Step 6 : Connections

Now connect two cat5 cables on the side of the board to the 16 anode rows. Make sure you use a pattern to keep the order the same. Start at the top this is row one. Go 1 - 8 with the first cat5 and repeat the same pattern for 9 - 16. Make sure you cables are long enough to reach where you’re going to mount the controller to the panel and connect it. Now do the same for the cathodes by connecting to the cathodes along the bottom of the panel start at the left side facing the front of the panel. Make sure you use the same pattern. If white/orange is #1 always make it #1. This will take 6 cables as there are 48 columns.

Step 7 : The controller part 1


The controller is a one off design I came up with for this project. Do not use the images on this how to create your board as it has had fixes made since the screenshots were made. The ExpressPCB file is current. This controller is really two different sections and I will talk about each separate. I was asked to explain the operation more than I did on my last how to so first how it works.
The first section is the driver section. The board really is just 48 Led’s as far as the controller knows. But we turn power on to a different 48 each time in sequence this allows us to drive 768 led’s with 48 channels. The driver receives the same signals the rest of the controller does. The clock, and latch signals. But it gets different channels of data than the other section. it gets the lpt ports data line 2,3,4,5 from my program on each of the sixteen passes it takes to draw the graphics sends 1 of 16 combinations of 0's and 1's on these ports. 0000 is zero or row 1. 1111 is 15 or row 16. When the control chip (74hc4514) on the driver gets this info clocked into it brings the matching output high. All 16 of these channels are connected to there matching control port on one of the driver chips (ULN2074B). While the controller chip is smart enough to know what channel to turn on it can not handle enough power to run the led’s so the driver chip does. Each of the four have transistor that can supply 1.5 amps. These then power up their matching row on the panel so we have power to light the led’s.

Step 8 : The Controller part 2

When my software clocks the data into the first section to power up the correct row it clocks in the data that it has sent to the second section. So we now have power on that row we need to pick the led’s on that row to light. This is the job of the three MBI5027GN chips. It works just like a 595 chip on the 595 controllers but its 16 bits so 16 channels each. Three give us our 48 channels. Data is clocked into the first chip and flows to the next and then the next. Once 48 bit have been clocked in we latch it to set the output either on or off. if on it will provide a ground for that column of led’s. If off it is open and will not let power flow. Since we have power on one row we turn on the columns for the led we want to light on that row. Remember the latch is the same signal we used in the driver section so when we latch it means we ground the columns we want on and we power up the row we want all with one latch signal. The MBI5027 is able to sink 90 ma per channel and at any given time only one led is powered per channel so we have plenty of current to run the led. This happens on my machine at 90 hz or 90 times a second far too fast for you to see. The rate at which it updates is dependant on your computer and lpt port speed but anything reasonable should be able to keep it above the 35 - 40 hz you need for it not to flicker.

Step 9 : Parts

You need the following :

4 ULN2074B Mouser pn 511-ULN2074B
1 74HC4514 Mouser pn 512-MM74HC4514N
4 .1 uf cap Mouser pn 581-SA105E104ZAA

3 MBI5027GN

Sockets if you want them.

you can't get the MBI5027 from mouser so I got mine from
http://www.kingelectronics.com/index.asp?action=product&id=166
Make sure you call and order the GN version 24 pin dip.

There are no fancy connectors because of space the cat5 cables can either be soldered directly to the board or come up with you own design of connection. If we ever coop the board I would make it larger and add rj45 connectors.

The Board design can be found as a expresspcb file at http://putstuff.putfile.com/55289/2147248

Step 10 : data connections


In the top right corner of the controller board you will see a number of pads. the left set looks like a "L" and the right set looks like a mirror of the same "L". The in side is the left side. From you computer port the top pad of the "L" should connect to the gnd on your computer port which is one of the following pins 18-25. The next pad below that one should connect to the clock signal from you computer or pin 1. The next pad down is the data for the columns and should be connected to pin 2 on your computer. the next down is the strobe signal and should hook to you pin 14 on the port of your computer. The leg of the "L" is the data for Rows. The left most one should be connected to pin 3 , the next pin 4 , pin 5, and then pin 6 for the last of the four. The backwards "L" is for the next controller if you daisy chain them and the connections would flow the same to it from these pads. The last connections here is the GND and +5v connection just to the left of the other connections. Make sure you provide your power here and use appropriate gauge wire. The system can pull up to 4 amps so take that into consideration. Do no try to feed the power through the cat5. It will cause issues with distance by adding noise to the data and it's too much current to be pulling through cat5 in my opinion.