In today’s world it is quite often to emerge from one technology to another. In recent years RF (radio frequency) technology is in used for majority of applications. But due to the development of telecommunications a technology called DTMF has been evolved.
Mobiles are easy way of communication and they are easy to control without bothering the range of coverage area and frequency.
What is DTMF?
As the name implies it generates two multiple frequencies, the type of frequency to be generated depends upon the DTMF generator. DTMF stands for dual tone multi frequency and it is the registered trade mark of AT&T (Telecommunication Company in U.S.A). It is also known as touch tone frequency. DTMF tones are generated by using DTMF generator, the keypad matrix of size 4×4 is used for generating two different frequencies. One of the DTMF tone (high frequency) is generated from one group i.e. rows and another frequency is of high time period is generated from the column group.
The robot is controlled by a cellular telephone that makes a call to the cell telephone appended to the robot. Over the span of a call, if any catch is squeezed, a tone relating to the catch squeezed is heard at the flip side of the call. This tone is called ‘Dual tone Multiple Frequency’ (DTMF) tone. The robot sees this DTMF tone with the mobile phone’s assistance stacked in the robot. The got tone is prepared by the microcontroller with the assistance of DTMF decoder HT9170. The decoder DTMF tone into its comparable twofold digit and this parallel number is sent to the microcontroller. The microcontroller is pre modified to take a choice for any given info and outputs it’s choice to engine drivers keeping in mind the end goal to drive the engines for forward or in reverse movement or a turn. The portable that makes a call to the cell mobile phone stacked in the robot goes about as a remote. So this basic mechanical task does not require the development of collector and transmitter units.
Ordinarily, remote controlled robots use RF circuits, which have the disadvantages of constrained working extent, restricted recurrence range and restricted control. Utilization of a cellular phone for mechanical control can beat these confinements. It gives the benefits of strong control, working extent as substantial as the scope zone of the administration supplier, no obstruction with different controllers and up to twelve controls. In spite of the fact that the appearance and capacities of robots differ inconceivably, all robots share the components of a mechanical, versatile structure under some type of control. The control of robot includes three particular stages: discernment, preparing and activity. For the most part, the preceptors are sensors mounted on the robot, handling is finished by the removable Atmega 8 microcontroller , and the undertaking (action)is performed utilizing DC motors.
How the Robot Operates?
The mobile at the user end acts as transmitter and the mobile attached to the robot acts as receiver. When a key is pressed a touch tone is generated. This tone is recognized by mobile on the robot side, based upon the instructions of the user the robot moves backwards, forward, left and right by using the actuators.
Working Block Diagram
When a key is pressed decoder at the robot side detects the touch tone and decodes the analog frequency to digital binary output. The corresponding binary output is used as the control for moving the robot in desired direction say forward, backward, left and right.
The mostly used decoder for electronic circuits is Motorola MT 8870 receiver IC but in this project we are using DTMF decoder HT9170.
L293D Motor Driver
For moving the robot in either direction we need to drive the motor. But it is not possible to control a motor with one IC like ULN 2003, and here comes the advantage with L293D. It is a special IC of 16 pin designed to control the motor in both directions simultaneously.
How it works
L293D works on the principle of dual H-bridge concept. In this IC 2 H-bridges are encapsulated so that it can drive two dc motors with ease. This IC is well suited for robotic applications.
The designers had imagined phones being utilized to get to PCs, and studied various organizations to see what they would requirement for this part. This prompted the number’s expansion sign (#, in some cases called “octothorpe” in this setting) and reference mark or “star” (*) keys and additionally a gathering of keys for menu choice: A, B, C and D. At last, the lettered keys were dropped from most telephones, and it was numerous years prior to these keys turned out to be generally utilized for vertical administration codes, for example, *67 in the United States and Canada to stifle guest ID.
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