ELF II LED Matrix Display Assembly Notes
This page documents the detailed assembly notes for building the ELF II LED Matrix Display plugin daughter board.
The ELF II LED Matrix Display adds a 4 digit 16-bit address display to your AVI ELF II, in addition to the 2 data displays. The board uses 3 8x8 LED matrix displays for a larger easy to read display and the Address displays also provide additional messaging when the computer is switched to reset or load. This board is a departure from the period look of the AVI ELF II but it’s a better reading display and the address displays are a welcome addition.
Download the zipped archive of Gerber Files to produce your ELF II LED Matrix Display daughter board. You can send this zipped archive to most PC Board Fabricators to have a set of boards created at a reasonable cost.
You will need to program the two PIC 16F1826 chips with the following listing. Get the Hex listing file here.
Please download the ELF II LED Matrix Display Bill of Materials Excel spreadsheet to help you to acquire all of the components for the board. We have included links to all of the components that we were able to source from known electronics parts houses and have included notes for the components that may be difficult to find.
We suggest that all integrated circuits for your ELF II LED Matrix Display are installed with high quality sockets. We have found that "cheap" turned pin machine sockets have failed us on more than one occasion. If you can't find affordable high quality machine sockets, then we suggest you rely on dual leaf sockets which are rarely known to fail.
Note: The pins on the 8x8 LED matrix displays used on this display board are of a very small gauge and will not insert and seat firmly in a standard IC socket. For our build we soldered the 8x8 LED matrix displays directly to the PC board and recommend doing so but the choice to use sockets is entirely up to the builder of the board.
The easiest way to build the LED Matrix Display Card is to start small and move up. Begin your build with the smallest components and then start moving up to larger components. The entries below detail the order of component installation we have chosen for ease of construction.
Our build methodology begins with installing the 4 resistors. Gather the parts and bend the leads with with small needle nose pliers, then insert the resistors and tape them in place on the top of the board with masking tape to hold them in place while soldering and then remove the tape after the resistors are soldered in place. Solder them as quickly as possible to avoid overheating and damaging them.
The next smallest components to the resistors are the 3 0.1uf capacitors. Insert the capacitors into the board and in a similar fashion to the resistors, use masking tape to temporarily position the capacitors for soldering. Solder the capacitors as quickly as possible so as to avoid heat damage the the components.
If you choose to socket the IC's and 8x8 LED Matrix displays, now is the time to install the IC sockets. We have taken care with the ELF II LED Matrix Display board to orient all IC's consistently. All vertical IC's are oriented with the notch locating pin 1 up and the horizontally installed IC's are oriented to locate pin 1 to the left side. Please take care to install your IC sockets and IC's accordingly.
Note: As mentioned earlier, in our build we have soldered the 8x8 LED Matrix displays directly to the board. If you choose to follow our example, you can install the displays after you have installed the IC sockets.
The next component is the Q-LED. Insert the Q-LED for installation taking care to make sure that it is oriented correctly. Typically, the negative lead of the LED is dignified by the flat side of the otherwise rounded lens and the negative lead is generally slightly shorter than the positive lead. Use tape to hold the LED in place and solder the pins as quickly as possible. LED’s are highly susceptible to heat and overheating an LED can shorten its lifespan or damage it.
The final pieces to install on this board are the four 16-pin headers that connect the LED Matrix Display to the main board. In order to ensure proper alignment of the pins, we pushed the pin headers for the display board into the sockets on the main board and then placed the display board on the exposed pins and soldered them in place.
After you have finished assembling the ELF II LED Matrix display card, check your connections under a magnifying lens for cold solder joints and bridges. Once you are satisfied that the board has no flaws, insert the IC’s and insert the board on your AVI ELF II using the four 16-pin headers and sockets. You can leave the existing LED data displays in place on the main board or remove them. The amount of added current they use is negligible and will not affect the system’s performance.
When you toggle power on the AVI ELF II with the Matrix Display, you will have 4 Address Displays and 2 Data displays. When you toggle from RUN to RESET, the Address display will momentarily indicate that the computer is in reset mode. When you toggle into LOAD mode the displays will indicate that you are in load mode and if you toggle the LOAD switch up while in RUN mode, the display will indicate that you are in PAUSE mode.