This
spy bug circuit will help you to listen to a conversation without being
noticed or simply when you want to spy on a person. The circuit is
constructed using a Mic, an Amplifier and a Speaker. The device can be
wired or wireless depending on the comfort of your design. The device is
built around an OpAmp IC741. It consists of a NPN transistor Q1(2N222)
and a PNP transistor Q2(2N2907) connected in Push-Pull configuration.
Working:
This circuit can be divided into three sections for better understanding. First part is the Receiver, which
is built using an Electric Microphone (Mic) and a Resistor R1. The
microphone converts the sound into electrical signal and R1 adjusts the
sensitivity of the Mic. The resistor R2 serves as a volume control and
capacitor C1 is used to remove the dc component of the signal. Next comes
the pre-amplifier stage which is built using the OpAmp IC741. The IC is
wired as an Inverting amplifier and hence the input signal is passed
through the inverting terminal of the IC. The positive terminal or the
non-inverting terminal is biased using the voltage divider R3 and R4.
The resistor R5 is used to provide the negative feedback to the Opamp
which in turn controls the gain of the Opamp. The final
stage comes to the amplifier built using the transistors Q1 (2N222) and
Q2 (2N2907). These transistors are connected in Push Pull configuration
which implies that one of the transistors amplifies the positive half
cycle of the input and the other amplifies the negative half cycle.
Collectively, we obtain an amplified 180 degree out of phase signal from
the amplifier. The signal is then passed through the capacitor C2 to
filter out any dc components and then finally to the Speaker.
A Chasis for your BOT ( You can build it yourself )
Two DC Motors along with Tires
L293D Motor Driver
Caster Wheel
Infrared Sensors ( Transmitter and Receiver - 5 each )
5K Potentiometers for PCB
9V Battery for Power Supply
Bluetooth Module for Wireless Remote Control
Analog Joystick or Push Buttons for Wired Remote Control
Male and Female Connectors ( 10 each )
Description:
Designing the Body:
Before configuring any Hardware or Programming, you should take care of the chasis (body of the robot) that you are going to use. Once you get ready with your chasis, connect the two motors adjacently on two sides of the chasis and wind them with the help of zip ties or whatever you are comfortable with (make sure that the motor is tied tightly enough with the chasis). After that, connect a caster wheel at the front end of the chasis to make a free wheel, so that your bot can move sideways freely with the help of just two motors.
After you get the design of your bot ready, here comes the critical and the most important part. To build a line following robot with manual control, you have to deal with two parts basically: The Automated Part and The Manual Part.
The Automated Part:
To begin the automated part, you must first design the sensor of your robot. You can build the sensor yourself by buying the infrared sensors and the potentiometers or you can easily get a "digital sensor" from the market which will work even better with your project. If you want to learn to build a sensor board yourself with the help of infrared sensors, click here.
Once you get done with your sensor board, you need to check whether it does work with the design of your arena or not. For this, you need to have some knowledge about serial monitoring. Serial Monitoring helps you to check whether your sensor is working correctly or not. So, after you get done with your sensor board, you move on to the next part, i.e. the manual part. The Manual Part:
You can control a robot manually with the help of a remote control, which can be wired or wireless. Making the manual part of the robot is not as complicated as the automated part. So, you can handle this with more comfort. Wired: If you want to make a wired remote control for your robot which can be a cheaper option, then you can deal with analog joysticks or the push buttons. Another thing that you can try is a movable potentiometer which can work like a joystick. Once you build your remote with any of the above components, you can connect the wires to the arduino digital pins directly. You need to make sure that you send either a high voltage signal or a low voltage signal to command your bot accordingly. For example: If you are using 4 push buttons, then each button should send a '1' (HIGH) signal to an arduino digital pin so that you can process the particular signal to perform the operation on your robot. Wireless: Making a wireless remote control for your bot is comparatively easier, but a little expensive. All you need is a bluetooth module and a smartphone. You connect the bluetooth module to an analog pin of the arduino and serial monitor the input from your smartphone to the arduino, whenever you press any button on the app of your smartphone. Then, by analyzing the different values received by the module from your smartphone by pressing different buttons on your phone, you write a program to perform the respective task using the if...else conditions.
