LedTriks Controller Assembly Instructions
Background
While there are a myriad of computer based controller hardware available that will run under the Vixen software for controlling Christmas lighting, there were no LED display panels that could be controlled thru Vixen. Robert Jordan decided that the Vixen community needed a LED sign and took it upon himself to design and prototype an LED scrolling board. While Robert had seen LED boards everywhere, he wanted on that allowed you to do text and animation. He envisaged a LED display board that could be your show sign and a place for animations during the show.
Why LEDTRIKs? When Robert first announced the concept of the board he was working on to the Vixen Forum, some suggested to Robert that the board would allow users to perform tricks with LEDs aka ‘LEDTRIKs’.
Circuit Diagram
The circuit Diagram for LEDTRIKS is linked here. Schematic Diagram V6.0
The circuit is based on three MBI5027-GN-5027 16 Bit Constant current LED Sink Driver Integrated Circuits. The PC is connected to the LEDTRIKS via the RJ45 connector IN. You will need to assemble an interface cable to connect from the PC to the IN socket on the LEDTRIKS controller. The cable details are specified in the Building the Interface Cables section.
The board can be what every size you like. The LEDTRIKS Board can control a single 16 x 48 LED board and up to 4 boards can be connected together – side by side.
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Shown above (TBI) - LEDTRIKS Board Configuration Examples are the standard configuration – 1 panel wired in a 16 x 48 LED pattern and one of the optional configurations – 2 panels and two controllers wired ix a 16 x 96 LED pattern. As the software is configured at the moment (pre-release), text and animation will be able to scroll across a 1x1, 1x2, 1x3, or 1x4 panel display.
1 Jun 2007. KC is looking into a change in the software to allow a 2 x 1, and up to 4 x 1 configurations.
The PCB design (version 6 – public BETA) is the current version of the LEDTRIKs design and has been configured for Vixen control and up to four boards can be cascaded.
Driving the LEDTRIKS LED Array
Hardware Elements
There are two main elements of the controller. One is a 48-bit shift register (three cascaded MBI5027 chips, which is similar to a 74HC595 chip followed by a ULN2803 chip) used to control the cathodes of the display (each output controls the cathodes for one column of the display). The other is a 4:16 latch/decoder (MM74HC4514 chip) used to enable the anodes for one row of the display.
The control signals (8 wires plus ground) are as follows:
1) An overall display inhibit signal. This signal unconditionally turns the LEDs off when it is high, allows normal operation when low.
2) Four dual-purpose data signals. These signals are bussed to all of the controllers that are connected to a parallel port. All four signals are connected to the data inputs of the latch/decoder mentioned above, to select 1 of 16 anodes. Each controller has a jumper array to allow one of these data signals to be used as the serial input to the shift register mentioned above (each controller should have a different bit selected for this function). A '1' in the shift register will enable the associated column in the display; a '0' will disable the associated column.
3) Clock for the shift register. Data is clocked into the shift register on the low-to-high transition of this clock, although it won't appear on the outputs until the shift register output latch is strobed.
4) Latch enable (strobe) for the shift register (normally low, pulsed high and then low again to cause shift register data to be copied into the output latch).
5) Latch enable (strobe) for the latch/decoder (normally low, pulsed high to capture new data in the input latch).
The following procedure should be invoked at 16 times the designated refresh interval. As an example, if the entire display is to be refreshed 60 times per second, this routine should be called 960 times per second (16 rows/display_refresh * 60 display_refresh/sec). Each consecutive call to this row_update routine should select a different row, so that all 16 rows of the display are refreshed at the same rate. It is best if the rows are refreshed in some sort of random order, so that it will be more difficult for the viewer to notice any flicker. One way to do this is to have a 4-bit bit counter, and reverse the order of the counter bits to select which row to refresh.
1) For the selected row of pixels, transmit 48 bits of data for each controller. The data for multiple controllers is sent in parallel, with data for controller 1 sent on bit 0 of the data port, data for the controller 2 is sent on bit 1, and so forth. The clock line has to be pulsed high (and then low) while data on the data port is stable (so there will be 48 pulses on the clock line). This is basically the same procedure used in controlling the Olsen 595 board.
2) Place the row address on data bits 0-3 of the parallel port data register.
3) Inhibit the Display (and leave it inhibited for the next step.
4) Take both strobes high and back low again (while the row address is still on the parallel port output lines).
5) Enable the Display.
6) Determine which row to display next. See the note above about reducing flicker.
