June 2014
Table of Contents 1 Overview Features Applications 3 3 3 2 Assembly Hints 4 3 PCB Overview 5 4 Circuit Diagram 6 5 Assembly Diodes and IC socket Electrolytic capacitors Ceramic capacitors 10K resistors 68K resistors 100K resistors 220K resistors Remaining resistors Arduino headers Power transistors NPN transistors PNP transistors Tube backlighting LEDs VFD tube mounting 7 7 7 8 8 8 9 9 9 10 10 10 11 11 12 6 Final Test 13 7 Legal Information Disclaimer Trademarks 14 14 14 8 Contact Information 14 Revision History Date Authors 2014-06-10 Ilse Joostens 2 Description Initial release.
1 Overview This Arduino shield is capable of driving 4 Russian IV-3 7 segment VFD tubes. 4 3mm LEDs provide background lighting for the tubes. The design is completely based on through hole components, no SMD components were used. As such, the PCB can easily be assembled by anyone who has some soldering experience. Also, the components used are cheap and easily available. As this was designed as a more educational, easy to build project it is not the best possible solution to drive these VFD tubes from a technical point of view. Instead of the BC547 and BC557 transistors we could have used A2982W source drivers, or we could have replaced the transistors by a Supertex high voltage source driver IC with internal shift register. Unfortunately these may be hard to get and come very often in SMD packages. Features Compatible with Arduino boards. Drives 4 IV-3 VFD tubes. Power supply 12V DC + 5V DC (from Arduino board). Enclosure design (CAD files) available. Applications Clock. Score board. Thermometer. Counter. 3
2 Assembly Hints This kit is designed for someone who has advanced experience with assembling electronics. If you believe that the kit is too complicated for your skill level please do not try to assemble it. Take your time - this kit should take 2-3 hours to complete if uninterrupted. Ensure your work area is well lit (daylight preferred) and clean. Assemble the board in the order as stated in the instructions - read and understand each step before you perform each operation. It is assumed that you understand that semiconductors (diodes, ICs, transistors) and electrolytic capacitors are polarized components. Appropriate markings are silk-screened on the PCB and shown on the board schematic. The following tools and materials will be required to assemble the PCB: A good quality soldering iron (25-40W) with a small tip (1-2 mm). Wire cutter and pliers. Basic multimeter for voltage tests and for identifying the resistors. A magnifying glass to read the small device markings is often helpful. Solder lead / tin solder is preferred. Lead free solder, as now required to be used in commercial products in Europe, has a much higher melting point and can be very hard to work with. Do not use any flux or grease. Desoldering wick (braid) can be useful if you accidentally create solder bridges between adjacent solder joints. Power supply The IV-3 VFD shield needs the Arduino to be powered from a 12 V DC power supply to function properly. Use a regulated switching power adapter capable of delivering 12 V DC / 300 ma. Do not use an unregulated "transformer style" wall adapter. These deliver easily more than 16 V with a light load and will cause damage to the IV-3 VFD shield as the 12 V supply voltage is quite critical. Put some insulating tape on the metal shield of the USB connector of your Arduino before connecting the IV-3 shield to avoid solder connections touching the metal and being shorted. 4
3 PCB Overview 5
4 Circuit Diagram 6
5 Assembly In the following pages we are going to assemble the PCB step by step. It may be helpful to keep the PCB overview and the circuit diagram at hand during assembly. After every step, carefully compare your PCB with the pictures in the manual and check for errors and solder faults. Diodes and IC socket Mount the following diodes: D1: 1N400x or equivalent D2...D5: 1N5819 schottky diode Watch the polarity and be careful to mount the right diode in the right place. Solder D2 and D3 from the component side and trim the wires on the solder side as short as possible as they are positioned above the metal USB connector shielding of the Arduino. Mount the 8 pole IC socket for IC1. Do not place IC1 in the socket at this stage. Electrolytic capacitors Mount the following electrolytic capacitors: C5...C8: 22µF 50V radial electrolytic capacitor C9, C10: 100µF 25V radial capacitor Bend the leads 90 degrees and mount the capacitors flush to the PCB. Watch the polarity. It is recommended to solder C6, C7 and C8 from the component side and to trim the leads as short as possible on the solder side as they are positioned above the metal shield of the Arduino USB connector. 7
Ceramic capacitors Mount the capacitors: following C1: 2n2 C2, C3: 8n2 C4: 100n ceramic Please note that the values of C1...C3 are somewhat critical as C1 defines together with R5 the operating frequency of the voltage tripler and C2, C3 define the filament current for the IV-3 tubes. 10K resistors Mount the 10 kilo ohm resistors (brown black orange gold) R6...R18. Mount them vertically as shown in the picture. 68K resistors Mount the 68 kilo ohm resistors (blue grey orange gold) R19...R30. Mount them vertically as shown in the picture. 8
