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! Come in r !! e r e n n i SSpppi n S S SS ppi r SSppiinnnnneee SSppiinin eerrr SSSp ! S SS pi SSppiinnnne r!! e ! r r ! ! No, it’s not our version of the great Aussie game. This “Spinner” is one of the simplest projects we’ve ever published – yet also one of the most intriguing. It writes messages in thin air as you spin it! It’s very easy to build, costs very little and makes a great “first project”. W ith just 13 components and a couple of switches to solder in place, this project is about as simple as projects can get. Yet it will amaze you and all who see it in operation. Messages seem to write in mid-air when you give it a spin! There is no motor to spin the Spinner – it is operated by finger power. All you do is set the message you want to display by appropriate switch pushes, then flick the message stick on its axis so that it spins. There are two parts to the Spinner: the message stick itself, which contains all the components, and a handheld battery pack which also provides the axle on which the stick can spin. The axle is a little unusual – it is in fact a 3.5mm phono plug mounted in the end of the battery pack. On the stick is the matching 3.5mm phono socket. When you “plug” the battery pack onto the message stick’s socket, as well as creating the spinning mechanism you’re also supplying power to the system. Clever, eh? But wait, there’s more! Attached to the back of the PC board, close to the axle, is a short 32  Silicon Chip length of fairly thick tinned copper wire, almost (but not quite) long enough to touch the surface of the end of the battery holder as the board is spun around. Secured across the end of the battery holder is another length of tinned copper wire, just high enough to be hit by the wire sticking out from the PC board. So as the PC board is spun around, once every revolution these two wires touch. This tells the circuit to dump the contents of the on-board memory (actually a small PIC microcontroller chip) which in turn tells the LEDs to light up in certain patterns. If the board is spun slowly, all you will see is a line of glowing LEDs for a short time and then nothing. But if it is spun at a reasonable speed and in the right direction (by giving it a good flick with your finger) the LEDs are moving as the micro­ controller instructs them to turn on and off. Like the moving message display Design by Attilla Aknar* Words by Ross Tester board we featured last issue, the LEDs spell out a message. In fact, there is not really a message at all but the eyes, with their persistence of vision, “remember” how the LEDs glow over the course of their travel and that’s how the message is produced. And all this appears to happen “in space” – the spinning PC board moves too fast to be focused on (it actually appears as a blur) but the eyes (and the brain) remember the message as if it was really there. The length of the message (not the number of letters but the actual width of the letters around the arc) depends on the speed of the spinning PC board. If you spin it really quickly the message can occupy a significant proportion of the circle. As it slows down (which of course it must do due to friction) the letters become thinner and thinner. Eventually (as the spinning stops), the whole message is displayed in the width of one LED – or 5mm. This is of course completely unreadable. The messages There are three different spinners available, depending on which PIC Look mum, it’s magic! This photo is not retouched – the image that you see is part of the image that we saw written “in space” (it happens to be the designer’s name but it has been abbreviated a bit by the length of time the camera shutter was open – about 1/8 second). With a good swift flick, the message can occupy a good 180° of arc. chip is supplied (each contains different programming. First is the Spell Spinner which displays each letter of the alphabet and a word beginning with that letter (eg, A APPLE, B BOY, C CAT and so on). Pressing the up and down pushbutton switches advances the message one letter. The third switch is not used in this, or the next Spinner. Second is the Message Spinner which has ten different messages programmed (some examples are shown below). Stepping between the messages is also done with the up/ down push buttons. Finally there’s the Programmable Spinner where you enter your own message with the up and down pushbutton switches. As you enter each letter of your message, you place it in memory by pushing the third switch. It will take you a while, because each press of the switch advances one letter of the alphabet. So if you want to program in a message saying “MY NAME IS XERXES” you’re up for about 200 button presses! (Lucky you if your name is ABE – only about 110 button presses!!!) Construction As the chances are that this could be your first project, we’re going to cover this section in much more detail than normal. First, examine the PC board closely (you might need a magnifying glass for this). Check to see if there are any broken tracks or if any points are bridged together. We’ve published the full-size PC board pattern to help you do this, Some of the messages displayed in version two of the Spinner. Another six or so are accessed by pressing the up/ down pushbutton switches. August 2000  33 There’s not much to it, is there? A PIC microcontroller, five LEDs and a few other components make up The Spinner. The messages depend on which PIC you use. though with a board like this (which has very fine tracks and close track spacing) making a board yourself (at home, school, etc) is pretty much out of the question. Besides, the PC boards have been priced very well to