The driver program should inhibit the display when it exits. Otherwise one row of LEDs will be left on continuously at full brightness, which looks bad and is not good for the longevity of the LEDs.
Components
The parts List for the LEDTRIKS is fairly basic.
Qty Supplier Part# Description
1 Mouser 512-MM74HC4514N Multiplexer/decoder chip
4 Mouser 511-ULN2074B Driver Chip
3 Digikey A6279EA-T-ND Allegro A6279 ***
10 Mouser 571-5202514 RJ45 Modular Jack
4 Mouser 571-3902614 16 pin dip socket
4 Mouser 581-SA105E104Z Ceramic cap
4 Mouser 571-3902618 24 pin dip socket
1 Mouser 538-10-89-7081 4 x 2 Pin DIP header
1 Mouser 649-65474-002 Shunt Tin
1 Mouser 538-50-57-9402 2p Sl Conn
1 Mouser 538-70543-0001 2p sl conn fem
2 Mouser 538-16-02-0102 term bulk sl conn
1 Mouser 604-WP7104EC Led Red
1 Mouser 660-cf1/4c471J 470 ohm resistor
3 Mouser 660-CF1/4C102J 1k Resistor
- While the Parts List shows the Allegro Part, you can use the MBI chip. Please note that the MBI5027-GN chip must be the GN suffix. This is a 24 pin DIL package. There are other IC packages available; however you can only use the GN with this PCB.
You are also going to new at least 768 LEDs, I have purchased a bag of 1000 LEDs from www.besthongkong.com. The price was $19.99 plus shipping. The Part / Model: BURC333W20BA04, 333 5mm Ultra Red Series LED .
They also sell a handheld tester for LEDs for $9.99. This is a great way to test the LEDs BEFORE installing them into the panel.
Assembling the Circuit Board
Assembling the circuit board should be fairly east for most hobbyists. Start by checking the PCB over for any production faults. Ensure that none of the copper tracks are shorted or open and that the holes are clear of obstructions. All the boards I have made are electrically tested at manufacture so there should not be any problems!!
You will need a fine tip soldering iron and a high quality solder (tin/lead mix or Lead free). I use a temperature controlled soldering station and a 0.8mm solder with a rosin core. The first batch of boards is not ROHS. All subsequent boards are ROHS and can be identified by a YELLOW silkscreen, rather than the WHITE used on the first batch of boards.
Start by fitting the 16 and 24 Pin IC sockets. The sockets are all aligned in the same direction and the notch in one end of the IC socket aligns with the notch in the silkscreen overlay. The notch will be to the left as per the board orientation shown.
Figure 5 - Identifying Pin 1
provides further details of the IC sockets recommend for the controller. If you decide not to use sockets (bad idea if you ask me) Pin 1 of the IC aligns to the square solder pad on the PCB.
Figure 5 - Identifying Pin 1
Fit the four 0.1uF capacitors next. The capacitors have no polarity, so you can install them onto the board in either direction. The capacitors are located to the front of the four IC sockets as shown on the PCB overlay.
You will see there are three resistors located on the PCB, below each of the LED controller ICs. They are labelled R1, R2, and R3. Note that the resistor is a 1k value (typical band markings are brown black red gold)
Fit the power LED and resistor to the board. The LED must be orientated to the board as per the overlay. The notch of the LED aligns to the flat on the overlay (K). You will also see a square solder pad for the LED, and this is for the shorter leg of the LED (K). Note that the resistor is a 407R value (typical band markings are yellow violet brown gold)
Next fit the power connector to J1 (Molex SL connector Vertical Header 2 Pin). The square pad on J1 signifies the + 5VDC connection. You also need to fit the DIL header. This is a 4 x 2 0.1 pitch DIL header. The shunt should be placed on SEL 1 for the first board. The last construction task is to fit all ten RJ45 sockets to the board. Some manufacturers RJ45 sockets are a bit tighter to fit onto the board; just take your time and align the pins first before you gently seat the lock lugs through the boards.
At this point you will have now completed the installation of all of the parts to the controller. Before you go ahead and insert the 74HCT4514 and MBI5027-GNs into their sockets, I would suggest you visually inspect the board and check to make sure there are no solder bridges between the solder pads, and that the solder joints are all a good quality. I would also recommend cleaning the copper side (bottom) of the PCB with a quality board cleaner to remove and resin residue after soldering.
Now fit the ICs into the sockets, noting that the notches on the ICs will be facing the IN and OUT RJ45 sockets.