The remote display is optional. I’ve created Node-RED flows that replace the functionality of this display. This provides a less expensive option for starting with CTR2. More information on Node-RED can be found in this post.
In this post I’ll describe the process of building the remote display driver board and enclosure.
Before we start, let me mention that the 5″ display used in the photos in this post is a Nextion Intelligent series display. The PCB on these displays are red (and they look pretty sharp 🙂 ). After these photos were taken I found out that the Intelligent displays use 5 VDC logic levels, not 3.3 VDC as the Enhanced series do. This makes them incompatible with the 3.3 VDC RS232 chip I use on the display interface board. Make sure you order an Enhanced series display when you order your display!
As mentioned above, the serial port on the Nextion display uses 3.3 VDC logic levels. This is all well and fine if you plan on mounting the display close to the HMI board (in fact there is a header on the board to allow this). In this project I chose to mount the display away from the HMI. This required converting the 3.3 VDC levels to something that could extend the serial port’s range. I chose RS-232 mostly for it’s simplicity.
I also needed to extend the rotary encoder signals since it is mounted in the display’s remote enclosure too. So with the two data lines, +5 VDC, ground, encoder A, B, and Switch signals I needed 7 wires.
On the original prototype I used DB-9 connectors and a standard DB-9 serial cable to connect the HMI to the display. This worked fine but by modern standards those connectors and cable are HUGE! I changed the design to use RJ45 jacks and CAT5/6 cable. I’ve tested various lengths of CAT5 cable and haven’t had a problem out to about 20 feet. If you have problems try CAT6 cable – it has larger conductors.
The Display RJ45 jack on the HMI board is mounted on the front-right of the board. The microphone, headphone, key, and PTT jacks are also on the front. DO NOT confuse the Display jack with the Radio I/O RJ45 jacks mounted on the Auxiliary or RJ45 Switch boards. These jacks are on the back of these boards facing the rear.
The Display interface board is supplied completely built and tested. It also includes the M3 6mm+6mm standoffs, M3 nuts, and M3 screws to mount the board in the wedge enclosure.
In the photo above J2 connects to the four wires supplied with the display. Install them in the color order shown (Black=Ground, Yellow=RX, Blue=TX, Red=+5 VDC).
CAUTION! These connectors are not keyed. It is entirely possible to roll the +5 VDC and Ground wires and burn up your display. Be very careful wiring these connectors.
J3 connects to the rotary encoder. The encoder has 5 pins. The two pins on one side go to the N/O switch. The three on the other side go to the encoder’s A, Common, and B contacts. Click here for more information on how rotary encoders work. Use the four 4″ Dupont female jumpers supplied with the Display interface board to wire the encoder. Connect them to the encoder as shown below. The wire colors supplied with your board may not be the same as shown here. Use the colors in your kit to identify the sequence of wires between the encoder and the display driver board.
Note that you’ll need to install a jumper from the ground side of the switch (small blue wire in photo) to the center terminal on the other side. This is the A/B common connection. I used a short piece of blue wire-wrap wire for this.
Use heat shrink when you connect the Dupont wires to the encoder. The Dupont wires have thick insulation but small wire so they need this extra support.
This completes the electrical construction.
I designed a simple wedge shaped acrylic enclosure to mount the display and encoder in. The face is sloped 33 degrees and the panels interlock using tabs and slots. Building it is as easy as “insert Tab A into Slot B”. A completed enclosure for the 5″ Nextion display is shown below.
I cut the panels on my Shapeoko 3 CNC router and snap the pieces apart before shipping them. I do not do any finishing or burr removal. You’ll need to do this before assembling them.
If you want to cut your own, visit the Files: Display Enclosure CNC Files post.
To remove the small burrs from the tabs used to support the panels during routing, lay a piece of 220 sandpaper on a flat surface and lightly sand each edge.
You’ll also want to lightly sand around the display bezel cutout.
Because the panels are cut with a 1/16″ router bit the tabs have rounded inside corners. The acrylic panel is on the right with the small flakes of acrylic on it. The curvy looking cuts are due to camera lens distortion.
Use a small flat file to slightly taper the tab and square up the inside corner so the tab will fit snugly and flush in the slot. Don’t take too much material off!
When done the tabs should look like this….
Before gluing the panels, first assemble the enclosure to make sure everything fits.
In the photo below the base is positioned with the front beveled edge facing to the right. It is CRITICAL that this beveled edge faces up as shown. The display board mounting holes and notches for the back panel’s tabs are on the panel’s left.
The side panels are positioned with the back panel notches on the rear and the circular cut facing the front. Two tabs on the long slope face upward.
Next, snap the top and back panels in place. Note that the top panel has bevels on its top and bottom edges. Both bevels must face up. If you put it on upside down the encoder will be on the wrong side and CTR2 label will be reversed. The bottom edge of the front panel should lay over the bevel on the base panel. The back panel also has a beveled edge. It should lay under the top edge of the top panel.
Once you’re happy with the fitment, disassemble the panels and arrange them so you can put them back together correctly. We’ll reassemble them with glue next.
For best results, use ‘gel’ type CA glue (Super Glue), not the thin type. Don’t use too much as it causes a slight smoking effect on the acrylic. Also, be careful not to get any glue on any of the surface faces as you work because you won’t be able to remove it. Epoxy glue can also be used.
A very small dob of glue in the corners of each tab is all that’s needed. It also makes it easier to disassemble the enclosure if needed.
Install the two side panels first. Temporarily install the back panel to keep the side panel at 90 degrees while the glue sets. Do not glue the back panel in place! Hold each side panel in place for about 60 seconds while the glue sets..
Once the two side panels have been set, add a dob of glue to each inside corner of the four tabs on the sloped edges of the side panels and snap the top panel on. Allow the glue to dry for several hours.
If you want, you can also add a little glue to the beveled edge where the top panel rests on the base panel. I generally don’t do this because of the smoking effect from the glue.
If you want to paint your enclosure, mask off all of the exterior surfaces and use a can of spray paint to paint the interior surfaces. This will leave the shiny acrylic surface outside and protect the paint from scratches.
To finish the display, first install a CR1220 battery into the display’s battery holder. This battery maintains the real-time clock in the display. Next, connect the display and encoder to the display interface board then mount that board to the base panel using the hardware supplied. Bolt the standoffs to the board using the threaded male end of the standoffs and four M3 nuts. Next, use the supplied M3 screws to mount the board to the base panel (so the screw heads are on the bottom of the base panel). Mount the display using the four M3 6mm+6mm standoffs supplied with the enclosure kit using the same technique (so the screw heads are visible from the front). Mount the encoder in its hole and tighten the mounting nut. Finally, attach the four silicon feet supplied in the enclosure kit on the bottom of the board.
You can use any 1/4″ knob. I found this one at Radio Shack.
When you’re ready to install the rear panel, use a couple of small pieces of clear tape or a couple of really small drops of CA glue to hold it in place. If you chose to glue it on, you’ll need to break those glue locations to remove the back panel in the future, so make them small!.