Experimental Validation of DTMF Decoder Electronic Circuit to be Used for Remote Controlling of an Agricultural Pump System

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1 Experimental Validation of DTMF Decoder Electronic Circuit to be Used for Remote Controlling of an Agricultural Pump System Hussain A. Attia, Beza Negash Getu, Nasser Hamad Department of Electronics and Communications Engineering American University of Ras Al Khaimah Ras Al Khaimah, UAE ABSTRACT This work investigates the implementation and experimental analysis of practical DTMF decoder electronic circuit that can be used for remote controlling of agricultural pump system or other applications. A DTMF tone command sent from a transmitting fixed or mobile phone station will be decoded by the electronic circuit at the receiving phone station and accordingly the command signal will be interpreted and then be used to SWITCH ON/OFF selected or several motors that are used to pump water for agricultural fields. The paper presents the experimental work and analysis results of the different stages of the design confirming our previous simulation work using the NI-Multism program. The results of the simulation and the experimental work show that the electronic design is capable of controlling the switching state of the pumping motors. KEYWORDS DTMF, Touch-Tone, Remote Control, Op-Amps, Bandpass Filters 1 INTRODUCTION In recent years, there is a widespread use of telephone signals of fixed phone, mobile phone and wireless devices for remote controlling applications such as house and property security surveillance system, theft control and monitoring systems, remote motor speed control, remote real-time industrial process control & monitoring, remote door locking system, remote controlling of electrical apparatus in offices and homes, remote operation of robotic systems, remote vehicular security systems, remote switching systems and other relevant applications, [1], [2]. More specifically, the use of Dual Tone Multi-Frequency (DTMF) technique is becoming predominant in various remote controlling applications [3]-[7]. In [8], the use of DTMF signaling for remote controlling of agricultural pumps was studied in detail. A complete electronic design and MULTISIM simulation was presented. The results of different stages of the simulation showed the capability of the system for controlling the switching states of the water pumping motors used for the irrigation at a remotely located agricultural site. A farmer who controls the irrigation of an agriculture site remotely will press the keypad of the telephone handset and can switch on or off water pumps located at the different locations of the site. Depending on the requirement, one or several pumps that are available in the agricultural site can be switched on/off at the same time or at different times. A DTMF decoder and controlling logic circuit are designed to control high power pumps by issuing commands encoded as audio DTMF signals. The DTMF decoder and controlling circuit receives those remote commands and controls the switching states of the connected motor pump system. 2 SYSTEM MODEL From the purpose of the proposed system, it is obvious that we need a transmitter phone (fixed or mobile), a receiver phone (fixed or mobile), DTMF decoder and Logic Controller, which could be a microcontroller and a motor drive circuit used for switching the motor pumps. Figure 1 shows the general block diagram of the receiving end showing the different parts of the system. At the transmitter, the farmer or any other assigned user will send the DTMF control signal by first dialing the receiver mobile or fixed phone. After the answering mode is completed, the user will send an appropriate DTMF tone command to switch on/off one or several of the motor pumps. The received DTMF tone ISBN: SDIWC 52

