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Flexible, attractive There’s nothing particularly new about moving message displays – except this one. Not only is it easy to build, it's easy to program, it looks good. . . and the price is right. Design by Atilla Aknar* Article by Ross Tester A great deal of time and effort has gone into the design of this moving message display. And the end result is a very attractive proposition – in all senses of the word. For a start, the kit price is significantly less than any commercial product which could be classed as equivalent. That’s a welcome change – we all know that these days building a kit can often cost as much as buying a finished product (or even more). Second, the display looks good. It’s housed in a clear acrylic tube with a red acrylic filter and black backing and end caps. This method means the display is suitable for placing on a shelf or desk, hanging from a wall or even hanging from a ceiling (see inset box). Third, it is flexible. We have shown a “double” display – that is, two PC boards linked together to form an 8-unit display. However, there’s nothing to stop you making a mini version with only one PC board and a 4-unit display. Finally (and perhaps most importantly), the system is incredibly easy to use. No special PC software is required – just a “dumb terminal” capable of sending and receiving via the RS232 (serial) output. Almost certainly your computer already has just such software built in; in some cases (eg, Windows 2000 users) you may need to download some freeware from the ’net. Basically, all you have to do is type your text into the PC, it sends the text on through the RS232 port to the message board’s EEPROM message store and the text stays in memory until another message is written, even if power is cut. A somewhat similar Moving Message Display was published in the February 1997 issue of SILICON CHIP. However, when we say “somewhat similar” any comparison between that project and this is just about limited to the name! The major difference is that the earlier project was totally controlled by a PC and had to remain connected to it. This one is fully self-contained: once the message is programmed in via the computer, the display runs independently. The other big difference is in the number and type of LEDs: the earlier one used 336 individual LEDs in a 48x7 matrix. This one uses eight integrated LED displays, each with a 5 x 7 matrix, making 280 LEDs in total. This is what your Moving Message Dispay should look like before it is placed in its tube “case”. Of course, there’s nothing to stop you using it just like this if you want to but the red Acrylic filter in front makes it look much better. 18  Silicon Chip So instead of 672 soldered LED joints you make just 112 (28 per display). The circuit The circuit, shown in Fig.1 (overleaf), is reasonably standard for this type of equipment. Most of the clever work is done inside the PIC micro-controller! Power is provided by a nominal 12V DC plugpack capable of supplying about 350mA. This is regulated to about 5.6V by a 7805 5V regulator with a silicon diode between its “ground” input and the circuit ground. This diode effectively lifts the normal 5V output of the regulator by the voltage drop across the junction, around 0.5-0.7V. A MAX202CPE communications chip (IC3) accepts data from the serial port of the computer in a 9600,8,N,1 format (ie 9600 baud, 8 data bits, no parity bits, 1 stop bit). This is fed into the TX and RX inputs of IC1, a PIC16C63A. PIC Ports RA0-RA3 connect to the message store IC, a 93LC46B EEPROM, (IC2) which can store up to 125 characters. This is non-volatile memory, meaning the contents of the ROM are not lost when power is removed. The contents will in fact stay in memory for many, many years (around 40 years guaranteed) which makes the message board ideal for very occasional warning messages. The OSC inputs are connected to a 3.58MHz crystal oscillator circuit which provides timing for the entire circuit. This particular frequency crystal is used because they’re made in the hundreds of millions for NTSC TV sets – so they’re really cheap! The microcontroller’s output ports, RB0-RB7, RA4, RA5, RA2 (which does double duty) and RC0-RC4 are all used in the multiplexing and driving circuitry for the 7 x 5 matrix of LEDs, each housed in a single TC20-11SWRA display (DISP1-4). Interposed between the LEDs and PIC are three ULN2003AN high current buffers (IC5, 6 and 7) connected to the LED columns, along with LED row driver transistors Q4-Q10. As there are eight of the LED displays