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Have fun with the Fruit Machine Step right up, folks. Try your hand at the amazing Fruit Machine. You can use it just like a poker machine but you don't have to go home in the evening flat broke. There is a jackpot and other winning combinations. Design by BRUCE BAGULEY "Gambling is a curse" , they say and it certainly sends many people broke every week. Whether you enjoy playing poker machines or wish to demonstrate their futility, you can have fun building and playing with the Fruit Machine. It is economical to build and requires no coins to be fed into it to play! Designed by Bruce Baguley, of Kotara High School in NSW, the Fruit Machine is also a good exercise in electronic principles. It uses timers, counters and decoders to drive three ?-segment LED displays. The LED displays are not wired to show digits but to show letters of the alphabet. As wired, they can show "A" (for Aces), "O" (for Oranges), "C" (for Cherries) and "L" (for Lemons). There is one jackpot combination and five other winning combinations of these displays. The jackpot is three Aces (AAA) which, according to the front of the Fruit Machine, gives a payout of 1000 points. No money changes hands, of course, but it is nice to keep score. Other winning combinations are as follows: 000 (3 Oranges) - 150 points; CCC (3 Cherries) - 20 points; LLL (3 Lemons) - 10 points; and AA (2 Aces - 5 points. All other display combinations are losing, which is to say that they don't win any points. Sad. Ergonomic features As presented by the designer, the Fruit Machine is built into a small wooden enclosure which looks like a miniature poker machine. There is a long lever on the righthand side to play the unit but apart from that, there is no on/off switch or any other controls. The front panel has the three red LED displays in a transparent window and the winning combinations are printed for easy reference. All you have to do is plug in a 12V DC plugpack and you are ready to play (but not lose your shirt!). The circuit The circuit of Fig.1 looks pretty large but it is basically a smaller circuit repeated (almost exactly) three times. So to fully describe the whole circuit, we only have to describe a third of it. So let's have a look af the top section of the circuit, The prototype was built into a small wooden case & fitted with a handle, just like real pokies used to have. You can play it just like the real thing but it won't send you broke. 22 SILICON CHIP Fig.1 (right): the circuit consists of three almost identical sections, each based on a 555 timer, a 4017 decade counter & an FND500 7-segment display. When the play button is pressed, the 555 timers clock the decade counters & these then drive the segments of the displays via decoding diodes & driver transistors. + 270k_ 16 V+ 390!! 390!! 390!! 3 14 IC2 4017 a 03 BC548 E 6 C1 01! ef d fc FND500 2d 05 BC548 E 15 .,. + a 4C 04 BC557 C 13 ,,-:-,b 6 b 10 .., 16 470k 390\! 390U 390\! 14 IC4 4017 08 BC548 E 6b 4C FN0500 0.1 ! +12VO FROM PLUG-PACK 09 BC557 C V+ 01 1N4002 2d 9 ® g 15 010 BC548 10 .,.8 .,.. o* + 9 I a 16 680k 390U 390\l 390\l 390\l ~1 S1 IC6 4017 9 013 BC548 E 14 0.1+ FND500 + 2d B "'""& SPEAKER.,. EOC VIEWED FROM BELOW 13 15 10k g 10 B .,. .., FRUIT MACHINE JANUARY 1991 23 PARTS LIST 1 wooden case (see text) 1 PC board, code SC08101911, 138 x 102mm, 1 lever assembly (see text) 1 microswitch (S1) 1 50mm an loudspeaker 1 2.1 mm DC socket 1 12V DC plugpack and matching DC plug 30 Molex pins Semiconductors 3 FND500 common cathode red LED displays 3 555 timers (IC1, IC3, IC5) 3 4017 decade counters (IC2, IC4, IC6) 9 BC548 NPN transistors (02, 03,05,07,08,010,012, 013,015) 6 BC557 PNP transistors (01, 04,06,09,011,014) 1 1N4002 silicon diode (D1) 21 1N914, 1N4148 silicon diodes (D2-D22) Capacitors 1 100µF 16VW electrolytic 3 1µF 16VW electrolytic 3 0.1 µF 160VW metallised polyester (greencap) Resistors (0.25W, 5%) 3 3.3MQ 15 10kQ 1 680kQ 15 3900 1 470kQ 1 470 4270kn 24 SILICON CHIP involving Ql, ICl, IC2 and an FND500 7-segment LED display. In essence, this circuit consists of a free-running oscillator (ICl), a decade counter and a diode decoding net'l(Vork to drive the 7-segment display. Let's look at the decade counder, IC2, first. It is a 4017 with 10 individual outputs, which go high successively. In our circuit, we are only using six of these outputs and these are connected to a decoding network consisting of seven diodes, D2-D8. These drive four transistors, Q2-Q5, which then drive the a-g segments of the display. Display decoding Let's see how the transistors and diodes produce the various displays. For example, to give the display "L", segments 'e', 'f' and 'd' need to be lit. Segments 'e' and 'f' are connected together and permanently connectec:l to the positive supply via a 3900 re'~ sistor. So the 'e' and 'f' segments are on all the time. For the 