SPEED REGULATION OF DC DRIVE USING MOBILE COMMUNICATION

SPEED REGULATION OF DC DRIVE USING MOBILE COMMUNICATION

ABSTRACT

The importance of the speed control of DC motors in manufacturing industries like plastic, textile, chemical and pharmaceutical hardly needs any emphasis as it ensures efficient and consistent production. In this paper, the authors present implementation of a hardware circuit which is designed for remote speed control of a DC motor by using Dual Tone Multi Frequency (DTMF) tone of mobile phone. The hardware circuit includes the use of DTMF decoder IC MT8870 and Relay driver IC ULN2003. The mobile keypad keys have been mapped to the speeds of ‘High Speed’, ‘Medium Speed’, ‘Low Speed’ and ‘Stop’ to regulate the speed of DC motor.

Keywords- DC motor, DTMF, IC MT8870, IC ULN2003

INTRODUCTION

A DC motor generates torque directly from DC power supplied to the motor by using internal commutation, stationary permanent magnets and by rotating electrical magnets. It works on the principle of Lorentz force according to which any current carrying conductor placed within an external magnetic field experiences a torque or force known as Lorentz force. The latest development in DC drives are the brushless DC drives, advantages of a brushed DC motor include low initial cost, higher reliability and simple control of motor speed. DC motors can be used as DC drives in various applications requiring adjustable speed as well as good speed regulation and frequent starting-braking-reversing. Some important industrial applications of DC drives are rolling mills (paper, steel), mine winders, hoists, machine tools, traction, printing presses, textile mills, excavators and cranes. There are great number of methods which can be used to control the speed of DC motors. If a DC motor operates with the remote control by the mobile phone it is obviously advantageous for the industry. In this project, speed control of a DC motor is ensured by using Dual Tone Multi Frequency (DTMF) tone of mobile phone. The DTMF is a method of representing digits with tone frequencies in order to transmit them over an analog communication network. The tone received by mobile headphone is processed by DTMF decoder IC MT8870 which decodes into equivalent binary. This binary signal is further sent to relay driver IC ULN2003 to ON/OFF the relays according to the key pressed by the user which is responsible for controlling the speed of DC motor.

 

Fig.1: Block diagram of remote speed control of a DC motor by Mobile

CIRCUIT ILLUSTRATION

A. Circuit Introduction

This process works when a mobile phone initiates a call for the other mobile phone on any network which is connected with the receiver end in auto answer mode. During this outgoing call if a key is pressed the associated key generates dual tone multiple frequency (DTMF) at the other end. The received tone is processed by DTMF decoder IC MT8870. A specific frequency consisting of two separate tones is assigned by the DTMF decoder. It produces two different frequencies from lower band and upper band frequencies. For example, if the user presses a key„2‟ it will send a tone comprising of 697 Hz and 1336 Hz to the other end of the system. Then the decoder produces an equivalent binary digit after decoding the DTMF tone [5]. This binary number goes to relay driver IC ULN2003, which drives the relays and produces the output for DC motor. Crucial components used in this project are DTMF decoder (MT8870), Relay driver (ULN2003) and Voltage regulator (7805). When mobile headphone output is connected to pin 2 (IN-) in a single- ended input configuration it is recognised to be effective, a correct 4-bit decoded signal corresponding to the DTMF tone is transferred to pin 11 (Q1) - pin 14 (Q4) outputs. Q1-Q4 pins of the DTMF decoder are connected to input pins (1 B - 4 B) of relay driver IC ULN2003 respectively. Pin 1 (IN+) and pin 4 ( ) of DTMF decoder IC MT8870 are shorted. Binary output from MT8870 is not sufficient for operating the relays directly since the magnitude of output current is very low. Thus, the authors have used ULN2003 for current amplification purposes. A 3.597 MHz crystal oscillator is used for providing clock input to MT8870. The output from Voltage regulator (7805) i.e. 5 V is given to MT8870 . The Circuit layout on which the hardware has been implemented is shown in Figure 2. ref V

 

Fig.2: Circuit layout

B. DTMF decoder MT8870

MT8870 is a complete DTMF receiver. It integrates the band split filter and digital decoder functions. The filter section uses switched capacitor techniques for high and low group filters. The decoder uses digital counting techniques to detect and decode all 16 DTMF tone pairs into a 4-bit code. This DTMF receiver minimizes external component count by providing an on-chip differential input amplifier, clock generator and a latched three-state interface bus [6]. The MT8870 monolithic DTMF receiver offers small size, low power consumption and high performance. Its architecture consists of a band split filter section, which separates the high and low group tones, followed by a digital counting section which verifies the frequency and duration of the received tones before passing the corresponding code to the output bus. The DTMF technique presents distinct representation of 16 common alphanumeric (0-9, A-D, *, #) on the mobile phone. The lowest frequency used is 697 Hz and the highest frequency used is 1633 Hz. The DTMF keypad is arranged in such a way that each row will have its own unique tone frequency and also each column will have its own unique tone frequency. The frequency assignments in a DTMF system are shown in Table 1.