each with five columns, there are 40 columns to drive. The PIC allocates 40-byte buffers corresponding to the message and proceeds to drive column 1 with the first part of the first letter of that message. For example, if the message begins with the letter B, D, E, F, H, K, L, M, N, P or R, the whole first column of LEDs (on the right) is lit. This is then moved to column 2, then column 3, and so on. In the meantime the PIC has told And here it is inside the case, complete with filter. The cable in front is all that is required to program it from virtually any PC running a terminal program. JULY 2000  19 20  Silicon Chip JULY 2000  21 Note the groove down the middle of the boards: if the “mini” version is constructed, the boards snap apart along this line. For the “maxi” version, the two boards require seven inter-connecting links as shown here and in the illustration below. column 2 to light in the pattern corresponding to the next part of the first letter: for example, if it were a B, D or E the top and bottom LEDs in the column would be lit. When column 2 empties into column 3, the contents of column 1 are moved to column 2 and column 1 lights with the next portion of the letter. This process happens continuously and the eyes, with their persistence of vision, are fooled into believing that they are seeing a full word, indeed a full message, whereas at any particular instant in time, all that would be seen is a series of LEDs. To prove the point that it is indeed an optical illusion, try getting so close to a moving message display that you can no longer read words. Or fix your gaze on either the start or the end of the message. All you will see is a mess of flashing LEDs! Mini or full version? What we have been describing so far is only half the circuit. We mentioned before that it could be built in a “mini” version using only half the LEDs. The full version consists of two nearly identical PC boards, the second board missing a few components and with a few links across the back of the boards. Note that the PIC chip is programmed slightly differently in the second board so don’t mix the PICs up when constructing. It won’t work! Data output is taken from the RC3, RC4, RC2, RC1 and RC0 ports of one Components are mounted on both sides of the PC board. Most are on the “bottom” side (Fig.2 above – note only one board shown) but the LED displays mount on the top side (Fig.3 below), along with the seven links between the Part 1 and Part 2 boards. 22  Silicon Chip The completed “maxi” version of the moving message display with two near-identical PC boards connected together to form an eight-letter display. We say “near identical” because there are differences – not the least being the PIC chips themselves which are are certainly not interchangeable. Each contains different code. PIC and fed into the RC7, RC6, RA3, RA2, RA1 and RA0 inputs of the second PIC. On the second board, the MAX202 RS232 communications chip (IC3), the 93LC46 EEPROM message store (IC2) and associated capacitors (C7 to C11) are not used. The housing Apart from the fact that it works so well, one of this project’s biggest assets is that it looks great! The entire project (with the obvious exception of the RS232 lead) is housed in a 305mm length of 65mm (OD) clear acrylic tube with black end caps glued in place. A 300 x 53mm length of 3mm red acrylic is used as a filter in front of the LED displays, effectively hiding all but the lit LEDs. The LED displays mount on one side of the PC board(s) while all components mount on the other. A 305 x 110mm piece of dark window-tinting film wraps around the rear of the acrylic tube, hiding everything inside except the LED displays. – how long you want the cable to be!). Connections We will assume you are making the “maxi” version (ie, eight LED displays) because that’s the way the kit is supplied (including the case length). If you only want the “mini” version (four LED displays), the two PC boards will need to be snapped apart at the V-groove between them. You’ll also need to cut the acrylic tube to the right length (and that’s not an easy task!). Before we start on the electronics side we’re going to work on the “case”, which consists of an acrylic tube, a red acrylic filter, two end caps and a sheet of dark window-tinting film. The reason for this cart-before-thehorse approach is that the filter must be glued inside the tube and the film fixed to the outside of the tube. The latter takes several hours to dry, so while that’s happening you can get on with the electronics. First, though, there are two holes needed