'd' segment to be lit, Q4 Below left: push all the parts down onto the PC board as far as they will go before soldering their leads. The three FND500 displays are mounted on Molex strips, as described in the text. After assembly, the completed board is secured by two screws to wooden blocks in the back of the case, as shown in the view below right. must turn on and so its base must be pulled low by pin 9 of IC2. This pin will be low for 9/loths of the time, so the 'd' segment will be on for the same amount of time. This makes sense because the 'd' segment needs to be lit to produce the "C", "L" and "O" displays. The 'a' segment is driven by QZ, an NPN transistor. For QZ to turn on, either pin 1, 3, 4, 6, 7 or 9 of ICZ needs to be high and so cause the relevant diode(s) (DZ-D8) to conduct. So the 'a' segment will be on for 6/loths of the time. Again, this makes sense because the 'a' segment needs to be lit to produce the "A", "O' and "C" displays. Now consider the 'b' and 'c' segments. These are connected together and driven by Q3, another NPN transistor. Q3 is turned on whenever pins 6, 7 or 9 are high. The 'b' and 'c' segments need to be lit to produce the "A" and "O" displays. For its part, the 'g' segment is driven by Q5 and it can only turn on when pin 9 of ICl is high. From the above , we can see that to produce the "A" display, we need all segments on except the 'd'. So to get an "A" display, Q4 must be off (segment 'd' unlit) and QZ, Q3 and Q5 must all be on. This condition only occurs when pin 9 of ICZ is high. Get the picture? Similarly, to obtain an "O" display, all segments except 'g' must be lit. For this to happen, Q4 must be off and the three TO S1 three separate circuits. By now, you will probably have noted that the three separate circuits are very similar. There are in fact, only two points of difference. One involves the resistors associated with the lµF capacitor. In the case ofQl, there are 3.3MQ and 270kQ bias resistors. In the case of Q6, the resistors are 3.3Q and 470kQ, while for Ql 1 the resistors are 3.3MQ and 680kQ. These larger resistor values mean that Q6 stays on for a little longer than Ql, while Ql 1 stays on for a little longer than Q6. In practice, this means that the LED display associated with Ql stops first, followed by the display for Q6 and then the display for Ql 1. This simulates the action of a real poker machine whereby the reels come to a stop in succession. Noise source SPEAKER Fig.2: check that all parts are correctly oriented when installing them on the PC board, especially the transistors. Also, be sure to use the correct transistor type at each location. When mounting the FND500 displays, make sure that the decimal point is at lower right. other transistors on. This condition only occurs when pin 6 or pin 7 of IC2 is high. So we can already see that there is a "time bias" in the circuit and that the "O" display will be lit-for somewhat less time than the "C" display and the "A" display will be on for the least amount of time. So far then , we have seen how IC2 and the following components produce the various letter displays. We now look at IC1 which functions as the clock for IC2 . IC1 is a 555 timer connected in astable mode. When Ql is turned fully on, IC1 will feed clock pulses into pin 14 of IC2 at a frequency of about 3Hz. The lever switch Ql is turned on whenever the Play switch Sl is closed. This pulls the base of Ql low via the 3.3MQ resistor and charges the associated lµF capacitor. When the Play switch is released, the lµF capacitor then keeps Ql turned on until it discharges via the base bias resistors. It is at this point that we need to talk about the differences between the The other differe nce in the three circuits is that IC5 , a 555 timer and clock source for IC6, drives a loudspeaker via a 47Q resistor and lO0µF capacitor to give some "action" sound - a stream of clicks of decreasing frequency as the circuit winds down. Power for the circuit comes from a standard 12V DC plugpack via diode Dl which provides protection against reverse polarity connection. Construction As noted above, the Fruit Machine is housed in a small wooden case and the circuit is installed on a PC board measuring 138 x 102mm and coded 08101911. As much as possible, the components on the board have been lined up in rows which tends to make assembly easier. All the ICs and diodes face in the same direction but the transistors do not, so some care will have tobe taken when installing them. RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 No Value 4-Band Code (5%) 5-Band Code (1%) 3 1 3.3MQ 680kQ 470kQ 270kQ 10kQ 390Q 47Q orange orange green gold blue grey yellow gold yellow violet yellow gold red violet yellow gold brown black orange gold orange white brown gold yellow violet black gold orange orange black yellow brown blue grey black orange brown yellow violet black orange brown