On the backside of the acrylic base (Figure 1) are
four pressed-in 2. 5 mm nuts that line up with the mount
holes of a Raspberry Pi. The acrylic base is designed to
have the RaspPi directly mounted and still allow air to flow
around it. Attach the Pi with four 2. 5 mm by 10 mm high
Notice the SD card is to the left and the USB ports
are to the right. Next, attach the RG- 2MtrDrvr
daughterboard to the top of the Pi, lining up the holes and
the header. Use four 2. 5 mm nylon screws to secure the
daughterboard to the standoffs.
Next, attach the stepper motor and the four
alphanumeric displays as shown.
Once the alphanumeric displays are attached, they
need to be addressed according to their position on the
gauge face. There are three solder jumpers on the left side
of each alphanumeric display that are used to set unique
addresses for each display bank. Create a solder bridge
across the pads of A0 and A1 as shown in Figure 2.
Flip the acrylic base over and locate the three
pressed-in 2. 5 mm nuts for securing the gauge face. The
gauge face will line up with these three nuts as well as the
eight standoffs around the outside.
Use three black 2. 5 mm screws to secure the gauge
face to the acrylic base (see the green arrows in Figure 3).
Notice that one of the 2. 5 mm screws is longer than
the other two. This is because it’s used as a needle bump
for the stepper motor; it’s the one just to the left of the
word “Humidity” on the gauge face. Next, press the brass
needle onto the stepper’s shaft; make sure it can rotate to
the needle bump and then all the way over to the max
value of 140.
The next step is to attach the clear acrylic cover with
the eight number 6 machine screws and standoffs
as shown in Figure 3. Once the clear cover is
attached, wrap the LED strip around the outside of
the standoffs; it will fit between the black gauge
face and the clear cover.
You can now tighten the eight nuts on the
back and connect the cables as shown back in
Figure 1. Note the lit pushbutton is also attached
now, but lays loose as it will be mounted to the
back of your case.
The gauge face sits inside the case as shown in
Figure 4 and is secured into position with two
pressure wedges along the sides (the two green
wedges in Figure 4). The lit pushbutton is fished
through a hole in the back panel as shown in
January 2018 31
In our previous article, we discussed the
circuit and code for each of the core
components for the Weather Gauge.
We took a deep dive on how the
stepper is wired up and the node.js
code that drives it. Now, it’s time to put
it all together and light it up!
■ FIGURE 2. Alphanumeric addressing.
■ FIGURE 1. Backside of acrylic base.