2 command will be decoded by an appropriate DTMF decoder circuit. In this work, we designed an analogue filter to decode the DTMF tones using easily available passive and active electronic components. After the decoding of the tones, a logic controller is designed to identify the exact transmitted phone digit corresponding to the transmitted DTMF tone. A motor driving circuit corresponding to the transmitted digit will be enabled and the driving circuit will switch on/off one or several of the motor pumps according to the design specifications. In this work, we continue the work presented in [8] and conform the MULTISIM theoretical simulation results with the experimental results as presented in the subsequent section of this paper. the signal in (1) can be determined if we sample the signal and replace t with t = nts where the sampling time Ts is the reciprocal of the sampling frequency Fs. Fs is often taken as 8000 Hz, which is the sampling frequency of voice signals Hz 1336 Hz 177 Hz 1633 Hz 697 Hz A 770 Hz 5 6 B 852 Hz C 91 Hz * 0 # D Receiver phone DTMF Decoder Motor drive circuit (Relay) Logic controller circuit or Microcontroller Motor Pumps Figure 1. System block diagram of DTMF based motor pump controller Figure 2. The DTMF tones generated from a Phone Keypad The transmitted DTMF tone from a transmitting phone station is received at the receiving station and be identified by a suitable DTMF decoder circuit. In this and our previous work, we focused on the implementation of the DTMF decoder using analog electronic circuits. In the sequel, we give the designed circuit of each stages supported by experimental test and results for the different stages of the overall proposed design. A. DTMF Tone Generator 3 DTMF SIGNAL AND DECODER Each digit of the telephone keypad is represented by two simultaneous tones selected from a set of frequencies. One set of frequencies consists the low frequencies (697 Hz, 770 Hz, 852 Hz, 91 Hz) and the second set consists of the high frequencies (1209 Hz, 1336 Hz, 177 Hz, 1633 Hz) as shown in Figure 2. Each time when we press a digit or symbol on the phone keypad, a sinusoid signal, which is a sum of the lower frequency (f L ) and the higher frequency (f H ) is generated. Therefore, the DTMF tone signal generated corresponding to a certain pressed digit on the keypad is given by: x( t) Asin(2 f t) Bsin(2 f t) (1) L where A & B are the amplitude of the each frequency sinusoid. The discrete time version of H From (1), the DTMF tone signal is the sum of two sinusoid frequencies. For the experimental work, we designed an op-amp adder circuit that produces the sum of the two sinusoid signals at the output of the op-amp. The two inputs of the adder circuit are supplied from two function generators, one supplying a sinusoidal voltage at the lower frequency f L, and the second supplying a sinusoidal voltage at the higher frequency f H. Figure 3 shows the circuit diagram of a noninverting summer op-amp circuit [9]. The circuit generates the DTMF tone when the digit 0 is pressed on the keypad of the telephone. The two generator sources produce sinusoidal voltages of 91 Hz and 1336 Hz. Let the sinusoidal voltage at 91 Hz and 36 Hz as V91(t) and V1336(t) respectively, the output voltage of the summer op-amp (with R1 = R2 = R1= R23) will be V0(t)= V91 (t)+ V1336 (t). Figure shows the resultant signal at the output of the non-inverting ISBN: SDIWC 53

the resultant magnitude will be very small near to zero when they are out of phase or summed destructively. V91 V1336 1 Vpk 91 Hz 0 Figure 3.

3 amplifier. As can be evident from the Figure, the resultant amplitude (Channel 2 of Oscilloscope) will be nearly twice of the individual amplitudes when the two signals are in-phase or summed constructively and the resultant magnitude will be very small near to zero when they are out of phase or summed destructively. V91 V Vpk 91 Hz 0 Figure 3. DTMF Tone Generating Circuit R1 R2 1 Vpk 1336 Hz 0 R1 - LM32AJ U5A 2 R23 3 "Digit 0 tone " 1 V0 parameters are selected to have resonance or maximum gain at a frequency of 177 Hz, which is one of the eight DTMF frequencies. We will have eight fourth order bandpass filters corresponding to the eight DTMF frequencies. The values of the components for Figure 5 are determined for bandwidth, B = 100 Hz (quality factor, Q =100/91), C = C12 =C13 = C1 = C =100 nf and overall gain of Am =2. We used B = 100 Hz for the higher frequency DTMF frequencies (91 Hz, 1209 Hz, 1336, 177 Hz) and a bandwidth of B = 60 Hz for the low frequencies (697 Hz, 770 Hz, 852 Hz). Several simulation trials have been done for different bandwidth specifications, selection of a higher bandwidth for the higher frequencies will provide a stable result compared with using the same bandwidth specifications for all DTMF frequencies. This is because the bandwidth has to be increased to get a comparable quality factor for the higher frequencies compared with the lower DTMF frequencies. C12 C1 R k R k R.53k R10 26 C UC 10.99k LM32AJ R13 C13 R LM32AJ 1 U9D Vbp(t) Figure 5. Fourth order multiple feedback topology active bandpass filter (component values are for mid or center frequency, fm =177 Hz). Figure. DTMF tone corresponding to the digit 0 at the output of the non-inverting summer shown in Fig. 3, Channel 1 of Oscilloscope (CH1, Yellow color-1336 Hz) and Channel 2 of Oscilloscope (CH2, Blue color- 91 Hz Hz). B. Four-Pole Active Bandpass Filter The next step after generating the DTMF tone signals is to design a DTMF decoder circuit that is able to identify the individual DTMF tone signals. We used a four-pole active band pass filter based on the multiple feedback topology and the four-pole bandpass filter can be designed from a cascade or series connection of two identical two-pole multiple feedback topologies. The capacitor and resistance values can be determined using the design steps as mentioned in [10]. Figure 5 shows a fourth order Butterworth active bandpass filter where the Figure 6. Output of the bandppass filter of center frequency fm =177 Hz for DTMF tone input signal corresponding to digit 3 (yellow color:- input signal of 697 Hz Hz & blue color:- output signal of 177 Hz). ISBN: SDIWC 5

