Digital Window Sticker (Arduino Controlled)

Step 6 The Enclosure

As mentioned previously, I am not overly talented with a Dremel.  I urge you to post suggestions on better ways of modifying the enclosure to hold the circuit.  Nevertheless, this is what I did:

Hack the Board:
Start by scoring each end of the Radio Shack Printed Circuit Board (well away from any copper traces), and use a pair of pliers to break away the unneeded side.  When you are done, the board should fit lengthwise against the 6-inch side of the enclosure.

Preping the LED Matrix Displays:
Each of the Display boards has a DIP-switch that controls whether or not the board responds to CS1, CS2, CS3, or CS4.  Make sure the board on the left side of the display (when it is facing outwards) has CS1 turned on, and all other switches off.  Make sure the right-board has CS2 turned on, with all other switches turned off.

Hack the Enclosure - Lid:
The lid of the enclosure is used to hold the LED displays together.  To do this, you need to cut a whole in the lid exactly the length and width of the two displays together.  I cut up a cardboard box exactly the size of the two LED displays, not counting the circuit board they are mounted to, or the other components on the board -- just the size of the LED cubes.  I then placed this on the inside of the lid and taped it in place with masking tape.  I used a box knife to repeatedly score the lid along the sides of the cardboard until the cutout was complete.  I little bit of follow-up shaving with the box knife provided a nice firm fit for the LED displays, with the rest of the board behind the plastic.

Next I put the LED displays in place and used a drill with a tiny bit (3/64) to drill holes through each of the screw holes on the display boards.  (4 per board, 8 total.)

I placed a 4-40 3/4" machine screw in each hole from the top of the lid.  On the inside I secured each screw with a 4-40 nut.  On the top screws I placed a second nut to provide a buffer equivalent in height to the transistors on the boards.

With this in place, each display was back into the lid, with the screws going through the screw holes, and another nut added to hold the boards in place.

Hack the Enclosure - Inside:
Now use some ingenious method (I used masking tape to mark approximate areas) to make slots on the side of the enclosure where the following items can be accessed:

• The SD card socket
• The DC power jack on the BBB
• The USB-BUB pins for connecting the serial monitor to the BBB (for debugging, reprogramming, and simply because they need to protrude if the SD card is going to be accessible, due to my lack of engineering that part in advance. ;)

To do this, I used a Dremel with a cutting wheel.  The resulting slots are much larger than necessary, and not super straight.  I polished it a bit.  I also used a grinding wheel to remove some of the plastic inside the box so that the DC jack on the BBB board is flush against the outside edge of the enclosure.  I found that my DC input jack wouldn't go in far enough otherwise.  NOTE: The cutting wheel on the Dremel cuts, but it also melts the plastic.

I then placed the boards inside the bottom of the enclosure, aligned the DC jack and the SD card socket just where I thought they'd be suffciently accessible, and then used a hot glue gun to glue the board to the bottom of the enclosure.  I also added some hot glue around the DC jack to keep pressure off of the header receptacle when inserting the jack.  I placed a small amount of hot glue on the bottom of the PCB before placing it in the enclosure and quickly set it in place.  I then lined the entire edge of the PCB with hot glue, again, to keep it firmly in place when plugging in the DC jack or SD cards.

Attach the Cable and Lid:
We can now finally attach the ribbon cables that came with the display board.  The short cable should connect the two display boards to each other.  The longer cable can go into the other header box on either board.  (The bus is shared!)  The other end of the longer cable should be plugged into the header box on our printed circuit board.  Make sure you orient the cable correctly so the notch aligns.

Attach the lid to the enclosure and tighten the 4 corner screws.  The Digital Window Sticker is now complete.  If you remove the SD card and power the unit with a 9-volt DC supply through the BBB's DC jack, you should see a message on the display telling you to insert an SD card.

If you don't see the message it is time to pull out your multimeter and verify there are no shorts and that each connection is wired correctly according to the schematic.

Congratulations on your new Digital Window Sticker.  In the next step you'll see how to place images on the SD card.