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Build Your Own Poker Machine; Pt.2 Although it uses lots of parts, our new Poker Machine is very easy to build. Just follow the instructions below and you’ll soon be losing your shirt – metaphorically speaking, that is! By ANDERSSON NGUYEN As noted last month, this project is built on two PC boards: a main board (code 08112981) and a display board (code 08112982). The display board is mounted on top of the main board using 20mm spacers and machine screws and nuts. You can even mount the completed assembly beneath a perspex sheet or in a wooden case, if you wish. In all, there are 35 ICs on the two 54  Silicon Chip PC boards and 33 of these are CMOS types. This means that you should take care to prevent damage to the devices by static electricity. Always leave the devices in their antistatic packaging until you are ready to solder them into circuit and avoid touching any of the pins. Provided you exercise reasonable care, you shouldn’t have any problems but if you’re really cautious, you can invest in an antistatic wrist strap. Before installing any of the parts, go over the two etched PC boards carefully and compare them with the published patterns (Fig.5). It’s much easier to locate and fix any defects at this stage than after all the parts have been installed. You will need a soldering iron with a fine tip for this job, since many of the pads and tracks are in close proximity to each other. The use of IC sockets is optional. They make it easy to change a suspect IC but they also add to the cost. Usually, you can solder the ICs straight in without any problems. Building the main board The assembly can start with the main board – see Fig.3. Begin by in- sure that the electrolytic capacitors are correctly oriented and note that several of the resistors (R5, R6, R13 & R14) are mounted end on. The transistors and diode D2 (1N4004) can go in next. Again make sure that they are correctly oriented and make sure that transistors Q9-Q12 are BC337s. Now for the ICs. These can all be installed in their cor­rect locations, noting particularly that IC22 (555) faces in the opposite direction to the other ICs. Pin 1 of each IC is identi­fied by a small notch or dot in the plastic body at one end. Do not touch any of the IC pins. If you need to bend them so that they go in the holes, just push a row of pins along one side against the top of the bench (but do it gently). The buzzer is attached to a vacant spot on the PC board (see photo) using double-sided adhesive tape. Alternatively, you can glue it in place using a small dab of epoxy adhesive. The leads of the buzzer are then soldered to the PC board, or you can terminate the leads on a couple of PC stakes if you wish. External wiring Fig.3: install the parts on the main board as shown in this wiring diagram. Note particularly that IC22 (555) faces in the opposite direction to the other ICs. stalling the numerous wire links, then install the resistors and capacitors. The accompanying table shows the resis­tor colour codes but it’s also a good idea to check the resistor values using a DMM, just to make sure. Make Once all the parts are in, you can add the external wiring leads. Begin by cutting four 8cm lengths of 7-way rainbow cable plus a 10cm length of 8-way cable. The four 7-way lengths are connected along the top of the board adjacent to the 4511 display drivers, while the 8-way cable is soldered to the righthand side of the board near the buzzer. We terminated the 8-way cable in a ribbon cable header and this plugs into a matching pin header on the display board. However, these parts are optional and you may elect to save money by soldering the 8-way cable directly to the display board in­stead. The 8-way cable, by the way, connects to the bases of transistors Q1-Q8 on the display PC board. Another lead is also run from pin 11 of IC23 to the display board, where it connects to pin 13 of IC34. The pad for this lead is immediately to the left of the pads for the 8-way cable. This lead can also be about 10cm long and can be run using light-duty hookup wire. The assembly of the main board can now be completed by fitting the leads for the Play switch (S1) and for December 1998  55 Use red for the positive supply lead and black for the negative. Display board assembly Fig.4 shows the display board assembly. As before, start by fitting the wire links, then install the resistors, capacitors, transistors and ICs. The transistors (Q1-Q8) are all BC548 types and they all face in the same direction. Note that many of the resistors are mounted end-on to get them to fit. Note also that a wire link goes between the two resistors directly below DIS9 – you have been warned! Next, fit the 1N5404 reverse polarity protection diode, taking care to ensure that the banded end goes towards the dis­plays. R29 and R30 can be omitted if you don’t want the decimal points on DIS8 & DIS11 to light. The LEDs can be mounted next, taking care to ensure that their anode leads go to the “+” terminals (the anode lead is the longer of the two). Note that LEDs 1, 2 & 3 are green, LEDs 4 & 5 are orange and LEDs 6, 7 & 8 are red. The 7-segment LED displays can now be installed. This is straightforward; just remember that the decimal point of each display goes towards the bottom right. Push each display down onto the board as far as it will go before soldering its leads. Note that four wire links go under the large displays so make sure that these are in position before mounting the displays. Finally, complete the display board assembly by installing PC stakes at the power supply terminals (two at top right for the plugpack leads and two at bottom left for the supply connections to the main PC board). You should also install the pin header if you intend using this optional part. Final assembly Fig.4: the parts layout for the display board. Make sure that all the displays are correctly oriented. The resistors marked Rx and Ry are all 330Ω. the power supply. These leads are terminated on PC stakes and should be run using medium-duty hookup 56  Silicon Chip wire. The leads for the Play switch can be about 160mm long, while the supply leads can be about 80mm long. Once the display board assembly has been completed, connect all the leads from the main PC board. These leads are as follows: (1) the four 7-way cables to the large 7-segment displays; (2) the 8-way cable to the bases of Q1Q8; (3) the lead that runs from pin 11 of IC23 to pin 13 of IC34; and (4) the supply leads to the output terminals at bottom left (ie, adjacent to IC33). Take extra care when connecting the supply leads between the two boards. The positive terminal on the display board (near IC33) is the topmost terminal. Conversely, the positive terminal is the bottom-most Repeated from last month, this photo shows the completed PC boards just before they are