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 NXP Semiconductors

  • Electronic Slot Machine

  • Created: Sep 16, 2014

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Most modern slot machines are designed to look and feel like the old mechanical models, but they work on a completely different principle. The outcome of each pull is actually controlled by a central computer inside the machine, not by the motion of the reels.. The slot machine`s realistic action is provided by seven ICs and three displays.

Two 555 CMOS timer ICs generate pulses. The first 555 timer is used to generate the clock pulses for the entire electronic slot machine. The pulses are coupled from the output (pin 3) to the clock inputs of the three 74HC4017 display-driver ICs. The displays are common-cathode 7-segment LED types. They are wired to display three different symbols, “L", “7", and “-", When all three displays show the same symbols, the HEF4023 (a 4023 triple 3-iriput NAND gate) decodes a winner and sends a signal to pin 5 of the HEF4001, this IC is a CMOS NOR gate and it turns on IC2, a second 555 timer IC. The 555 timer actually produces the winner tone on its output, pin 3. Transistors are used to drive the common-cathode displays. A LED is used to indicate the clock pulses, and a variable resistor is provided for each of these functions. Trimmer resistor P1 controls the overall clock rate, P2 controls the winner tone, and P3 controls the display brilliance.



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