for the DC power socket and the 3.5mm stereo socket (serial data) in one end of the tube. Exact position isn’t important – as a guide ours were 25mm and 45mm from one end. We rebated the hole for the 3.5mm socket so the nut would be recessed. Secure the length of red acrylic inside the tube, opposite the drilled holes, with a drop of acrylic glue (available at hobby shops) on each corner (super glue shouldn’t be used because it leaves a white residue on the acrylic). The sheet of window tinting film should be just the right length to wrap around the outside back of the tube from one edge of the red acrylic filter to the other. A standard 2.1mm DC socket is mounted through the rear of the tube to allow connection to power. That part was easy. The harder part was mounting a standard 9-pin “D” serial connector on the curved surface. In the end Atilla came up with an elegant solution: drop the D connector and use a 3.5mm stereo audio socket instead! Only three connections are required from the computer’s serial port so a 3.5mm stereo jack plug and socket was ideal. And it allows a very neat connection – the only slight hiccup is that you’ll need to make up your own serial cable because, as far as we know, no-one has ever made or used a 9-pin D to 3.5mm stereo cable or adaptor before now. Fortunately, that part is really easy (and you can choose – within reason Construction JULY 2000  23 (Left): It's a good idea to solder only two LED displays in place to test it – if these two work, the odds are that it will all work. If they don't work, you only have two displays to unsolder! Dunk the tube in water containing a small amount of mild detergent. Peel off the protective backing sheet from the film and carefully dunk that as well (the detergent makes the water wetter!) Remove both and shake off excess water, then place one end of film on the outside of the tube, adhesive side in, right along the line of the red acrylic filter inside the tube. Slowly wrap the film right around back of the tube, removing any air bubbles as you go with a cloth used as a squeegee. When you get to the other end of the film it should be a perfect line-up with the other side of the red acrylic filter inside. The detergent water means you have a bit of “slip” available if you need to The acrylic filter is marginally narrower than the PC board (though exactly the same length). This is to account for the curvature of the tube: the PC board mounts right in the middle but the filter sits closer to the side. move the film; indeed, it will allow you to remove it completely and start again if necessary. When satisfied that you have a perfectly placed film, put the tube aside to dry for several hours (overnight is ideal if the tube is left in a reasonably warm [not hot] place). Now, back to the electronics assembly. First check the PC board for obvious defects (remember it is double sided). Most components, with the exception of some wire links and the LED displays, mount on one side of the board. You can easily identify which side the links and displays mount on by the words “DISP4” through “DISP1” printed on it. Proceed as you would with any project assembly: mount all the low profile, non-active components (resistors, crystal and capacitors, taking due care with electrolytic capacitor polarity) followed by the smaller active components (diodes and transistors). Note that the main filter capacitor (C14) needs to be pretty small, otherwise the assembled board may not fit properly in the tube (it may foul the power or serial sockets). The kit will have small capacitors but if you source your own they may need to be mounted about 10mm above the board and then bent over at right angles, lying on top of D1, C12, etc. All ICs except the PIC are soldered directly into the board; again, check the polarity! Solder the PIC’s socket in Parts List – for “mini” version* 1 x PC board coded M4399 (two boards attached together) 1 x clear acrylic tube, 305mm long, 57.5mm ID, 63.5mm OD (case) 1 x red acrylic sheet, 305mm long, 50mm wide, 3mm thick (filter) 2 x black end caps to suit tube (glue on type) 1 x 305mm x 110mm sheet self adhesive dark window tint film 1 x 3.5mm stereo phone socket 1 x 2.1mm DC socket 1 x 10-way PCB header plug Semiconductors 1x 1N4001 silicon diode 1 x Pre-Programmed PIC16C63A (IC1)# 1 x 93LC468 (IC2) 1 x MAX202 RS-23 communication chip (IC3) 1 x 7805 regulator (REG1/IC4) 3 x ULN2003A high current drivers (IC5,6,7) 4 x TC20-11SRWA 7x5 LED displays (DISP1-4) 7 x BC327 PNP transistors 3 x BC337 NPN transistors 24  Silicon Chip Capacitors 1x 470µF 25VW PC