An Electronic Game
Video games are very popular in urban area, even though video game equipment are very exclusive and expensive. The constructional details of an electronic shooting game are described here. It employs a minimum number of low-cost and easily available components, and has all the actual functions of electronic games. In place of video screen, this project uses an LED display.
Theme of the game
Shooting down a fast moving object in the sky is not easy. Here a number of military aeroplanes appear at different positions for very short durations. All the aircraft are green except one which is red. This one is considered to be the enemy’s bomber. The player has to immobilise this particular plane with the help of a pushbutton switch, which is supposed to be the trigger of a gun. If the aim and timing is accurate, the red plane remains on the screen while other planes fade away. The player thus wins the game.
How to play
First switch on the gadget. Set the chance indicator to zero by pressing reset switch SI. Then press STAR!’ switch S3. The LEDs (planes) start blinking, emulating the zigzag movement of planes. Press SHOOT switch S2 to hit the target. Each shot is accompanied by an actual gun sound and one of the LEDs (planes) stays on the screen indicating that it has been shot. Press the START switch to animate the display again.
The player gets eight chances for shooting. The number of chances availed is indicated by LEDs. On ninth attempt the whole circuit becomes invalid and a long tone is sounded to indicate that the game is over and it is time for cease fire.
IC4 (MN4017) along with the LEDs connected to its outputs functions as a sequential running light. IC3 is wired as a clock pulse generator. The input pin 14 of IC4 is connected to the output of IC3. IC MN4017 counts the clock pulses and drives the LEDs.
The reset pin 4 of IC3 is connected to the output of IC2 timer, which is wired as a bistable latch. By pressing S3, the voltage at trigger pin of IC2 is brought below 2/3 Vcc. As a result, the output goes high and remains in that stage until the voltage at threshold pin 6 of IC2 goes above 2/3 Vcc by pressing S2 (SHOOT). This brings the output of IC2 to low level and sets the functions of IC3 as well as IC4.
The audio oscillator wired around IC5 produces the gun sound effect. The positive voltage obtained through S2 is fed to the timing capacitor C2 through D2, R7, R9 and RIO. The charging and discharging of capacitor Cl produces a decay effect to emulate the actual gun sound. D2 checks the charge of Cl affecting threshold pin 6 of IC2.
IC1 MN4017 is also a decade counter. Its input pin 14 is connected to the output of IC2. Each time the output of IC2 goes high, IC1 counts one and the corresponding LED glows. When power is applied to the circuit through S4, the Q0 output of IC1 goes high to indicate chance number zero. If it is not so, it may be brought to zero by pressing reset switch (S5/S1). Each time the start switch is pressed, the chance counter LEDs advance one step.
The Q10 output (pin 11) of IC1 is connected to the base of transistor T1 through resistor R4. On the ninth attempt of shooting, pin 11 goes high and the saturated transistor connects pin 4 of IC2 to ground which resets its output. The positive voltage present at pin 11 of IC1 is applied to the frequency-determining RC network of IC5 to produce a continuous tone instead of a gun sound.
The zigzag idea
As a common practice, the LEDs on the output pins of IC4 (MN4017) are expected to glow in a sequential order. But in this project they are positioned haphazardly to confuse the player. This is achieved by the following techniques.
1. The positions of LEDs on the display board are not kept in sequential order.
2. Some LEDs are connected in series to the same output so that the simultaneous illumination of two LEDs at different points confuses the player further.
Adjust preset VR1 to get a fast LED drive so that the player is not able to win the game easily. However, it seems that the effective resistance of VR1 should be below 22-kilohm. Fig. 1 gives details of the circuit.
The actual- size PCB pattern is given in Fig. 2.All the three NE555 timer ICs can be soldered directly on the PCB. Use sockets for CMOS ICs.
Plastic or laminated sheet may be used for the panel. To make the gadget more attractive, the display panel should be covered with glass or transparent plastic sheet, as seen in calculators. The rear of this glass should be painted dark to make it opaque, leaving aeroplane-shaped spaces as shown in Fig. 4. The LEDs should be correctly positioned just below these spaces. The switches should be placed at most convenient positions. Switch S5 is mainly intended for commercial use of the project. It should not be under the control of player.
The miniature form of the electronic game described here can be modified to a commercial one by replacing the LEDs with AC mains lamps and SCR/triac circuits for a larger display. This modified model may be used for gambling in exhibitions and fairs.