100K resistors Mount the 100 kilo ohm resistors (brown black yellow gold) R31...R42. Mount them vertically as shown in the picture. 220K resistors Mount the 220 kilo ohm resistors (red red yellow gold) R43...R54. Mount them vertically as shown in the picture. Remaining resistors Mount the remaining resistors: R1: 510 ohm (green brown brown gold) R2, R3: 1 kilo ohm (brown black red gold). You may need to adjust the value depending on the tube backlight LEDs you plan to use. R4: 2.7 kilo ohm (red violet red gold) R5: 3.9 kilo ohm (orange white red gold) 9
Arduino headers Mount the Arduino stackable headers. The headers will not really be used to stack other Arduino shields on top of this shield but they help to determine the mounting height of several components and the IV-3 tubes. Push the headers through the PCB and plug them in your Arduino. Turn upside down and solder 1-2 pins for each connector. So the connector spacing will be correct. Remove the shield from the Arduino and solder the remaining pins. Power transistors Mount the following transistors: T26: BC639 T27: BC640 Do not replace these transistors with standard types. Mount them so that the top of their housings is lower than the Arduino headers. Insert IC1 ICM7555 into its socket and plug the shield into an Arduino and apply power. The voltage measured between the cathode of D5 and the Arduino ground should be around 32...34V NPN transistors Mount the BC547B transistors T1 T13. Mount them so that the top of their housings stays below (or is flush with) the Arduino headers. 10
PNP transistors Mount the BC557B transistors T14 T25. Mount them so that the top of their housings stays below (or is flush with) the Arduino headers. Tube backlighting LEDs You can use 3mm standard LEDs in any color for tube backlighting purposes, even RGB color fading LEDs. Bend the leads of the LEDs so that the LEDs fit in the 3mm holes underneath the VFD tubes, then solder them to the pcb. Pay attention to polarity. The short lead of the LED (cathode) is soldered to the pad closest to the LED name silk-screen marking (D6 D8). It may be necessary to insulate the leads of D9 to avoid them touching the ISP connector on the Arduino. The LEDs are connected to a PWM output on the Arduino and can be dimmed using software. This will however not work properly when you use RGB color fading LEDs. If it is easier for you, it is also possible to mount the LEDs after the VFD tubes are soldered in place. Due to the mounting technique, it is also easy to replace the LEDs later on if you decide you would like to have another backlighting color. 11
VFD tube mounting Guide the tube wires gently through their respective holes on the PCB. Make sure the short lead on the tubes goes through the hole without solder pad. Now the digits should face the front of the PCB. If you have difficulties getting the wires of the tubes through the holes you can cut them as a "spiral" so you can move 1 wire at a time through the holes. Pay attention to make the shortest wire not too short as we are going to mount the tubes with some distance from the pcb. Once the tubes are in place align them more or less by hand. The bottom of the tubes should be approximately 1-2 mm below the top of the Arduino stackable headers. If you are using the optional acrylic enclosure, you can use the top and bottom plates as an alignment tool. Solder two leads of each tube to the PCB. Once this is done, you can still adjust the tube alignment by reheating the solder joints. If you are satisfied with the tube alignment, you can finally solder the remaining tube wires in place and trim the excess leads with a small wire cutter. Do not try to change the alignment of a tube after it is soldered in place as this may cause mechanical stress and may lead to a defective tube. 12
6 Final Test Upload the demo sketch from the Axiris website to the Arduino and disconnect the Arduino from the computer's USB port. Plug the finished IV-3 VFD shield on top of the Arduino. Make sure no metal part of the Arduino touches the solder joints of the IV-3 VFD shield. Connect the 12 V DC power adapter to the Arduino power connector and turn the power on. After a few seconds the VFD tubes should start counting from 0 to 9 in an endless loop. The decimal separator dots of the VFD tubes should form a binary 4 bit counter. Tube backlighting should dim and turn on again every few seconds. Check the tube filament wires carefully. They should glow very faintly with a deep red color. If they are glowing too much, lower the values of C2 and C3. On the other hand, if the filament barely glows and the digits are too dim, you can experiment by increasing the values for C2 and C3. 13
7 Legal Information Disclaimer Axiris products are not designed, authorized or warranted to be suitable for use in space, nautical, space, military, medical, life-critical or safety-critical devices or equipment. Axiris products are not designed, authorized or warranted to be suitable for use in applications where failure or malfunction of an Axiris product can result in personal injury, death, property damage or environmental damage. Axiris accepts no liability for inclusion or use of Axiris products in such applications and such inclusion or use is at the customer's own risk. Should the customer use Axiris products for such application, the customer shall indemnify and hold Axiris harmless against all claims and damages. Trademarks All product names, brands, and trademarks mentioned in this document are the property of their respective owners. 8 Contact Information Official website: http://www.axiris.eu/ 14