red violet black orange brown brown black black red brown orange white black black brown yellow violet black gold brown 4 15 15 JA NUA RY 1991 25 The Play microswitch is activated by a screw which is secured to a brass rod handle via a bush. This view shows the switch in the open position. We would suggest that the PC board be assembled first and checked out for correct operation. After that, the wooden box can be made. The first step in assembling the board is to check that it has no defects such as undrilled holes, shorts between tracks or open circuits (breaks) in tracks. You can check the board against the pattern published with this article. When the handle is pulled, the brass rod rotates & the screw closes the microswitch. The spring then returns the handle to the rest position when it is released. You can then start by fitting all the diodes and the resistors. The full wiring diagram is shown in Fig.2. To make subsequent checking of your work easier, install the resistors so that their colour codes all run in the same direction. This done, install the three wire links and the six ICs, then insert the three 0.1µF capacitors and the four electrolytic capacitors, making sure that the latter are all in- stalled the right way around. Now the transistors can all be installed. Those for the displays all face in the same direction except the BC557 PNP types which face the other way. Lastly, the three LED displays can be installed. These are not directly soldered into circuit but are inserted into sockets made from Molex connector strip. You can buy this connector strip in long lengths. You just snap off the lengths you want, 5-pin in this case, solder them into the PC board and then snap off the top sections. When installing the three LED displays into their sockets, make sure you install them the correct way around. When upright, the decimal point for each display should be in its correct position. Note: the decimal point is not used in this circuit but you still have to put the dis- Fig.3: this is the full-size artwork for the PC board. You can use it to etch your own board or to check that the board you receive has been correctly etched. 26 SILICON CHIP 48 ◄ 40 Fig.4: this diagram shows the dimensions of the wooden case used to house the prototype. The front & back panels were made of Masonite, while the side panels & spacers were made of pine. I ~-i---- - -----,:_-_ iI I I r-- --~ I [ ] i I Cl - 2xWOOD SPACERS 12x12x40 I I I I C, "" I I I I I DIMENSIONS IN MILLIMETRES play in the right way otherwise it won't work. Now you ready to check the PC board for correct operation. If you want to, you can install a pushbutton switch temporarily on the board to function as a Play switch. You can also temporarily connect a speaker so that you can have sound. . Now apply power to the circuit. The three LED displays should light up and they should all give one of the designated letters; ie, A, 0, C or L. Our prototype powers up with three Ls. Now operate the Play switch and observe that all displays cycle and that they come to a stop in sequence, first the lefthand display, then the centre one and last, the righthand display. The speaker should also make a clicking noise which slows down and stops when the lefthand display comes to a stop. That being the case, you can set to and make a box for the unit. The prototype was made with sides of pine and the front and back panels of Ma-sonite. The front Masonite panel was glued in place while the rear panel is held on with a couple of woodscrews. The PC board is supported on a pair of woodspacers 12mm thick, immediately behind the front panel. The full details of the timber case are RCS Radio Pty Ltd is the only company which manufactures and sells every PCB E, front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. shown in the diagram of Fig.4. As far as the Play switch is concerned, you have two options. You can take the easy way out and just have a pushbutton switch mounted on the printed board and protruding through the front panel; or you can do it with a a little more style and make a lever switch. The lever on the prototype was made from 5mm diameter brass rod bent at rightangles and passed through both sides of the box. A bush was mounted on the horizontal shaft and arranged to trip a microswitch mounted on the side of the case (see photos). The knob on the lever was a plastic ball 21mm in diameter and drilled to be a tight fit on the rod. The 2.1mm DC socket was mounted on the back panel. The front panel was made quite simply. A layer of red Cellophane was placed over the Masonite panel and held in place with adhesive tape. Then a photostat copy of the front panel artwork was coloured in (yep, with colouring pencils) and glued over the panel. The whole lot was then given a protective coating with a clear layer of Contact covering (simple, but effective). SC JANUARY 1991 27