into the enclosure, then the wires were connected from the
board to the jack. The enclosures were machined using the
respective machine labels that are available at the article
Measure the center point of each side of the
enclosure. The machine labels have center lines that are
used to align the labels with the enclosure. The same must
be done for the back panel of the pressure unit. The
pressure unit has two labels: one for the enclosure front
and one for the back. Both the switch and LED holes for
the front of the enclosure and the holes for the
adjustments and the pressure tube for the back panel are
shown on the machine label as an X-ray view. The mirror
image label is for the back of the enclosure.
Again, the actual labels used on the enclosure are
Since they are jpg files, you can use any photo program
using the dimensions of 3. 5” wide by 2. 5” high for the
labels, and 3. 5” wide by 2. 7” high
for the machine labels.
Several different types of
electrode assemblies for the ionic
level controllers were built and
tested (Figure 7 A/B/C). One
electrode probe (Figure 7A) was
made using one inch and 1.25”
diameter PVC pipe. The 1” pipe
was used as a mounting shaft, while
the 1.25” pipe was cut into two .75”
rings used as the adjustable
7The .75” rings were drilled
and tapped with a 6-32 thread to
accommodate a . 5” x 6-32 nylon
pan-head screw that is used to clamp
the rings to the mounting shaft at the
desired liquid level.
Two .0625” holes were drilled through the wall of the
rings to mount a 14 AWG copper wire used as the sense
electrode. The 20 AWG SPT-1 lamp wire was soldered to
the copper sense electrodes, then run up the mounting
shaft through a third ring at the top of the mounting shaft.
This kept the wires taut along the shaft. The assembly
worked fine, but seemed bulky and difficult to make.
A second version (Figure 7B) was built using a . 5” and
.75” diameter PEX tubing. A smaller 24 AWG speaker wire
was used as the sensor wire. This assembly was much
smaller, less costly, and worked fine too. The rings were
machined like the PVC pipe and took some time. A third
electrode assembly (Figure 7C) was built using a . 5” PEX
tube, 24 AWG speaker wire, and three nylon zip ties. This
was the easiest to make. The only trade-off was that it is
more difficult to adjust the liquid level height. Since the
liquid level height adjustment only has to be done during
the initial setup of the system, this is not too much of a
problem. My preference is either
version B or C.
The pressure based level
controller required a sense tube to
capture the pressure caused by a
rising liquid level (see Figure 8). For
testing and development, a . 5” PVC
pipe was used. The bottom was cut
off at an angle to allow the liquid to
enter even when the tube was
inserted to the bottom of the tank (in
this case, a five gallon pail). A . 5”
PVC pipe cap was drilled and
tapped for a . 25” NPT pipe thread.
A . 25” NPT to .125” barbed elbow
was threaded into the PVC pipe
cap using Teflon tape to ensure an
26 December 2016
■ FIGURE 7.
■ FIGURE 8.