mounting electrolytic(C14) 1x 100µF 16VW PC mounting electrolytic (C15) 8 x 0.1µF polyester (C3, C7-C13) 2 x 39pF ceramic (C1, C2) Message Board Programming 1 length (as required) 3-conductor (or twin shielded) cable 1 x 3.5mm stereo phone plug 1 x 9-pin D plug (to suit computer serial port) Suitable PC terminal program ** Resistors (1%, 0.1W) 15 x 4.7kΩ (R1-R8, R12-R18) 3 x 1kΩ (R10,R19,R20) 8 x 22Ω (R21-R27) NOTES: * All of above semiconductor, resistor, capacitor and crystal lists must be doubled for maxi version, with exception of IC2, IC3, C7, C8, C10 & C11 – only one of each required. The tube, filter and tint film specifed are for the “maxi” version. Crystal 1 3.579545MHz Miscellaneous 7 lengths approx 150mm long very thin insulated hookup wire (for links in maxi version) 5 lengths approx 50mm long thin insulated hookup wire (for PC board to two sockets connections) 1 x plugpack supply, 12V DC <at> 500mA output Acrylic glue Foam plastic, bubble wrap, etc for packing #IC1 requires different code for each half of display. R11, C4-C6 are not included in either version nor is any position shown on PC board **Term90 software may be downloaded free of charge from www.siliconchip.com.au How the display fits in the tube: this photo and drawing should reveal all! The one thing we haven’t shown is how to put the window tinting film on the outside of the tube but this is fully explained in the text. The packing material behind the PC board stops any movement – it can be just about anything nonconductive. Foam rubber/plastic is ideal. PC BOARD LED DISPLAYS 58mm (ID) CLEAR ACRYLIC TUBE (notch to top) but don’t fit the PIC yet. You can also solder in the regulator; it lies flat down on the PC board with its legs bent down at 90°. Before commencing work on the opposite side of the board, check your soldering carefully. Remember most of your soldering will be covered by the displays so if you’ve made a dry or suspect solder joint or a bridge, now’s the time to discover it! We suggest you use a magnifying glass to inspect the whole of the boards thoroughly. PACKING MATERIAL POWER AND PROGRAMMING SOCKETS RED ACRYLIC FILTER the inside with nuts on the outside. If your sockets are the type which mount from the outside with the nut on the inside, you’ll need to unsolder the wires before final assembly. At this stage you don't need to connect the serial input but you can solder the wires on now if you wish. It’s best to use a black wire for the ground connection; please yourself which other colours you use. Now solder in just two of the LED Links The full or “maxi” version requires seven long links between the two (joined) boards using fine insulated hookup wire. Five are for data, two for power. Place these links on the LED display (ie opposite) side of the boards where shown before continuing. Testing If you’re satisfied with your workmanship, it’s time to put it to the test. The reason we do this now, before completion, is that it is very much harder later on, once all eight LED displays are in place and even harder once the message board is mounted inside its case. First, solder two wires (red and black are good choices) to the “PWR” inputs – 50mm is ample. Solder these to the DC socket, matching the polarity of the plugpack. Usually, plus (red) is the centre pin but don’t bank on it. If in doubt, check it with a multimeter first. By the way, it is preferable to use sockets which mount through from COMPONENTS The DC power socket (left) and the 3.5mm stereo “programming” socket (right). With 20/20 hindsight, we would have swapped these around... displays into each half of the board – say one in DISP1 position on the right board and one in DISP 4 position on the left board. Note that the soldering is (obviously!) done on the component side of the PC board. You may note that they can go in either way – but one way won’t work! The type number and other writing along one edge of the display is the bottom of the device. When you hold the PC board so that you can read the writing on it (eg, DISP4, DISP3 etc), the display is DARK WINDOW TINT inserted so that the writing on it goes to the bottom. Finally, insert the PICs into their sockets – again, check the polarity. It would be a real shame to see the most expensive component go up in a puff of smoke with that awful, acrid smell! Now connect the plugpack to the DC input socket and apply power. If all is well, you should see first of all the righthand display LEDs flashing and then shortly after the lefthand display LEDs should do likewise. You probably won’t be able to make out any meaningful