Some application may use this circuit such as robot applications, body height measurement, blind shoes, etc.

How the circuit works:

The transmitter emits an ultrasonic signal (40kHz). The 555 timer chip of the transmitter provides the driving 40kHz signal. Every time the reset pin (pin4) of the 555 timer goes high, a resulting signal of 40kHz on pin 3 is used to drive the ultrasonic transducer. Then, the receiver simply listens for the return echo after it bounces off an object. The small echo signal, when detected, is amplified 1000 times using a standard operational amplifier (LM741 op-amp). The signal is then fed into a tone decoder (LM567) set to lock onto a 40kHz signal. The output of the tone decoder is HIGH when no echo is heard and swings LOW when an echo is detected. The output from the tone decoder can now be fed into a microcontroller or some other type of IC to determine when an echo was received. To help minimize false triggering, the output is fed into a voltage comparator set to trigger at the appropriate level. The LED at the output of the comparator acts as a visual indicator when an echo is detected (very useful when debugging). The typical range of this system is from a few inches to 5-6 feet, depending on the quality of the components, shielding, and most important, tuning.

Detailed explanation about this ultrasonic distance detector circuit: visit this page

Or download this documentation:

Kam Leang Robotics - Sonar Ranging System

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This is the circuit diagram of white line follower toy. The actuator of the toy is the DC motor. This circuit can be used for?a toy car to follow a white?line, this circuit also known as very simple robot: “line follower without microcontroller”. The motor is either a?3v type with gearing to?steer the car or a rotary?actuator or a servo motor.

How the circuit work..?

When equal light is detected by the photo resistors the voltage on the base of the first transistor will be mid rail and the circuit is adjusted via the 2k2 potensiometer so the motor does not receive any voltage. When one of the LDR’s receives more (or less) light, the motor is turned on / activated. And the same thing will be happen when the other LDR receives less or more light.

You can see the below video as the result of this circuit project:

About Arduino UNO:
The Arduino Uno is really a microcontroller board based on the ATmega328. It has 14 digital input/output pins (of which 6 may be employed as PWM outputs), 6 analog inputs, a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, along with a reset button. It contains every little thing needed to support the microcontroller; just connect it to a laptop or computer having a USB cable or power it with a AC-to-DC adapter or battery to obtain began.

The UNO differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it functions the Atmega8U2 programmed as a USB-to-serial converter.

“UNO” means one in Italian and is named to mark the upcoming release of Arduino 1.0. The Uno and version 1.0 is going to be the reference versions of Arduno, moving forward. The Uno will be the latest in a series of USB Arduino boards, along with the reference model for the Arduino platform; for a comparison with previous versions, see the index of Arduino boards.

Arduino UNO schematic download area

Download Arduino UNO: Arduino UNO schematic | Mirror File
Download EAGLE design: Arduino UNO schematic | Mirror File
Eagle files contain Arduino UNO schematic and board design

Tone Detector diagram 1

Tone Detector diagram 2

Tone Detector diagram 3

Tone Detector diagram 4

Tone Detector diagram 5

Circuit source: Sound activated switch for robot

The ATmega8535 line follower robot uses 8 pieces of proximity sensor module. The sensor module use photodioda for detecting the reflection of light from the line/floor.

Proximity / Line Detector circuit:

ATmega8535 is a low cost and great microcontroller for your robot. This microcontroller is very easy to use, very easy to find, very easy to program. In this tutorial, we used C programming language.

Microcontroller ATmega8535 circuit:

The motor driver L298 able to control the motor with current output up to 2A for single DC motor. For double DC motors, there should be up to 1A for each output channel. This motor driver is very good for small and medium DC motor. L298 is great motor driver for small and medium size or robot such as line follower robot and fire fighter robot.

Motor Driver circuit with L298:

Download the complete ATmega8535 line follower robot tutorial which contains schematic diagram, robot design and source code in PDF version (Indonesian language):

Line Tracker Robot AVR ATmega8535

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IR sensor schematic diagram:

The robot uses IR sensors to sense the line, an array of 8 IR LEDs (Tx) and sensors (Rx), facing the ground has been used in this setup. The output of the sensors is an analog signal which depends on the amount of light reflected back, this analog signal is given to the comparator to produce 0s and 1s which are then fed to the uC

Mainboard (microcontroller + DC motor driver schematic diagram):

The L298 Motor Driver has 4 inputs to control the motion of the motors and two enable inputs which are used for switching the motors on and off. To control the speed of the motors a PWM waveform with variable duty cycle is applied to the enable pins. Rapidly switching the voltage between Vs and GND gives an effective voltage between Vs and GND whose value depends on the duty cycle of PWM. 100% duty cycle corresponds to voltage equal to Vs, 50 % corresponds to 0.5Vs and so on. The 1N4004 diodes are used to prevent back EMF of the motors from disturbing the remaining circuit. Many circuits use L293D for motor control, I chose L298 as it has current capacity of 2A per channel @ 45V compared to 0.6 A @ 36 V of a L293D. L293Dâ€s package is not suitable for attaching a good heat sink, practically you canâ€t use it above 16V without frying it. L298 on the other hand works happily at 16V without a heat sink, though it is always better to use one.

Download the document of ATmega16 line follower robot tutorial for complete tutorial including the working explanation of circuit and program, source code and schematic diagram.

Line Following Robot Tutorial ATMega16

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