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Pt.2: By MAURO GRASSI Multi-Purpose Car Scrolling Display Construction & software installation In this month’s article, we guide you through the construction of the Car Scrolling Display. We also show you how to install the software driver that’s used to communicate with the display via a USB port on a Windows PC. A LL THE PARTS for the Car Scrolling Display are installed on two PC boards – a main board coded 05101091 (134 x 86mm) and a display board coded 05101092 (124 x 75mm). These two boards are stacked together with a red Perspex window and are secured using Nylon spacers, 62  Silicon Chip washers and screws. Note that there is no wiring between the two boards. The display board simply plugs into the main board via connector CON6. Note also that the display board is smaller than the main board. That’s been done so that when the two boards are stacked together, the screw terminal blocks on the main board are exposed for easy access. Main board assembly Fig.6 shows the assembly details for the main board. Begin by checking the board for cracks in the tracks or any shorts between adjacent tracks. This is easier to do before installing the parts and can save you trouble later. Once you are convinced that the PC board is OK, start the assembly by soldering in the 10 wire links. You must do this first, as two of these links (LK5 & LK6) are underneath the 40-pin IC socket. These links should be installed siliconchip.com.au 3 2 1 2 3 6 1 5 4 2 3 1 1 F + 33k 4004 10k 10k 4004 33k Q18 + ZD1 4004 16V REG1 LM2940 100nF LK4 LK2 470 F D6 100nF 100nF 47 F D1 10k 10k 10k 1k 1k D5 1k Q19 22pF 10nF 1k 10k 10k 1k 10nF 100nF 1 F LK3 LK8 LK5 LK6 X1 22pF 1 8002/90 GM DRAOB NIAM .PSID RAC 10 11 12 13 14 15 17 LK9 18 19 20 21 22 23 24 25 26 27 1 2 3 4 5 6 7 8 9 D4 100nF Q16 10  1W 8002 PIHC NOCILIS 19010150 CON5 100nF LK1 220 F + D2 10k IC1 PIC18F4550 D3 22k 22k 22k 22k LK10 10k 56k 4004 Q17 2 D7 4148 100nF + CON4 4 1 2 3 4 5 6 LK7 1 3 CON3 16 1.5k 10k CON2 5819 CON1 CON6 + 4 4004 Fig.6: follow this parts layout diagram to build the main PC board. Take care to ensure that all polarised parts go in correctly and don’t install the PIC microcontroller in its socket until after the power supply has been checked – see text. This view shows the fully assembled main board. Note that the five electrolytic capacitors are all mounted with their bodies parallel to the board surface. using tinned copper wire. You can straighten this link wire by first clamping one end in a vise and then pulling on the other end with pliers to stretch the wire slightly. After that, it’s simply a matter of cutting the links to length and using pliers to bend their leads down at right angles so that they fit the PC board. There are 24 resistors on the main PC board and they can be soldered in next. You must make sure that the siliconchip.com.au correct value is used at each location. The colour code table shows how to decipher the values but it is also prudent to check each one with a multimeter before it is soldered in place. Note that the 10Ω resistor must be rated at 1W. Once the resistors are in, the diodes can be installed. There are eight diodes in total, of four different types. Begin by installing 16V zener diode ZD1. Refer to the component overlay for its location and orientation! Remember that the cathode of a diode is normally indicated by a stripe. The signal diode (D7, a 1N4148) is used for ICSP (In Circuit Serial Programming) and is installed near CON6 (the ICSP header). You only really need it if you intend to program the microcontroller (IC1) in circuit, otherwise it can be left out. Diodes D5 & D6 are next on the list. Note that these were shown as 1N5819 January 2009  63 Q15 680 Q13 680 680 Q12 Q10 1 680 YALPSID RAC 680 Q8 Q7 TA12-11EWA LK16 1 680 680 Q5 Q3 29010150 USB TYPE B TA12-11EWA LK10 680 680 LK2 + 470 F LDR LK17 LK7 TA12-11EWA 1 2 1 3 4 11 12 13 14 15 SOCKET (VERT) 21 22 23 24 25 26 27 1k 680 TO S1 LK14 1k LK21 1 2 /90 3 8002 4 5 GM 6 7 82k LED ARRAY 3 LK13 LK8 LK19 680 680 680 680 3.3 680 LED ARRAY 2 LK9 LK15 Q14 Q9 Q6 Q4 Q1 LK4 LK3 LK18 LED ARRAY 1 LK5 LK6 LK1 IC3 ULN2003 LK12 LK11 Q2 IC2 74HC595 100nF Q11 LK20 16 17 18 19 20 CS Fig.7: here’s how to install the parts on the display board. This is the completed display board. Make sure that the LED arrays are correctly oriented. Schottky types on the circuit diagram (Fig.3) last month but in practice, 1N4004 diodes will do and that’s what are now specified in the parts list. Be sure to install them with the correct orientation. By contrast, diode D4 must be a 1N5819 Schottky type (as originally specified). This can now be installed, followed by the five remaining diodes which are all 1N4004s. The four transistors can now all go in. These are all BC337 NPN types and each must be