Figure 6 shows the output of the active bandpass filter shown in Figure 5 when the DTMF signal for digit 3 is passed through the bandpass filter (yellow-colored graph), which has a center frequency

Similarly, Figure 7 shows the output of the active bandpass filter designed for a center frequency of fm = 697 Hz when the DTMF signal for digit 3 is an input signal to the filter.

4 Figure 6 shows the output of the active bandpass filter shown in Figure 5 when the DTMF signal for digit 3 is passed through the bandpass filter (yellow-colored graph), which has a center frequency fm = 177 Hz. It clearly shows that the circuit filters the input DTMF tone corresponding to the digit 3 and produces the sinusoid signal of frequency 177 Hz at its output (blue-colored graph). Similarly, Figure 7 shows the output of the active bandpass filter designed for a center frequency of fm = 697 Hz when the DTMF signal for digit 3 is an input signal to the filter. It clearly shows that the circuit filters the input DTMF tone corresponding to the digit 3 and produces the sinusoid signal of frequency 697 Hz at its output (blue-colored graph). Therefore, the two active bandpass filters (center frequency fm =697 Hz and fm =177 Hz) together are used to recognize or decode that the dialed digit is digit 3. Figure 7. Output of the bandppass filter of center frequency fm =697 Hz for DTMF tone input signal corresponding to digit 3 (yellow color:- input signal 697 Hz Hz & blue color:- output signal of 697 Hz). The accuracy of the bandpass filters can be studied by looking the output of the filters when a DTMF tone signal different from the center frequency of the bandpass filter is an input to the filter. For example, Figure 8 shows the output of the bandpass filter with center frequency fm =177 Hz when an input DTMF tone signal corresponding to digit 7 (852 Hz Hz) is an input to the filter. Clearly, the output signal (blue color) is significantly attenuated by the filter and hence weak amplitude, which is unable to make the comparator output high: the next stage of the decoder circuit. Figure 8. Output of the bandpass filter of center frequency fm =177 Hz for DTMF tone input signal corresponding to digit 7 (yellow color:- input signal 852 Hz Hz & blue color:- output signal of the filter). C. The Comparator, Integrator and Buffer Circuit The active filter circuit designed as shown in Figure 5 attenuates other DTMF frequencies that are different from the center or the resonance frequency and therefore there will be very small amplitude signal at the output for the frequencies different from the resonant frequency. For instance, if the digit 3 is pressed, only the active bandpass filter with the parameters as shown in in Figure 5. produces a high amplitude signal at its output compared with the output of the filters designed for the other DTMF frequencies. For this reason, we designed a comparator circuit following the bandpass filter and then an RC integrator circuit and buffer to produce HIGH voltage (+) for the DTMF frequencies corresponding to the pressed digit and a LOW voltage (0 V) for the other filters. Figure 9. shows the comparator circuit, followed by the integrator RC circuit, buffer logic gate (U2D) and at the end a olt indicator lamp (X3) for indicating the detection of the DTMF frequency. The potentiometer is set for a reference voltage of approximately 0. and the comparator gives an output voltage of (HIGH) when the output of the bandpass filer is above 0. and an output voltage of -15V (LOW) when the bandpass output voltage is less than the 0.. The output of the comparator will be a square wave. Fig. 10 shows the output voltage (close to ) of the RC integrator circuit output after detecting the 177 Hz DTMF frequency. ISBN: SDIWC 55

Clearly, the signal is nearly zero amplitude showing that the DTMF frequencies corresponding to digit 7 are no more recognized (don t pass through) by the bandpass filter of center frequency 177 Hz.