make it a cheap kit to buy. Having satisfied yourself that the PC board is as it should be, it’s time to start inserting and soldering components. Start with the five 100Ω resistors. These 1/10W resistors are much smaller than the 1/4W resistors we normally use in projects so require a little more care than normal. All of the resistor leads should be bent up 90° so that each resistor forms a “U” shape with the verticals exactly 7mm apart and parallel, with the resistor body itself across the bottom of the “U”. The components all mount on the side of the PC board opposite to the copper tracks. They do not need any glue or other method of holding in place because their legs or leads poke through the board and are soldered to the copper pads. (If you’re not new to this, don’t laugh – we all had to start somewhere. And we’ve seen some beautifully constructed PC boards with the components all carefully glued in position on the copper side of the board with not a milligram of solder to be seen!!!) Place the resistors in their appropriate holes one by one, soldering them as you go. Because of the extremely fine tracks and tiny pads on this board it’s easy to damage it with too much heat from your soldering iron. Ideally, you need a fine to very fine tipped iron (with the tip itself clean and well tinned), preferably temperature controlled. If you haven’t soldered before, practise with some other components or hook-up wire before soldering the board. When you’re ready, apply only as much heat from the iron as necessary to make the solder flow evenly around the resistor lead, securing it to the pad underneath. By the way, make sure the solder you use is intended for electronics applications. The solder you buy at your local hardware store is probably not suitable – it often contains flux which is corrosive. Having successfully soldered the resistors, now try the five LEDs. These are polarised devices – if they are inserted back to front they won’t work! Notice how the LEDs have one flat side on them? This marks the cathode (or negative side), usually identified with the letter “K”. The flat sides of the LEDs ALL go towards the centre of the PC board. Also, there are extra pairs of holes on the board for different components which we don’t use here. Make sure you get the two leads from each LED into the right holes and the right way around! Incidentally, you may be wondering why we use a “K” for cathode and not a “C”? Two reasons: transistors, as you may know, have three leads – the emitter, base and collector (or E,B and C). Using “C” for a cathode might confuse it with a “C” for collector! Secondly, the German word for cathode is kathode – so we use a K instead of a C. This applies to all diodes, not just LEDs (which is short for Light Emitting Diode). We’re going to leave the integrated circuit (or IC) until last but there is Use the photograph, component overlay and PC board pattern to help you build any version of The Spinner. The PC board pattern above is as seen looking at the back of the board while the component overlay above that again is as seen if you had X-ray vision and could see the copper tracks through the board from the component side. 34  Silicon Chip Side-on view of the acrylic battery holder which doubles as a handle. The 3.5mm plug emerging from the right end supplies power and is also the axis on which the PC board turns. This, and the trigger wire, can be clearly seen in the end-on shot at right. no reason why you cannot solder in its 8-pin socket now. Note that the IC has a notch in one end and so does the socket. This allows you to work out which is pin 1. With the IC (or socket) held upright with the notch at the top, pin 1 is always the top pin on the left side. The pins then number down the left side (in this case 1,2,3,4) and then up the right side, 5,6,7,8 from the bottom as you are holding it. OK, put the IC aside for a while and very carefully solder in the socket so that its notch is towards the centre of the board. Again, be very careful – some of the very fine copper tracks go between the IC socket pads. While they are covered with a green solder mask (which protects the tracks and helps keep solder away) it is possible to solder across the tracks. We’ll ignore the trigger pick-up and 3.5mm socket for a moment and solder in the small (0.1µF) ceramic capacitor next to the IC socket and the 100µF Another view of the trigger wire and its pickup, this time in a close-up photo of the assembled Spinner. electrolytic capacitor on the other side of where the socket will mount. You will note from the photographs that this capacitor is lying on its side. It’s not vital that this is done but laying it over like this reduces the overall height of the PC board, making it less likely to snag or catch anything else while spinning. What is important is the polarity: electrolytic capacitors must be connected the right way around, otherwise they can actually explode, spreading gunk far and wide (and it’s not good stuff to get in your eyes!). This may not happen immediately but it will happen. Electrolytic capacitors normally have a stripe down one side in which there are “–” (minus) symbols. The lead closest to this is the negative lead. The other lead is obviously the positive lead (+) and on some PC boards you might find only a + symbol. This PC board fortunately has both + and – identified so it’s even harder to make a mistake. The final component to solder in is the 3.5mm socket. This mounts through the PC board from the component side with a nut securing it in place on the copper side. However, that’s not all that’s required: you also need to connect two of the three terminals on the socket to the PC board. The