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ABSTRACT
STREET LIGHTNING USING SOLAR ENERGY has been purposely designed to make the efficient use of energy resources. It enables the views on using conventional resources. Operator to monitor data or processes distributed among various remote sites. Various sensors such as temperature sensor, pressure sensor, flow sensor etc. have been used.
It consists of two ends- The transmitting end & The receiving end.
TRANSMITTING END - The remote end from where the data is transmitted.
The temperature, pressure, flow or any other physical quantities are sensed by
the respective sensors located at different sites. By microcontroller programming
the switch is enabled and hence the sensor corresponding to the control line of the
switch is selected. The analog data from sensors is converted into digital by using
ADC. The digital data is passed onto the microcontroller, which displays the data
on the LCD. The digital data is then sent to the DTMF generator, which converts
the digital data into analog data and transmit over the transmission lines.
RECEIVING END – The industry end where the data is received.
At the receiving end the data in analog form is converted into digital form by
the DTMF receiver. The DTMF receiver, receives four bits of data at a time and
transmit them to the microcontroller, which displays the data on the LCD at the
factory end.
INTRODUCTION
• Technology overview
• History
TECHNOLOGY OVERVIEW
DTMF- DUAL TONE MULTI FREQUENCY
Dual-tone multi-frequency (DTMF) signaling is used for telecommunication signaling over analog telephone lines in the voice-frequency band between telephone handsets and other communications devices and the switching center.
Dual Tone Multi-Frequency, or DTMF, is a method for instructing a telephone switching system of the telephone number to be dialed, or to issue commands to switching systems or related telephony equipment.
The DTMF system uses eight different frequency signals transmitted in pairs to represent sixteen different numbers, symbols and letters - as detailed below.
Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air
Low group tones : 697, 770, 852, 941 Hz.
High group tones : 1209, 1336, 1477, 1633 Hz.
Frequency tolerance: f (1.5%+ 2 Hz)
Amplitude range : - 24dbm<a<+6dbm 600 ohm
Pause duration : 40ms or longer
Tone duration : 40ms or longer
A valid DTMF signal is the sum of two tones, one from a low group (697- 941Hz) and one from a high group (1209-1633Hz) with each group containing four individual tones
The DTMF coding scheme ensures that each signal contains one and only one component from each of the high and low groups. This significantly simplifies decoding because the composite DTMF signal may be separated with band pass filters, into its two single frequency components each of which may be handled individually. As a result DTMF coding has proven to provide a flexible signaling scheme of excellent reliability, hence motivating innovative and competitive decoder design.
DTMF was originally decoded by tuned filter banks. Late in the 20th century most were replaced with digital signal processors. DTMF can be decoded using the Goertzel algorithm
Inside The DTMF Decoder
The MT8870 is a state of the art single chip DTMF receiver incorporating switched capacitor filter technology and an advanced digital counting/averaging algorithm for period measurement. The block diagram (Fig. 5-4) illustrates the internal workings of this device.
To aid design flexibility, the DTMF input signal is first buffered by an input op amp, which allows adjustment of gain and choice of input configuration. The input stage is followed by a low pass continuous RC active filter, which performs an anti-aliasing function. For a dial tone at 350 and 440Hz is then rejected by a third order switched capacitor notch filter. The signal, still in its composite form, is then split into its individual high and low frequency components by two sixth order switched capacitor and pass filters. Each component tone is then smoothed by an output filter and squared up by a hard limiting comparator.
The two resulting rectangular waves are applied to digital circuitry where a counting algorithm measures and averages their periods. An accurate reference clock is derived from an inexpensive external 3.58MHz colourburst crystal.The timing diagram (Fig. 5-5)

illustrates the sequence of events, which follow digital detection of a DTMF tone pair. Upon recognition of a valid frequency from each tone group the Early Steering (ESt) output is raised. The time required to detect the presence of two valid tones, tDP, is a function of the decode algorithm, the tone frequency and the previous state of the decode logic. ESt indicates that two tones of proper frequency have been detected and initiates an RC timing circuit. If both tones are present for the minimum guard time, tGTP, which is determined by the external RC network, the DTMF signal is decoded and the resulting data is latched in the output register. The Delayed Steering (StD) output is raised and indicates that new data is available. The time required to receive a valid DTMF signal, tREC, is equal to the sum of tDP and tGTP. The task of DTMF receiver is to detect the presence of a valid tone pair on a telephone line or other transmission medium. The presence of a valid tone pairs indicates a signal digit.
How DTMF principle is implemented in this system?
As we know that corresponding to each character (from 0-D) a set of DTMF frequencies are sent .So in total we have 16 pairs of DTMF tones .In our system we are combining two of these tone pairs corresponding to each character of the message. Therefore at the sender end the message is encoded and at the receiver end the message is decoded.
TOOLS
The following tools have been used to develop this system:
Hardware Tools
1.) Cathode Ray Oscilloscope (CRO)
This tool is used for the testing purpose. This is used to debug the faults at various test points by observing the waveforms.
2.) Multimeter
This is a multipurpose tool used to check voltages and currents at the test points. Is also used for checking the connectivity between two points on the circuit. Used to measure resistances, to find polarity of transistor and diodes. Also is used to find the hfe of the transistors.
3.) Microcontroller programmer:
In-System Programming (ISP) is a process whereby a blank device mounted to a circuit board can be programmed with the end-user code without the need to remove the device from the circuit board. Also, a previously programmed device can be erased and reprogrammed without removal from the circuit board. In order to perform ISP operations the microcontroller is powered up in a special “ISP mode”. ISP mode allows the microcontroller to communicate with an external host device through the serial port, Such as a PC or terminal. The microcontroller receives commands and data from the host,
erases and reprograms code memory, etc. Once the ISP operations have been completed the device is reconfigured so that it will operate normally the next time it is either Reset or power removed and reapplied.