correctly oriented, as shown in Fig.6. Now for the capacitors. The ceramic and the 100nF monolithic capacitors 64  Silicon Chip are not polarised and can go in either way around. However, the electrolytic capacitors are polarised, so be sure to install them as indicated on the overlay. Note particularly that all the electrolytic capacitors must have their leads bent by 90° so that their bodies lie horizontally on the PC board – see photo. Do not mount them vertically; if you do, they will later interfere with the bottom of the display board when the boards are stacked together. Once you’ve installed the capacitors, you are ready to install the connectors and the IC socket. Install the 40-pin IC socket first, making sure Above right: the completed display board with two of the LED arrays removed to show their 7-pin socket strips. that it is oriented correctly with its notched end as indicated. Note that the IC is not installed in the socket just yet. That step comes later, after some preliminary checks of the supply rail. Install the right-angled 6-pin ICSP header (CON5) only if you intend to program the microcontroller. Note that you will need to cut away the plastic locating guide on this connector if you intend to use the PicKit2 programmer from Microchip. In addition, CON5 should be mounted about 2mm above the PC board in order to fit the PicKit2 programmer. The rest of the connectors are screw terminal blocks CON1-CON4. These consist of 2-terminal and 3-terminal blocks which are combined by sliding their dovetailed ends together. As shown, CON1 & CON4 are each made by sliding two 2-terminal connectors together, while CON3 consists of two 3-terminal connectors. CON2 is a single 3-terminal connector. Making up CON6 CON6, a 27-way connector, is made by first cutting a 40-pin IC socket into two 20-pin sockets. You can use a small fine-toothed hacksaw to do this job. As shown on Fig.6, CON6 is split into three parts. The first is a 14-pin connector, the second is a 5-pin connector and the last is a 7-pin connecsiliconchip.com.au Follow this photo in conjunction with Fig.7 when installing the parts on the display board. Note that pin 1 of each LED array goes to lower left. tor (note: pin 15 is not used). You make these by first cutting one 20pin connector into 14-pin and 5-pin connectors. The 7-pin connector is then cut from the remaining 20-pin connector. Regulator REG1 can go in next. As shown, this device is mounted horizontally with its leads bent down by 90°, to go through their matching PC board holes. In addition, the regulator must be fitted with a small U-shaped heatsink and this is sandwiched between the regulator’s tab and the PC board. Secure this assembly to the PC board using an M3 x 10mm screw, lockwasher and nut before soldering the regulator’s leads. If you solder the leads first, the soldered joints may crack as the mounting screw is tightened down. Note that we specified an LM2940CT-5 low drop-out regulator in the schematic (Fig.3) published last month. However, you can also use a common (and much cheaper) 7805 regulator in its place, if you wish. The only drawback here is that using the 7805 means that you will have to power the circuit from a 12V supply. By contrast, the LM2940CT-5 will work with supply voltages down to as low as 9V. The LM2940CT-5 also contains inbuilt reverse polarity protection but we don’t use it in this circuit. That’s because reverse polarity protection is provided by diode D1. Construction of the main PC board can now be completed by installing the 20MHz crystal. It’s non-polarised and so can go in either way around. Display board assembly Fig.7 shows the parts layout on the display board. Begin the assembly by installing the 21 wire links (LK1LK21). Some of these links are quite long and run close together, so it’s important that they be straight before they are installed (stretch the link wire to straighten it). The resistors can go in next. Note that the 3.3Ω resistor must be rated at 0.5W, while the others are all rated at 0.25W. Now solder in the two 16-pin IC sockets. These must be oriented with their notched ends as shown on Fig.7. Table 1: Resistor Colour Codes o o o o o o o o o o o siliconchip.com.au No. 1 1 4 2 10 6 15 2 1 1 Value 82kΩ 56kΩ 22kΩ 33kΩ 10kΩ 1.5kΩ 680Ω 330Ω 10Ω 3.3Ω 4-Band Code (1%) grey red orange brown green blue orange brown red red orange brown orange orange orange brown brown black orange brown brown green red brown blue grey brown brown orange orange brown brown brown black black brown orange orange gold brown 5-Band Code (1%) grey red black red brown green blue black red brown red red black red brown orange orange black red brown brown black black red brown brown green black brown brown blue grey black black brown orange orange black black brown brown black black gold brown orange orange