5 Vbp(t) R32 100k Key=D 1% 5 LM32AJ U10B 6 7 1N007GP D3 R33 1k C15 Figure 9. A comparator, integrator and buffer circuit R3 U2D 050BT_15V 100k 177 Hz X3 corresponding to digit 7 (852 Hz+1209 Hz) is an input to the filter. Clearly, the signal is nearly zero amplitude showing that the DTMF frequencies corresponding to digit 7 are no more recognized (don t pass through) by the bandpass filter of center frequency 177 Hz. This shows a particular bandpass filter, comparator and integrator circuit assembly is tuned for recognizing a particular DTMF frequency and hence clearly showing the strength of the overall decoder circuit. Figure 10. Integrator circuit output signal after the bandpass filter of center frequency fm =177 Hz for DTMF tone input signal corresponding to digit 3, (blue color:- integrator output signal& yellow color:- output signal of buffer). The output of the buffer (U2D) will be HIGH () if a DTMF frequency is detected and LOW (0 V) if a DTMF frequency isn t detected. For example, the output of the buffer shown in Figure 9 will be for the integrator input signal shown in Figure 10, which means recognition of the tone corresponding to 177 Hz. In other words, when digit 3 is pressed on the telephone keypad and transmitted from the DTMF transmitter, only the buffer logic gates corresponding to 697 Hz and 177 Hz bandpass filters are HIGH (logic 1) and all other buffer outputs are LOW (logic zero). In this way, all the low and high DTMF frequencies are recognized and hence any dialed digit can be decoded by the joint function of the bandpass filters, comparators, integrator and logic gate circuits corresponding to its own DTMF frequencies. For comparison purposes, Figure shows the output of the comparator and integrator circuit after the bandpass filter with center frequency fm = 177 Hz when the DTMF tone signal Figure. Integrator circuit output signal after the bandpass filter of center frequency fm =177 Hz for DTMF tone input signal corresponding to digit 7 (input DTMF tone= 852 Hz+1209 Hz), (blue color:- integrator output signal& yellow color:- output signal of buffer). Table 1. shows the list of the components used for the DTMF decoder circuit. Table 1. List of components used to build each of DTMF tone generators, four-pole active bandpass filter, and comparator-integrator-buffer circuit Circuits Type of components Quantity of components DTMF Tone Generator Four-Pole Active Bandpass Filter Comparator- Integrator- Buffer Circuit Op-AMp 1 Resistors Op-Amp 2 Multi turn Variable Resistors Capacitors Op-Amp 1 Variable Resistor 1 Resistors 2 Capacitor 1 Diode 1 Buffer 1 6 ISBN: SDIWC 56

