Issue 18: Apr 2002
Features
- | Foreword
- | Build your own Retro game
- | MIDIGEN
- | Tip of the day
- | Setting up a MIDI system
- | 8-bit vor 12 Party
- | Miniature Marvel
- | Activision's Pressure Cooker: Pre-processed Perils
- | Long Time Ago In A Galaxy Far, Far Away…
| Build your own Games Machine By Matthew Preston We never had a video game at home, but I remember playing Pong and Breakout at an after school club. I also remember putting coin after coin of my pocket money into a machine with a big yellow PacMan painted on the side. Those days are now gone, but we can recreate those memories by building our very own games machine that will plug into most television sets or video recorders. I recently came across such a kit quite by accident whilst browsing the latest Maplin Electronics catalogue. The Velleman kit entitled, "Classic TV Tennis Game", caught my eye as there was a small picture next to it which reminded me of Pong. At only ten pounds, I thought it was worth a go. A week or so later I purchased the kit from a local store and set about building it. I have built Velleman kits before and know from experience that they generally go together quite easily and have practically everything you need in the box. I have quite a bit of experience with amateur electronics and came across a number of stages that could potentially confuse the inexperienced builder. What follows is an account of how I went about building my kit and the pitfalls I encountered (which will hopefully enhance the documentation that comes with the kit should you decide to build your own). Before I begin, I would like to say that although the finished product is of excellent quality, it is not really a toy and should be treated as part of your computer collection. As a result, it's not something for the children to bash on. To assemble the kit, I you will need the following: Soldering iron 18-24 watt is enough with a small to medium sized tip. Solder The solder with the flux inside it is recommended. Try to make sure that you get the thinnest solder as possible (I use 0.7mm which should last you ages if you get a small reel of it). Solder station or stand with a damp sponge. A comfortable place to work with good lighting. Small pair of side-cutters. Cross-head screwdriver. Magnifying glass. Three AA batteries. Patience, lots of it! When you buy the kit you may wonder where the circuit-board is - I did. For some reason, it is hidden inside the packaging, along with the main instructions (so don't throw anything away). Before you begin, check that you have everything you need by looking through the instructions and familiarise yourself with all of the components. If you are new to building kits, Velleman have printed the best practice for soldering at the top of the instructions, however, I would recommend practicing before building your kit. This is exactly what you get Building the kit Begin by warming up the soldering iron, tin the tip by applying a little solder to the hot tip and wiping it gently across the damp sponge. You will need good eyes, I use a magnifying glass to check components as they are generally too small to read properly. Starting at stage one look down the list of resistors and solder each one to the circuit board in turn. I find it easiest to only take them from the strips as needed so as not to mix the components up. The resistors in place. Stage two, the diodes. Don't be mislead by the diagram, the first one is tiny, it also looks a bit like the Zener diodes in the next stage. To identify the required diode, take your magnifying glass and look very carefully at what is printed on them and how they are constructed. There is only one diode with the number 1N4148 and it is cylindrical in shape with a black bar at one end, quite different from the Zener diodes that look a bit like grains of rice with a silver crack in the middle. Make sure the black bar on the diode matches the white mark D1 on the circuit-board and solder it in place. The second diode D2 is huge by comparison and is quite easy to identify. This time however, the silver bar marks the polarity. Stage three, the Zener diodes. These are very small and there are four of them. Making sure that you observe which way round they go on the board and solder them in place. Stage four, the IC socket. This can be a tricky one if you have not soldered one before, as you must be quick with the iron or you will melt the socket. Making sure the notch on the socket matches the picture on the board and put the IC socket in place. Holding the socket turn the board over and place it flat on the bench. The socket should now be held firmly with the pins sticking out the copper side of the board. Start by soldering alternate pins on the socket and complete the four corners, this will hold the socket in place. Carefully complete soldering the rest of the pins and then use your magnifying glass to check that you have not accidentally made a solder bridge between any of the pins. The microprocessor is marked 121PAL and is copyrighted to Velleman. The component used is a Programmable IC, or PIC, number PIC16C505. They are quite robust but basic static precautions should be taken. The fascinating thing is that the IC has no real independent function, just inputs and outputs, the entire game, video and sound output is generated by the chip with pre-programmed software, amazing stuff. Bend the legs in a little and place it gently into the holder. When you are sure that all the legs are correctly placed, push the IC home. Stage five, push buttons. These are quite simple to push in place. Once you have done this, solder the legs to the board. Stage six, quartz crystal (this can be a little tricky). Push the long legs through the board leaving enough to lay the crystal flat. Bend out these legs slightly, this will stop the crystal from falling out of the board as you try to solder it to the circuit. Solder the small wire across the crystal as shown in the diagram to keep the crystal from moving. Stage seven, trim/potentionmeter. Push into place and bend the legs over on the copper side of the board, this will hold it firmly as you solder the component. Stage eight, capacitors. C1 and C2 have the number 18 printed on them, there is no polarity to observe just solder them to the board. Stage nine, electrolytic capacitors. The instructions indicate that they should be lay flat on the circuit, I found it easier to poke them through the board and bend out the pins so as to make them less awkward to solder. The polarity on these is very important, luckily they have the negative symbol printed quite large down one side, no chance of making a mistake here. Stage ten, LED. Take a close look at the instructions, you want the shortest leg nearest the LD1 label. Stage eleven. There are a couple of nice gold-plated sockets here, Push them in place, you want the outer most holes or they will keep falling out. Apply enough solder to the legs to hold them, don't flood the board with it. The build is almost complete, Stage twelve is a bit of a pain, mainly due to me having two left arms and being all thumbs. The exploded diagram gives the best idea, stick with it, it is very awkward to get the battery compartment to screw together properly. Your completed board should look like this; The completed kit. Playing the game You will need two phono leads to connect both the video and audio to a television. Also depending on the TV you may also need a Scart adapter, I have used the video inputs at the front of my video recorder next to my PC. The kit produces what is known as composite video output. Most new video recorders have this as standard, so if you have an old television this should not matter. With the television now on, put three AA size batteries into the holder on the kit. The circuit should burst into life, with a red glow from the LED. Don't be alarmed it the screen rolls, just press and release the reset button on the kit (don't expect colour, this is retro gaming). If you like, you can adjust RV1 marked brightness for a brighter picture, don't over do it or the screen may become unstable. For single playing, hold the left-up button and press then release the reset button. Push both up/down buttons to start and BIP! BIP! we're away. A screen-shot of the game as it will look on your television. To give you an idea of just how small the completed kit is, below is a photograph of my home system. I am a great fan of Atari and would love an original Pong machine. Sadly this is probably the closest I am likely to get, but for a tenner, it was great fun to build and is a joy to play.
Useful links
Velleman www.velleman.be www.velleman-kit.com Maplin Electronics If you are interested in building your own kit and live in the UK, the Classic TV Tennis Game kit can be purchased from Maplin (stock no. QP59P). www.maplin.co.uk Conrad Stores If you are interested in building your own kit and live in Germany, the Classic TV Tennis Game kit can be purchased from Conrad (stock no. 130374 - 62). Thanks to reader, Sebastian Kraus, for letting us know. www.conrad.de
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