message – just the LEDs flashing is a good sign. If the LEDs don’t flash, you’ll need to go hunting for the reason. It’s almost certain to be an incorrectly placed component or a bad solder joint. With components on both sides of the board, it’s difficult to remove anything to trouble-shoot. That’s why we suggested you examine the board with a magnifying glass before soldering in the displays. You could check that you get about 5.6V between the output of the 7805 and the negative supply. If you have an oscilloscope you could also check that the crystal is oscillating. Apart from that, the only other easy check to make is that the PIC microcontroller is not only inserted correctly but also that all its pins are actually in their respective holes (it’s easy to bend a pin out of position). Finishing off If you did get flashing LEDs, you can now insert and solder the rest of JULY 2000  25 Programming it: as easy as 2-1-3! We mentioned before that programming the Moving Message Display is one of its best features: it’s easy! You can use just about any dumb terminal program and communicate with the Message Board in 9600,8,N,1 format. Because we use Windows 2000 (which doesn’t include a suitable terminal program) we used a freeware program called Term90 which can operate in a DOS box under Windows anything. The following is a guide to using this program which can be downloaded free of charge from the SILICON CHIP website, www.siliconchip.com.au Install the software as normal under Windows 95, 98, NT or 2000. SETTING UP THE SIGN PROGRAMMING 1. Plug the data cable into serial port COM2 on your PC. The Menu displayed is as follows. To setup your message on the Moving Message Display, use the following commands: 2. Plug the stereo jack into the back of the Moving Message Display. 3. Plug the power connector into the back of the Moving Message Display and the power pack into the power point. DO NOT turn on the power at this stage. 4. Start the TERM90 terminal program. When it starts you will see a blank screen with some menus. DO NOT change any of these menus. 5. Now turn on the power to your Moving Message Display. The display should read “MINI DISPLAY” and you should see a MENU displayed on your computer screen.    You are now ready to start programming your message.    1.   2.   3.    4.    5.    6. Type new message Delete existing message Program message Message scroll speed = FAST Message scroll speed = MEDIUM Message scroll speed = SLOW The CAPS LOCK key must be pressed to enable your text to be sent to the Moving Message Display 1. Press 2 to delete any existing message. 2. Press 1 and a sub menu will be displayed to enable you to type your message – in normal, BOLD or REVERSE text if required.    Press CTRL+B to display the text following in BOLD (this will display a smiley face symbol). CTRL+R REVERSES the text following (this will display an up & down arrow symbol). Note – reversed text is much harder to read. CTRL+E ends the text enhancements. 3. Adjust the scroll speed by selecting option 4, 5 or 6 from the main menu. Type in your text and you will see this displayed in real time on the Moving Message Display. 4. DO NOT use the arrow keys to cursor up, down, left or right. This will corrupt the displayed text and you will have to start again. Use the backspace key to move over the text you want to change and retype your text. 5. After your message is complete press ESC; you will see a prompt MESSAGE ACCEPTED. Now press 3 to program the Moving Message Display. You will see a prompt MESSAGE PROGRAMMED. Press ESC to clear the screen and re-display the main menu. 6. If you want to change your message simply follow the steps under SETTING UP THE SIGN and then press 2 to delete your message and then follow the steps under Programming. 7. Finally select FILE, EXIT and OK to close the terminal program, unplug your data cable and place the Moving Message Display in the appropriate location. The TERM90 screen, run either under DOS or in a Windows DOS box. It’s as simple as 2-1-3: The top part of the screen comes on when you turn on the Moving Message Display. Pressing 2 deletes any existing message, pressing 1 readies the terminal for your new message. Pressing 3 programs the new message into the unit, where it will stay until deleted. 