6 D. LOGIC CONTROLLER CIRCUIT In the above experimental work and analysis, we have shown the possibility of complete detection and recognition of the DTMF frequencies using the designed DTMF decoder circuit. We get a logic 1 if a DTMF frequency is recognized and a logic 0 if a DTMF frequency isn t detected or recognized by the decoder electronic circuit. The logic controller controls the four motor pumps assumed to be located in four different locations in a certain agricultural site. When digit 1 is pressed or the DTMF tone corresponding to the digit is transmitted, all four motors will be functional (ALL SWITCHED ON). When digit 0 is pressed, all four motor pumps will stop working (ALL SWITCHED OFF). When digit 2, digit 3, digit and digit 5 are pressed, Motor-one, Motor-two, Motor-three and Motor-four respectively are separately activated (SWITCHED ON) and start working. When digit 6, digit 7, digit 8 and digit 9 are pressed, Motor-one, Motor- two, Motor- three and Motor-four respectively are separately deactivated (SWITCHED OFF) and stop working. When a particular motor is switched on, it remains in switched on state unless it is switched off by a transmitted switched off command and vice versa. Therefore, there is a need for tracking the state of the motor and hence a requirement not only a combinational but also a sequential circuit. The sequential switching states of the motors are controlled by the JK flip flops and the detail design and analysis for logic controller circuit can be referred in the simulation work as presented in [8]. CONCLUSTION This paper investigates the experimental analysis and validation of an electronic circuit designed for controlling remotely located agricultural motor pumps based on the DTMF signaling technique. This experimental work is an extension of the theoretical design and MULTISIM simulation of the different stages of the proposed system as presented in [8]. The DTMF decoder is designed from discrete electronic components and the functionality of the overall circuit is tested using the NI- MULTSIM simulation previously and experimentally in the present work. Full motor switching state control is achieved using the designed circuit. This proposed electronic design can be used for remotely controlling motor pumps used for agricultural site without requiring the physical presence of the farmer or the user at the site. As a result, the use of the system achieves proper water management, saves time, human power, resources and related costs required for not using a remote control system. The system and the technique can be adopted and used for remotely controlling any home or industrial applications. REFERENCES [1] Faisal Baig, Saira Beg, Muhammad Fahad Khan Controlling Home Appliances Remotely through Voice Command, International Journal of Computer Applications, Vol. 8, No.17, June [2] Tuljappa M Ladwa, Sanjay M Ladwa, R Sudharshan Kaarthik, Alok Ranjan Dhara, Nayan Dalei, Control of Remote Domestic System Using DTMF, Proceedings of ICICI-BME 2009, pp [3] lsmail Cogkun and Hamid Ardam, A remote controller for home and office appliances by telephone, IEEE Transactions on Consumer Electronics, Vol., No., pp , November [] Rohit Sharma, Kushagra Kumar and Shashank Vig, DTMF Based Remote Control System, IEEE International Conference on Industrial Technology (ICIT) 2006, pp [5] Haeil Hyun1, Jonghyun Park1, Yunchan Cho1, Jae Wook Jeon2, PC Application Remote Control via Mobile Phone, International Conference on Control, Automation and Systems 2010, Oct , 2010 in KINTEX, Gyeonggi-do, Korea pp [6] Vandana Dubey, Nilesh Dubey, Shailesh singh Chouhan Wireless Sensor Network based Remote Irrigation Control System and Automation using DTMF code, International Conference on Communication Systems and Network Technologies (CSNT), pp. 3-37, 3-5 June 20 [7] Jia Uddin1, S.M. Taslim Reza2, Qader Newaz2, Jamal Uddin2, Touhidul Islam2, and Jong-Myon Kim, Automated Irrigation System Using Solar Power, 7th International Conference on Electrical and Computer Engineering, December, 2012, Dhaka, Bangladesh. [8] Beza N. Getu, Nasser A. Hamad, Hussain A. Attia, Remote Controlling of an Agricultural Pump System Based on the Dual Tone Multi-Frequency (DTMF) Technique, Accepted for Publications (October 201) in Journal of Engineering Science & Technology (JESTEC), Taylor's University, Malaysia. [9] David L. Terrell, OP AMPS Design, Application, and Troubleshooting, Second Edition, 1996, Butterworth- Heinemann, Elsevier Science. [10] Ron Mancini, Editior in Chief, Op-Amps for Everyone, Texas Instruments, August ISBN: SDIWC 57

REMOTE CONTROLLING OF AN AGRICULTURAL PUMP SYSTEM BASED ON THE DUAL TONE MULTI-FREQUENCY (DTMF) TECHNIQUE

Journal of Engineering Science and Technology Vol. 10, No.10 (2015) 1261-1274 School of Engineering, Taylor s University REMOTE CONTROLLING OF AN AGRICULTURAL PUMP SYSTEM BASED ON THE DUAL TONE MULTI-FREQUENCY