This is a simple shooter consisting of an infrared pulse emitter and receiver. There are 8 white LEDs and a green LED that light up periodically. The player must shoot the receiver when the green LED lights up. This is a simple project for beginners and can be used to make more complicated projects like “LASER TAG GAME”
COMPONENTS
· CI NE555 (x3)
· IC CD4017B (x1)
· IC CD4011B (x1)
· GPIU561 IR Module (x1)
· BC547B Transistor (x2)
· Red LED (x8)
· Green LED (x2)
· Infrared LED with reflector (x1)
· Musical Bell
· 9V battery
· Switch (on/off type)
· Switch (push-to-ON type)
· Resistors :
(470 thousand? x2); (22k?x2); (100 thousand? x1); (150?x4); (180?x1); (10k?x1);
(4.7 thousand? 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 main circuits:
1. The infrared pulse generator:
The infrared weapon (transmitter) for this electronic game is built around the timer IC1 (NE555) connected as an astable multivibrator with a center frequency of about 35 kHz.
As shown in the figure below, adding the RB resistor and connecting the trigger input to the limit input makes the timer trigger automatically and works as a multivibrator. Capacitor C charges through RA and RB and then discharges only through RB. 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 typical 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 seen that in the case of this specific pulse generator, the frequency is determined by components R1, R2 and C2.
Inputs 2 and 6 were connected together, causing the timer to fire automatically and function as an astable multivibrator. Pin 5 is used to control trigger and limit levels.
The output (a square pulse) is taken at pin number 3 of the IC.
In this case, RA = 10k?, RB = 4.7k? and C = 0.0022?F. Therefore, the pulse frequency for these specific values is 33.7 kHz – which is close to the chosen frequency of 35 kHz.
The duty cycle is 0.242 (using the formula above).
2. The receiver circuit:
The receiver circuit has 3 main ICs – 2 NE555s (one connected 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, applying a negative pulse to the trigger (TRIG) sets the flip-flop (Q goes low), increases the output, and turns off Q1. Capacitor C is then charged through RA until the voltage across the capacitor reaches the threshold input voltage (THRES). If TRIG has returned to a high level, the limit comparator output resets the flip-flop (Q goes high), drives the output low, and dumps C to Q1.
Monostable operation begins when the TRIG voltage drops below the trigger threshold. Applying a falling trigger pulse to RESET and TRIG simultaneously discharges C and restarts the cycle, starting at 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 becomes 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 divided-by-10 Johnson counter with 10 decoded output bits and one carryout bit.
This counter is reset 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 logic “0” state.
The 10 decoded outputs are normally in the logic “0” state and switch to the logic “1” state only in their respective time intervals. Each decoded output remains high for a full clock cycle. The run signal completes one full cycle for every 10 clock input cycles and is used as a ripple carry signal for any subsequent stages.
When the power switch S2 on the receiver is turned on, the astable multivibrator connected to IC3 (NE555) generates clock pulses that are fed into the clock input (pin 14) of decade counter IC4 (CD4017B).
This IC has ten outputs, and each 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 quickly. You would notice that only nine outputs are used to drive LEDs. The tenth output (Q9) on 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 the clock enable (CE) pin 13 of IC4 to go high (normally held at low potential via resistor R8 ) and he starts counting. When the mono pulse ends and if the last LED hit is the target LED, both NAND gate N1 inputs become high. As a result, the output of port N2 also increases. This, in turn, turned on transistor T2; thus, 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
(Tab 2)
Circuit diagrams
| circuit diagram_0 |  |
| IR pulse generator |  |