How to switch between the Automatic and the Manual part? Most people get confused when it comes to switching between the automatic and the manual part in their program. Well, it's quite simple with a technique that I generally use. You can also use the Interrupt technique to switch your robot, but I prefer using a separate digital pin to do that. Assign a separate digital pin and connect a button to the pin if you are using a wired remote. As soon as you give a high signal to the pin, make your program runs the automatic part. You can also use a separate pin for the manual part which is activated when you give a high voltage to that pin. This might get confusing to you, but you will eventually get to the point that I'm trying to explain, once you get done with the programming part that we discussed earlier. For the wireless remote, it is quite simple. You don't even need to use a different pin for this purpose. Assume a button in your phone application that you want to use to change the robot from being autonomous to a manually controlled one. Check its value using the serial monitor and assign it in your program for doing the exact operation that you want when the button is pressed. Do the exact same with another similar button when you want to switch from manual to the automatic part. That is it. Well, I must say, it's easier to read a blog about building an automatic robot, but it is a challenging task to build it on your own. You will eventually get tangled with a lot of problems, once you get going with your project. But remember one thing, "Every problem has different solutions to it". I wish you luck to make your project a success. Keep sharing. Keep building. Thank You.
An electronic eye is a simple circuit which operates the
buzzer when a shadow falls on it. Initially
a 9V battery is connected to the diode D1 which is in forward biased
condition. This diode protects the circuit form negative voltages by allowing
the current to flow in only one direction. A regulator IC 7805 regulates the
voltage to 5V at the output. The two capacitors used before and after the
regulators eliminate the ripple voltage so a constant voltage can be produced.
Light dependent resistors have resistance in mega ohms when
it is placed in dark producing logic high at the output and low resistance when
placed in light i.e. logic low at the output. This output is received by op-amp
which compares the two inputs and send output to the two transistors. The first transistor inverts
the input and the second transistor drives the buzzer. The buzzer starts
ringing when the logic is high and also the LED starts blinking.
FM transimission is done by the principle of audio pre amplification, modulation and then transmission. Here, we amplify the audio input signal taken from the Electret Microphone with the help of the transistor Q1, modulate it according to its frequency with the help of the inductor coil and finally we transmit it through the antenna connected to the inductor coil. This is just a simple model of FM transmitter and it works just up to a certain range (about 100-200 meters). Note: We should keep in mind that modulating transmission of a certain standard frequency is a breach of the law and it should not be practiced in real life. So, just build it as a learning project in a very small scale.
This system mainly works on a principle that “water conducts electricity”. The four wires which are dipped into the tank will indicate the different water levels. Based on the outputs of these wires, microcontroller displays water level on LCD as well as controls the motor.
Components Required:
At89c51 controller
At89c51 programming board.
16*2 LCD
5V Relay
Bc547 (NPN) transistors – 5
Resistors (1K) – 4
Resistor – 330 ohm
AC Motor
Pot – 10k
Programming cable
Connecting wires
Working:
The main heart of this project is AT89C51 microcontroller. The water level probes are connected to the P3.0, P3.1, P3.2, and P3.3 through the transistors. Port P2 connected to the data pins of LCD and control pins RS, RW and EN of LCD are connected to the P1.0, P1.1, and P1.2 respectively.
Initially when tank is empty, LCD will display the message EMPTY and motor runs automatically. When water level reaches to quarter level, now LCD displays QUARTER and still motor runs. For further levels, LCD displays the messages HALF and ¾ FULL.
When tank is full, LCD displays FULL and motor automatically stops. Again motor runs when tank is empty.
Algorithm:
First configure the controller pins P3.0, P3.1, P3.2 and P3.3 as inputs and P3.4 as output.
Now initialize the LCD.
Continuously check the water level input pins P3.0, P3.1, P3.2, and P3.3
If all the pins are low then display tank is empty on LCD and make P3.4 pin high to run the motor automatically.
High pulse on the pin P3.0 indicates quarter level, display the same thing on LCD.
If P3.1 is high then water level is half.
High pulse on P3.2 indicates 3/4th full of the tank.
If P3.3 is high then tank is full, now make P3.4 pin is low to turn off the motor automatically.