black silver brown January 2009  65 A 113.25 A HOLES A: 3.0mm DIAMETER 25 23.5 13mm DIAMETER HOLE FOR PUSH BUTTON SWITCH 75 Preparing the front panel 64.8 17 13 x 13mm CUTOUT FOR USB SOCKET MATERIAL: 3mm THICK RED PERSPEX SHEET 21 113.25 A A 124 Fig.8: follow this drilling and cutting diagram to make the front panel. It’s made from 3mm-thick red Perspex measuring 124 x 75mm. Note that although these sockets are optional, we do recommend them. They make it much easier to replace the ICs, if necessary. The next step is to install six 7-pin socket strips to accept the dot-matrix LED arrays. These are made by cutting three 14-pin IC sockets in half and then cleaning up the edges using a small file. That done, the sockets strips can be soldered in place. These sockets are used simply to space the LED arrays off the board, so that they later sit close to the red Perspex front panel. They also make it easier to replace a module in the unlikely event that it fails. You can now install the two ICs in their sockets, making sure they are correctly oriented. Don’t get these two ICs mixed up – IC2 is the 74HC595 shift register, while IC3 is the ULN2003 Darlington array. The three LED modules can also be installed in their sockets, each with pin 1 at bottom left. Pin 1 of each module is indicated by a digit on the side. Once this is done, you can solder in the 15 BC327 transistors. Be sure to orient them as shown and push them down onto the board as far as they will comfortably go before soldering their leads. Next, solder the two capacitors in place. The 100nF monolithic type is not polarised but the 470μF electrolytic is so take care when installing it. The three pin connector strips that make up CON7 can now be installed. These are made from a 32-way strip that’s cut into three pieces of 14, 7 & 5 pins. As shown in the photo, these are installed from the component side of the PC board. Now install the USB type B socket. It sits vertically on the PC board and only fits one way around. Its two tabs can be bent flat against the underside of the board to secure it in position before soldering. Solder its four pins and both tabs to the PC board. M3 x 25mm NYLON SCREWS M3 NYLON SPACER 12mm LONG M3 NYLON FLAT WASHERS (RED PERSPEX FRONT PANEL) M3 NYLON SPACER 12mm LONG (DISPLAY BOARD) M3 NYLON FLAT WASHERS M3 NYLON SPACER 12mm LONG (MAIN BOARD) The last thing to do is to solder in the LDR. This should be installed about 10mm above the PC board, so that it later sits just below the front panel. That completes the assembly of the two PC boards. The next step is to make the front panel. M3 NYLON SPACER 12mm LONG The front panel is made from a single piece of red Perspex measuring 124 x 75mm (ie, the same dimensions as the display board). Fig.8 shows the cutting and drilling details. There are four 3mm-diameter holes for securing it to the display board plus a larger (13mm) hole for pushbutton switch S1. In addition, you need to make a square cut-out to provide access to the USB socket. Once you’ve cut and drilled the panel, fit the pushbutton switch in place and wire it back to the display board using two 60mm lengths of hook-up wire. The front panel is then fitted with four M3 x 12mm tapped Nylon spacers plus four Nylon washers which are secured using M3 x 25mm Nylon screws – see Fig.9. The display board can now be fitted in position over the Nylon screws. Another four Nylon washers are then fitted, after which another four M3 x 12mm Nylon spacers are wound on. Preliminary tests Before attaching the main board, it’s a good idea to carry out a power supply check, to confirm that the +5V supply rail is correct. Note that this should be done with microcontroller IC1 out of its socket. First, connect a 12V battery to the power input terminals of CON1 (pin 4 is the +12V input, pins 2 & 3 are ground). Apply power and check the voltage at pin 1 of CON3. If it’s close to +5V, then everything is in order. Note that this voltage can normally range from 4.9-5.1V. A voltage above Fig.9: the two PC boards and the front panel are secured together using M3 x 12mm tapped Nylon spacers, M3 Nylon washers and M3 Nylon screws. M3 x 6mm NYLON SCREWS 66  Silicon Chip siliconchip.com.au The display board/front panel assembly plugs into the main board and is secured using four M3 x 6mm Nylon screws. Take care to ensure that the regulator heatsink clears the underside of the display board. 