easiest way to do this is use some short lengths of wire which you’ve cut off resistor or capacitor leads (often called pigtails). These simply solder between the socket terminals and the PC board below. Note though which way around the socket goes. It has two terminals on one side and one on the other – the two terminal side faces towards the IC socket. The terminal closest to the PC board (on the two terminal side of the socket) and the single terminal on the other side are the ones to connect to the Parts List – Spinner Message Stick 1 PC board, 285 x 14mm, coded SpinStick V1.0 1 3.5mm mono phono socket, chassis mounting 1 3.5mm mono phono line plug (no cover) 1 8-pin DIL IC socket 3 mini pushbutton SPST momentary contact switches, PC mounting (2 only required for spell or message versions)* Semiconductors 1 12C509A PIC micro, programmed in one of three ways* 5 ultrabright red LEDs, 5mm Capacitors 1 100µF 16VW PC mounting electrolytic 1 0.1µF ceramic Resistors (1/10W, 5%) 5 100Ω (brown-black-brown-gold) Miscellaneous 1 clear acrylic tube, 133mm long, 38mm OD with end-caps 1 8mm length stiff solderable wire for trigger (eg, bronze)* 1 30mm length stiff tinned copper wire* 1 4xAA battery holder (flat style) 4 AA batteries *SEE TEXT August 2000  35 board. You don’t need to solder the third terminal because this is actually a switched terminal, disconnected when a 3.5mm plug is inserted. We said that the socket was the final component, which is strictly true. But we still need to solder in the trigger “pickup”, a short length of heavier-gauge tinned copper wire. Using resistor or capacitor pigtails here would be futile because they would bend too easily and so not make reliable contact. You need to have about 7mm of wire protruding from the copper side of the board. We used a length of wire a bit over 10mm with the remainder protruding from the top (component) side of the board. This can be used as a test point later on to check triggering. The wire we used was a tight fit in the PC board hole – again, this adds strength to the pickup. You will note from the component overlay that the mounting point is closest to pin 1 of the IC. Once soldered in, we bent the wire towards pin 8 at about a 45° angle. This can be adjusted later to ensure a contact is made. Finally, carefully insert the IC into its socket, making sure the notched end in the IC matches the notched end of the socket and that all eight pins correctly mate with their socket contacts. The “handle” The other section of the Spinner is the acrylic handle, which contains the batteries (4 x AA in a battery holder) and houses the 3.5mm plug on which the PC board spins. This plug mounts through one of the end caps in the exact centre. Alongside is a loop of tinned hookup wire which lies flat across the end cap and is connected to the negative battery lead. This is of course what the trigger contact “wipes” over each rotation, triggering the message. Start assembly of this section by finding the exact centre of the end-cap with all of the holes in it (the other end cap is plain). Drill a 5mm hole in this end cap. The 3.5mm plug, without its plastic cover, screws into this cap from the outside. There is a thread on the 3.5mm plug which will tap into the plastic of the 36  Silicon Chip the two ends together and solder them to the negative battery lead/3.5mm plug body terminal. Push the other end-cap onto the acrylic tube, slide the battery connector (with four AA cells) in the other end (it’s a tight fit) and finally push the end-cap and 3.5mm plug assembly onto the tube. That completes the assembly – all that remains is setting the trigger wire and checking that it works. Finishing off end-cap making it a snug fit but for security, once all soldering is done, a dob of glue (contact adhesive or similar) over the back of the plug will help hold it in place. Solder the red lead from the battery holder to the centre pin terminal of the 3.5mm plug and the black lead to the body terminal. Next, pass a length of tinned copper wire through one of the holes in the end-cap, wrap it over the edge, across the front back and through the same hole. Fashion this right into the edges of the cap with fine-nose pliers. Solder Push the Spinner PC board 3.5mm socket all the way onto the 3.5mm plug on the handle. Angle the trigger wire until it just clears the surface of the end cap but hits the tinned copper wire each time it passes over it. There is enough spring in the trigger wire to ride over the tinned copper wire and return to the same place. (Obviously, you can only turn the Spinner one way because turning it backward – ie, anticlockwise – will cause the trigger wire to snag). As you make the adjustment, you should find the LEDs flash each time the trigger wire contacts the wire on the end cap. If it does, your Spinner should be working properly. Now hold the handle firmly with the Spinner facing you and give the PC board a good flick in the clockwise direction (you’ll get the best spin by flicking as close as you can to the handle. You should be able to read the message displayed even though you can’t see the PC board. Depending on the version you’ve built, pressing the programming switches (as detailed above) will change the displayed message up or down or let you enter your own. Now you’re ready to amaze your SC family and friends! Where do you get it? The Spinner was designed by 4D Systems Pty Ltd, who hold copyright on the PC board, the design and on the program residing in the PIC. A complete kit of parts is available from 4D Systems for $24.95 (including GST) plus pack and post. Don’t forget to specify which type of Spinner you want. 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.