26  Silicon Chip A really nifty method of mounting . . . Just imagine the visual impact of this Moving Message Display apparently floating in space with no visible signs of support and or power wires… We’ve seen this done before by professional display companies – all it takes is two lengths of some very fine, black insulated wire (such as one of the four conductors from telephone cable). The wires not only support the unit, they provide the power connections. The idea is to wrap the wires tightly around the unit right the LED displays. It’s probably a good idea to carefully remove the PICs and store them back in their anti-static packaging before soldering. As you place each display, make sure the labels all go the same way – down! If you didn’t do it before, solder in the three serial input wires and connect them to their socket. Fig.2 shows the wiring for both the sockets. up close to the end caps, with the power connections made by running the wires along the back of the unit, following the edge of the tint film. You could even dispense with the DC socket and wire directly to the PC board. Done right, the wires are almost invisible. The opposite ends are secured to what ever you want to hang it from. The one thing to watch is that as both wires are black, you have to be careful with polarity. The result looks fantastic – especially if the room is just a little dark and the wires cannot easily be spotted. tube: it should be a reasonably snug, but not too tight, fit. Slide it all out again, taking care not to scratch the acrylic. You will need to cut or pierce the tinting film with a very sharp knife or scalpel to give access to the two holes you drilled before. Be careful – it’s easy to damage the film. Now slide the assembled PC 3.5mm STEREO PLIUG 5 1 5 2 3 6 DB-9 FEMALE CONNECTOR (SOLDER SIDE) 9 Finally, carefully re-insert the PIC chips and the electronics side is complete. Now when you connect power you should see the complete message which is programmed into the new PIC chip: “MINI DISPLAY”. If you get this message, it’s a fair bet that your unit is working properly and ready to program. You might like to skip to the “programming” section and type in a message just to make sure! You may have noticed that there are quite a number of apparently empty holes on the finished board. These are not component holes as such, but “vias” or plated-throughholes which connect the tracks together where required on opposite sides of the board. Providing you have components wherever shown on the component overlay (fig.2), you’re ready to get your display up and running. Final Assembly First step is to make sure it all fits! Slide the whole shebang into the inside and fit the appropriate nuts. We mentioned before that some DC power sockets mount from the outside with the nut on the inside. If yours is one of these (as will be supplied in the kit), you will need to unsolder the wires, mount the socket and then very carefully resolder, taking care not to get the iron too close to the acrylic. It melts! RING BODY TIP Here's how to make up the programming cable to operate from the serial port on your PC. The length can be as long as you like (within reason!). This cable is shown in the photo on page 19. board(s) into the tube, wires and connectors end first, about three quarters into the tube. The assembly goes on the side of the red acrylic closest to the drilled holes. Before sliding all the way in, push the two sockets (3.5mm and DC power) through their holes from the Where do you get it? The Moving Message Display was designed by 4D Systems Pty Ltd, who hold copyright on the design and on the program residing in the PICs. A complete kit of parts is available from 4D Systems for $189 (including GST) plus pack and post. Contact 4D Systems at Suite 2, 3-5 Station Road, Auburn NSW 2144. Phone (02) 9649 5065; fax (02) 9649 4324 Email: sales<at>4dsystems.com. au Web Site: www.4dsystems. com.au * Atilla Aknar is Managing Director of 4D Systems Pty Ltd. (While we mounted our 3.5mm socket closest to the outside edge of the tube, it may be better to swap the two sockets around and mount the DC socket closest to the edge to make soldering easier). The assembled PC board is a reasonably good fit inside the case but it was able to move. We didn’t want this, so we pushed some scraps of foam rubber in behind the board (ie, component side) to stop it rattling. You might need to do similar. Before gluing on the two end caps, connect power and check that everything still works. If so, a couple of dobs of acrylic glue on the end caps will secure them in place. And that’s just about all there is to it. By now, you’re starting to agree with us that the Moving Message Display is the equal of any commercial unit – and you’ve saved money building it. Now, what are you going to tell the world about with your new Moving Message Display? SC JULY 2000  27