6V or lower than 4.5V indicates that there is a problem and you should disconnect power immediately. Assuming that the +5V rail measures OK, you can now disconnect power and install IC1 in its socket. Note that this IC must be programmed with the firmware hex file. If you are building this project from a kit, it will be supplied preprogrammed. Final assembly Having checked that the +5V rail is OK, it’s time to complete the assembly. This simply involves plugging the display board into the main board and then securing the assembly using four M3 x 6mm Nylon screws. Switch on Once the assembly has been comsiliconchip.com.au The Software Features In Brief In next month’s article, we explain the software features in detail. In the meantime, here’s a quick summary. First, the software calibration allows you to read almost any sensor with a varying voltage, resistance, frequency or duty cycle output. Calibration involves entering a few calibration points. The software then computes a polynomial which passes through these points and that’s stored in non-volatile memory. You can therefore use this project as a “speedo corrector”, by calibrating the variable to read the correct speed (note: car speedos often intentionally read high). You can measure the output of a resistance-based sensor directly (without a voltage divider). We’ve held the calibration instructions over to next month’s article, as they were too long to include here! Once calibrated, you can name the variables and enter the units, as well as minimum and maximum values. You can choose which to display and in what order, as well as the number of digits after the decimal point. You can select optional averaging on each variable and the speed of scrolling and the brightness of the display. Each of the six variables has an accumulator (for running totals) as well as delta values (showing the difference in the readings). There are also two programmable outputs (for a relay or buzzer) that can switch on limit conditions. You can do real-time data logging of the variables via the USB port (with selectable sampling frequency) and the data can be exported to a spreadsheet to create graphs. Other features include protection for the battery supplying power (if used in a car) and fine tuning options for greater accuracy! All will be explained, next month. January 2009  67 Parts List Main Board 1 PC board, code 05101091, 134 x 86mm 2 40-pin IC sockets 4 2-way screw terminal blocks, 5mm spacing (Jaycar HM3173, Altronics P-2032A) 3 3-way screw terminal blocks, 5mm spacing (Jaycar HM3172, Altronics P-2033A) 1 TO-220 mini heatsink, 6073B type (Jaycar HH-8502, Altronics H-0630) 1 6-way 2.54mm right-angle locking header (Jaycar HM3426; Altronics P-5516) – optional for ICSP 1 20MHz crystal (X1) Semiconductors 1 LM2940CT-5 regulator (REG1) (or use a 7805 – see text) 1 PIC18F4550/I-P microcontroller (programmed with 0510109A. hex (IC1) 4 BC337 NPN transistors (Q16Q19) 5 1N4004 diodes (D1-D3, D5-D6) 1 1N5819 Schottky diode (D4) 1 1N4148 diode (D7) – only needed for ICSP 1 16V 1W zener diode (ZD1) Capacitors 1 470μF 25V electrolytic 1 220μF 50V electrolytic 1 47μF 16V electrolytic 2 1μF 16V electrolytic 7 100nF monolithic (code 104 or 100n) 2 10nF MKT (code 103 or 10n) 2 22pF ceramic Resistors (0.25W, 1%) 1 56kΩ 10 10kΩ 4 22kΩ 6 1.5kΩ 2 33kΩ 1 10Ω 1W pleted, apply power (ie, via CON1). You should now see a message scroll past on the LED display modules. Among other things, this default wel­ come message should show the firm­ ware version. If you see this, then everything is working correctly and you can proceed to the next section which explains how to install the software driver on 68  Silicon Chip Display Board 1 PC board, code 05101092, 124 x 75mm 3 Kingbright TA12-11EWA dot matrix LED modules, red (Tenrod Cat. TA12-11EWA, Farnell Cat. 1168665) 3 14-pin IC sockets (cut into six 7-pin sockets to mount the displays) 2 16-pin IC sockets 1 SPST dome pushbutton switch (Jaycar SP-0657, Altronics S-1084) 1 32-way IC socket strip (Jaycar PI-6470, Altronics W-0420) 1 LDR (Jaycar RD-3480, Altronics Z-1619) 1 vertical USB Type B socket (Farnell 107-6666) Semiconductors 1 74HC595 shift register (IC2) 1 ULN2003 line driver (IC3) 15 BC327 PNP transistors (Q1-Q15) Capacitors 1 470μF 16V electrolytic 1 100nF monolithic Resistors (0.25W, 1%) 1 82kΩ 2 330Ω 15 690Ω 1 3.3Ω 0.5W Miscellaneous 4 M3 x 25mm Nylon screws (Jaycar HP-0142) 8 M3 x 12mm tapped Nylon spacers 8 Nylon flat washers (Jaycar HP-0148) 4 M3 x 6mm Nylon screws 1 1m length of tinned copper wire for links 1 200mm length medium-duty hook-up wire your PC. If not, you should refer to the troubleshooting panel. Driver installation The USB device interface for the Car Scrolling Display uses the generic Microchip driver for Windows. Before communicating with the display using the PC host program, you will need to install this driver. This section explains how to install the driver in Windows XP, although other versions of Windows will be similar. The first step is to download the Microchip installer (MCHPFSUSB_ Setup_v1.3.exe) from the S ILICON CHIP website and run it. Note that you should use version 1.3 as older or newer versions may not be compatible. The installer program will typically put the