Shooting Game Using IC555

This is a simple shooting game comprising of an infrared pulse emitter and receiver. There are 8 white leds and one green led which will light up periodically. The player has to shoot at the receiver when the green led lights up. This is a simple beginner’s project and can be used to make more complicated projects like “LASER TAG GAME”

COMPONENTS

· IC NE555 ( x3)

· IC CD4017B ( x1)

· IC CD4011B ( x1)

· IR module GPIU561 ( x1)

· Transistor BC547B ( x2)

· Red LED ( x8)

· Green LED ( x2)

· IR LED with reflector ( x1)

· Musical Buzzer

· 9V battery

· Switch (On/Off type)

· Switch (Push-to-ON type)

· Resistors:

(470k? x2) ; ( 22k? x2) ; ( 100k? x1) ; (150? x4) ; (180? x1) ; (10k? x1) ;

(4.7k? x1)

· Capacitors

(100µF,10V)x1 ; (10 µF,10V)x1 ; (10 µF, 16V)x1 ; (0.01 µF x3) ; (0.047 µF x1)

(0.0022 µF x1)

WORKING

This project involves 2 major circuits:

1. The infrared pulse generator:

Infrared gun (transmitter) for this electronic game is built around IC1 timer (NE555) wired as an astable multivibrator with a centre frequency of about 35 kHz.

As shown in the figure below, adding the resistor RB and connecting the trigger input to the threshold input causes the timer to self-trigger and run as a multivibrator. The capacitor C charges through RA and RB and then discharges through RB only. Therefore the duty cycle is controlled by the values of RA and RB.

Charge and discharge times (and, therefore, frequency and duty cycle) are independent of the supply voltage.

The figure below shows the typcal waveforms generated during astable operation. The output high level duration tH and low level duration tL can be calculated as follows:

tH = 0.693 (RA + RB) C

tL = 0.693 (RB) C

From this we get,

Period = tH + tL = 0.693 (RA + 2RB) C

Frequency = 1.44/(C (RA + 2RB))

From the circuit diagram, it can be observed that in the case of this particular pulse generator, the frequency is determined by the components R1, R2 and C2.

Inputs 2 and 6 have been connected together causing the timer to self trigger and run as an astable multivibrator. Pin 5 is used to control the trigger and threshold levels.

The output (a square pulse) is obtained from pin number 3 on the IC.

In this case, RA = 10k?, RB = 4.7k? and C = 0.0022?F. Thus the pulse frequency for these particular values is found to be 33.7 kHz – which is close to our chosen frequency of 35 kHz.

The duty cycle is found to be 0.242 (using the above formula).

2. The receiver circuit:

The receiver circuit has 3 main ICs – 2 NE555s (one wired as an astable multivibrator and the other for monostable operation) and 1 CD4017B (decade counter).

For monostable operation, any of these timers can be connected as shown in the figure below. If the output is low, application of a negative-going pulse to the trigger (TRIG) sets the flip-flop (Q goes low), drives the output high, and turns off Q1. Capacitor C then is charged through RA until the voltage across the capacitor reaches the threshold voltage of the threshold (THRES) input. If TRIG has returned to a high level, the output of the threshold comparator resets the flip-flop (Q goes high), drives the output low, and discharges C through Q1.

Monostable operation is initiated when TRIG voltage falls below the trigger threshold. Applying a falling trigger pulse to the RESET and TRIG simultaneously discharges C and reinitiates the cycle, commencing on the rising edge of the reset pulse.

Receiver Circuit

IC 2 (see circuit diagram below) is used for monostable operation. When the IR module receives an infrared pulse from the pulse generator, its output goes low. The resulting falling edge to the input (pin 2) of IC 2 triggers the IC and causes its output (at pin 3) to go high.

The other main IC in this circuit is the CD4017B decade counter. This is a 5 stage divide-by-10 Johnson counter with 10 decoded output bits and a carryout bit.

This counter is cleared to its zero count by a logical “1” on its reset line. This counter advances on the rising edge of the clock signal when the clock enable signal is in the logical “0” state.

The 10 decoded outputs are normally in the logical “0” state and go to the logical “1” state only in their respective time slots. Each decoded output remains high for a full clock cycle. The carry out signal completes a full cycle for every 10 clock input cycles and is used as a ripple carry signal to any succeeding stages.

When power switch S2 in the receiver is turned on, the astable multivibrator wired around IC3 (NE555) generates clock pulses which are fed to clock input (pin 14) of the decade counter IC4 (CD4017B).

This IC has ten outputs, and each one goes high sequentially, on the rising edge of successive clock pulses. As a result, the LEDs connected to the output appear to light up one after the other rapidly. You would notice that only nine outputs are used for driving LEDs. The tenth output (Q9) at pin 11 is connected to reset pin 15.

After an infrared pulse is received and ICs 2 and 3 (see circuit diagram) are triggered, resulting in clock enable (CE) pin 13 of IC4 to go high (normally held at low potential via resistor R8) and it starts counting. When the mono pulse ends and if the last hit LED happens to be the target LED then both inputs of the NAND gate N1 become high. As a result, the output of gate N2 also goes high. This in turn switched on the transisitor T2; thereby the ‘HIT’ LED lights up and the buzzer also sounds. At the end of the mono pulse period (which is about 5 seconds), decided by resistor R5 and capacitor C5, the monostable IC2 is again ready to receive another trigger pulse.

EXTENSION: These circuits can be modified to make “LASER TAG GAME”

Circuit Diagram

Receiver Circuit

(Tab 1)

IR PULSE GENERATOR

(Tab2)