stacked together. Ignore the wire links shown on the back of the display board – we changed the PC pattern to eliminate these for the final version. of the supply terminals on the main board. Do not get them mixed up, otherwise you could damage some of the semi­conductors. With the wiring completed, the two boards can be stacked together and secured using 20mm spacers and machine screws and nuts. It would be a good idea to fit small rubber feet to the bottom of the display board, so that it doesn’t scratch the desktop. Alternatively, you might like to build the assembly into a wooden case, with a clear Perspex window for the LED displays. The Play switch can be suitably mounted on the front panel. Testing & operation Power for the circuit comes from a 9V 1A plugpack supply (do not use a 12V supply, as this could damage the displays). Connect the supply leads to the terminals on the display board (at top right), apply power and check that the LED displays come on. Initially, the large 7-segment displays will display a random result. The digits may all be off, cycling or stationary; or you may have a mixture of these conditions. The smaller 7-segment LED displays (ie, the scoreboard arrays) should all initially display “0”, while the LED score indicators at bottom right should all be off. Now press the Play switch. The large displays should imme­ diately begin cycling and the transducer should produce a rapid clicking sound to simulate the sound of the “rolling barrels”. After a short period, the displays should slow down and eventual­ly stop, starting with the most significant digit and finishing with the least significant. Note that the first “play” will take some time to come to a stop, due to the way the circuit works. Subsequent plays will finish much faster, so be patient the first time around. If it all works so far, press the Play button a few more times until you get a winning combination. When this happens, check that the corresponding indicator LED flashes and that the credits are incremented on the scoreboard displays. For example, if you get a pair, LED 1 should flash and the scoreboard should increment by 1. Similarly, if you get two pair (eg, 6633), LED 3 should flash and your score should increment by 100. If you get four of a kind, the decimal points should chase, while 0000 or 8888 will result December 1998  57 Resistor Colour Codes  No.    4    1    2    1    1    4    1    1    1    1    1    8    2    1    6  64 Value 10MΩ 680kΩ 560kΩ 470kΩ 150kΩ 100kΩ 82kΩ 62kΩ 56kΩ 47kΩ 33kΩ 22kΩ 15kΩ 1.2kΩ 390Ω 330Ω in all the digits flashing on and off. Table 1 in last month’s issue shows the winning combina­ tions and the results. Note, however, that a small error crept into the table. The example given for a “Pair In A Pair” winning combination should read XYYX and not XYYZ). Troubleshooting If the circuit appears to be working but one or more of the segments on the large displays is missing, check the wiring to the displays between the two boards. It’s possible that one of the leads may have broken. If the wiring is OK, check for breaks in the copper tracks at the display driver outputs (pins 9-15 of IC1, IC3, IC4 and IC6 on the main board). In 4-Band Code (1%) brown black blue brown blue grey yellow brown green blue yellow brown yellow violet yellow brown brown green yellow brown brown black yellow brown grey red orange brown blue red orange brown green blue orange brown yellow violet orange brown orange orange orange brown red red orange brown brown green orange brown brown red red brown orange white brown brown orange orange brown brown addition, check for breaks in the tracks to the display segments on the display board. For example, if segment “f” of display 4 (DIS4) fails to light, check the circuit from pin 16 of IC6. If a digit fails to light, check that its common connection (pin 1) is connected to the earth pattern. Note that although the circuit shows pins 1 and 5 of the displays connected to ground, only pin 5 is connect­ed on the board. In fact, it’s a good idea to run an insulated link between pin 1 and the nearby earth pattern on the PC board, to make the earthing more secure. If the connections are OK, check the supply voltages on the relevant display driver and check its outputs. Similarly, if you have trouble with Silicon Chip Binders   Heavy board covers with 2-tone green vinyl covering   Each binder holds up to 14 issues  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A12.95 plus $A5 p&p each (Australia only; not available elsewhere). Buy five and get them postage free. Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. 58  Silicon Chip REAL VALUE AT $12.95 PLUS P & P 5-Band Code (1%) brown black black green brown blue grey black orange brown green blue black orange brown yellow violet black orange brown brown green black orange brown brown black black orange brown grey red black red brown blue red black red brown green blue black red brown yellow violet black red brown orange orange black red brown red red black red brown brown green black red brown brown red black brown brown orange white black black brown orange orange black black brown the scoreboard dis­ plays, check the segment driver outputs from the 4026s (IC24-33). If the count jumps about or if the wrong segments light up, check for shorts due to solder bridges between pads or tracks on the copper pattern. A count that stops abruptly instead of slowing down is almost always caused by a static-damaged 4046 IC. These ICs are particularly prone to static damage and should be replaced if you have any doubts. If there are other problems, check the two boards carefully for missed solder joints and other soldering errors. You should also check that all the parts are in their correct locations and that you haven’t left out any wire links. It’s also a good idea to check the supply voltages to all the ICs. If any of the supply voltages is missing, then you’re halfway to tracking down the problem – just backtrack along the supply rail to find out where the problem occurs. Laws of probability Once complete, the circuit will provide you with hours of fun without costing a cent more. Obtaining a pair or even two pair is relatively easy but three of a kind is much more diffi­cult. You’ll also quickly realise just how difficult it is to get four of a kind, let along four eights or four zeros. Fig.5: the PC etching patterns have been reproduced here 71% of actual size. You can get full-size patterns by copying them on a photocopier set to a standard 1.41 enlargement factor. Probability is indeed against you and you’ll soon realise that with a real poker machine, which general- ly has five digits and more than 10 possibilities for each, the chance of a favour­able combination is highly un- likely. Hopefully, this will dis­courage you from throwing your money away on them. SC December 1998  59