driver in the C:\ MCHPFUSB\Pc\MCHPUSB Driver\ Release folder. Next, connect the Car Scrolling Display to your computer using a USB cable. Windows will recognise the device as a “Display” and then the “Found New Hardware” Window will appear as shown in Fig.10. Select the “No, not this time” option and click “Next”. You will now be presented with a new dialog window. Select “Install from a list or specific location” and click “Next” again to bring up the dialog shown in Fig.11. Select “Search for the best driver in these locations” and enable the “Include this location in the search” box. Now click the “Browse” button. In the “Locate File” window that appears, navigate to where the MCHPUSB files were installed (normally C:\ MCHPFUSB\Pc\MCHPUSB Driver\ Release) and select “mchpusb.inf”. Click “Next” and Windows will then install the driver. If the driver is installed correctly, the “Microchip Custom USB Device” entry should now be visible if you go into Device Manager (Control Panel ->System -> Hardware tab -> Device Manager button) – see Fig.12 (provided the device is connected). Using the host software Once the driver has been installed successfully, you control the Car Scrolling Display using the PC host program cardisplay.exe. This program allows you to change all settings and to do data logging. It is also used for calibration. Once you’ve connected the Car Scrolling Display’s inputs to the sensors you are interested in monitoring, you can then use a laptop in your car to perform the calibration (you only have to do this once) or change any other system settings (such as the display brightness, etc). You can also use a laptop in your car to do real time data logging of siliconchip.com.au Fig.10: this is the dialog that appears the first time the Car Scrolling Display is connected to the PC. Select the option shown and click the “Next” button. Fig.11: selecting “Install from a list or specific location” brings up this dialog. Select the options shown and click the “Next” button. Windows then installs the driver. Troubleshooting Fig.12: this entry will appear in Device Manager if the driver is installed correctly. the signals. Of course, you will need someone else to do the driving while you do this! To install the PC host program, you first have to download the compressed file “cardisplay.zip” from the SILICON CHIP website (www.siliconchip.com. au). You’ll find it the downloads section under January 2009. Extract the files in the zipped archive to a folder on your hard drive. There should be at least two files: (1) cardisplay.exe – this is the executable command line program; and (2) cardisplay.map – this file is used siliconchip.com.au If the unit doesn’t work correctly, the following troubleshooting tips should help resolve the problem. Symptom: nothing is shown on the display or some columns or rows are blanked out. What To Check: there are a number of possibilities here. One is that CON6 and CON7, which connect the main PC board to the display PC board, are not making good contact. Try reconnecting the two boards to see if that clears the fault. Another possibility is that the Kingbright LED array modules have been installed with the incorrect orientation. If one column is blanked while the rest of the display seems to be working, then check its driver transistor – it may be faulty or it could be the wrong type (they should all be BC327 PNP types). Symptom: the supply rail is not close to +5V. What To Check: if the supply rail is 0V instead of +5V, check zener diode ZD1, reverse polarity protection diode D1 and regulator REG1. Check particularly that the diodes are all correctly oriented. If the supply rail is noticeably higher than +5V, there is either a problem with the regulator or a short between the 12V and 5V rails. Alternatively, a component connected to one of these rails may have failed (eg, diode D2 or D3). Symptom: the display seems to be working correctly but does not work when powered solely from the USB port. What To Check: either Schottky diode D4 is incorrectly oriented or the USB port (or hub) is not supplying power. internally by the host program. It must be in the same folder as cardisplay.exe for the program to recognise it. Note that the map file is produced by the C compiler of the firmware. It contains memory mapping information for the firmware produced by the linker. When and if the firmware is updated, the map file will also change and this new file must be copied to the folder containing cardisplay.exe in order for it to work correctly. So installing the PC host program is easy – just copy the cardisplay.exe and cardisplay.map files to your chosen folder. Once that’s done, you simply go to a command prompt to run the program using your chosen command line option. We’ll have more to say SC about this next month. January 2009  69