inside the 1 foot long section because pvc glue will attach the two pieces permanently together very quickly.

To make the connections between the sections of pvc watertight, I used Real-Tuff sealant. It is a non hardening sealant that makes a waterproof seal on threaded pvc pipes. It does not leak a drop, the only problem is that I will have to reapply the sealant every time I unscrew the cap because unscrewing it removes the watertight seal.