This project is an electronic quiz buzzer that is affordable by the colleges and even individuals. This project is useful for a 4-team quiz contest, although it can be modified for more number of teams. This system is sensitive. The circuit can detect and record the first hit contestant among all the contestants that may appear to be simultaneous.
The circuit uses IC 555 and a few passive components that are readily available in the market.
This project causes lights to blink and flash to music from your TV, stereo, guitar and even your own voice. The device presented here needs no connection to the sound source, it picks up sound from its built in mic.
Components Required :-
C1 1 22uf 250V Electrolytic Capacitor
C2 1 22uf 250V Electrolytic Capacitor
C3 1 0.1uf Disc Capacitor
C4 1 0.01uf Disc Capacitor
C5 1 0.0047uf Disc Capacitor
R1 1 47K 1/2 W Resistor
R2, R4 2 6.8K 1/2 W Resistor
R3, R5 2 1M 1/2 W Resistor
R6 1 3.3K 1/2 W Resistor
R7, R8, R9 3 1K 1/2 W Resistor
R10, R11, R12 3 10K Pot
D1 1 1N4004 Diode
Q1, Q2 2 2N3904 NPN Transistor 2N2222
Q3, Q4, Q5 3 106B1 SCR Teccor S2003LS1
T1 1 10K:600 Ohm Audio Transformer
S1 1 SPDT Switch
J1, J2, J3 3 AC Socket
MISC 1 AC Line Cord, Crystal Microphone, Case, Wire.
This is a mobile phone detector circuit that can detect the signals being used in the GSM at about 900 MHz. Since the signals are digitally encoded, it can detect only the signal activity, not the speech or the message contents. A headphone or a set of speakers can be used to hear the detected signals.
AT89C52 based Robo-Car (involves programming AT89C52, source code provided).
The robotic car or Robo Car employs the micro controller AT89C52 to detect obstacles and manipulate its direction as per the inputs from three infra-red sensors mounted atop of the car.
Description -
When the RoboCar is powered on, the micro-controller (IC4) fetches the code from its internal memory and sets its pin 10 high and pin 11 low. This signal is fed to pin 2 and pin 7 of IC3 (motor driver), which drives the DC motor in one direction. This enables the car to move forward. IC5 (NE555 timer) is wired as an astable multi-vibrator to generate a 38 KHz pulse. The 38 KHz pulses are amplified by transistor T1 to drive five IR LEDs. The IR sensors and LEDs are arranged in such a way that the output of the sensors is high where there is no obstacle near the car. But if there is any obstacle, the transmitted IR signals from the IR LED are reflected back from the obstacle that comes in the way. This makes the sensor output go low. This low output signal is fed to port 0 of the micro-controller. The output of sensor Q1 is connected to P0.0, Q2 to P0.1 and Q3 to port P0.2. As soon as the output of the left sensor Q1 is pulled low to P0.0=0, the controller alters the spin of the DC motor, makes port P3=0 and stops the DC motor, thereby stopping the car for a moment. Then it drives port 1 in such a way that the stepper motor is rotated to the right, and the front steering wheels are also turned right, while the car continues to move forward. After a few seconds, the controller drives the stepper motor in the reverse direction (turning it left), which brings the steering wheels to the straight position and moves the car forward. Similar is the case when an obstacle is detected at the right sensor Q2. In case there is an obstacle in the front, the centre sensor Q3 sends a low signal to port pin P0.2. This makes port P3=0 and the car stops. The steering wheels are turned left making port P3.0=0 and P3.1=1, which moves the car in backward direction with the steering still turned. After a few seconds, the DC motor is stopped by making port P3=0. The steering is set in the straight position and the car moves forward by making the port P3.0=1 and P3.1=0. Thus, when the port P3.0=0 and P3.1=1, the car moves in the reverse direction; when P3.0=1 and P3.0=0, the car moves in the forward direction and when P3.0=0 and P3.1=0, the car stops.