Table1: Frequency assignments in a DTMF system

 

Among the keys specified in Table 3, only 4 different keys have been used to serve the purpose of controlling the speed. The Table 2 shows the action performed corresponding to the keys pressed.

Table2: Function assigned for the key

 

Table3: DTMF data output

 

For DTMF decoding in the project, the circuit used is Single Ended Input configuration as shown in Figure 3. Pin Description of IC MT8870 is illustrated in Table 4. The functional block diagram of MT8870 is shown in Figure 4.

 

Fig.3: Single Ended Input Configuration of MT8870

PIN DESCRIPTION

Table4: Pin Description of MT8870

 

Fig.4: Functional block diagram of MT8870

C. Relay driver ULN2003

ULN2003 is a high voltage and high current Darlington array IC. It contains seven open collector Darlington pairs with common emitters. A Darlington pair is an arrangement of two bipolar transistors. ULN2003 belongs to the family of ULN200X series of ICs. Different versions of this family interface to different logic families. ULN2003 is for 5V TTL, CMOS logic devices. Each channel or Darlington pair in ULN2003 is rated at 500mA and can withstand peak current of 600mA. The inputs and outputs are provided opposite to each other in the pin layout. Each driver also contains a suppression diode to dissipate voltage spikes while driving inductive loads. Applications include relay drivers, hammer drivers, lamp drivers, display drivers (LED gas discharge), line drivers, and logic buffers. The ULN2003 has a 2.7kW series base resistor for each Darlington pair for operation directly with TTL or 5V CMOS devices. These versatile devices are useful for driving a wide range of loads including solenoids, relays DC motors, LED displays filament lamps, thermal print heads and high power buffers. The schematic for each driver is shown in Figure 5.

 

Fig.5: Schematic for each driver

The logic diagram of ULN2003 is shown in Figure 6 and the Pin Description of ULN2003 is illustrated in Table 5.

 

Fig.6: Logic Diagram of ULN2003

PIN DESCRIPTION

 

Table5: Pin Description of ULN2003

HARDWARE DESIGN

The circuit layout of remote speed control of a DC motor by mobile shown in Figure 2 has been implemented in hardware as illustrated in the Figure 7.

 

Fig.7: Hardware design for remote speed control of a DC motor by mobile

CONCLUSION

We have discussed and successfully demonstrated the purpose, use and implementation of mobile communication system to control speed of DC motor from remote area using mobile. To achieve this, we have used the concept of relay operation using decoding of DUAL TONE MULTI-FREQUENCY SIGNALING (DTMF) produced by mobile. We have designed a hardware module connected with a prototype load as DC motor and have performed precise control and speed tests as well as braking. Its efficiency is relatively high as compared to the other similar methods.

REFERENCES

[1] G.K. Dubey, “Fundamentals of Electrical drives”,Narosa Publishing House Pvt. Ltd., 2nd edition, PP:60, 2011, ISBN 978-81-7319-428-3.

[2] S. M. Bashi, I. Aris and S.H. Hamad, “Development of Single Phase Induction Motor Adjustable Speed Control Using M68HC11E-9 Microcontroller,” Journal of Applied Sciences 5 (2), pp. 249-252.

[3] T. Kenjo and A. sugawara, “stepping motors and their Microprocessor controls”, 2nd Edition, Oxford university press, 1994.

[4] R.Siwy, "Generation and Recognition of DTMF Signals with the Microcontroller MSP430", Texas Instruments Deutschland GmbH SLAAE16 (October 1997)

[5] M.K. Parai, D.Misra, B.Das, “CPLD Based Speed Control Of DC Motor Operated through Cellphone” , International Journal of Soft Computing and Engineering, ISSN: 2231-2307, Volume-2, Issue-4, September 2012.

[6] http://www.datasheetcatalog.com/datasheets_pdf/M/T/8/8/MT8870.sh tml

[7] http://www.datasheetcatalog.com/datasheets_pdf/U/L/N/2/ULN2003. shtml

[8] M.R.Chaurasia, N.Naiyar , “Stepper Motor Controller using XC9572 CPLD through Mobile As a Remote” , International Journal of Soft Computing and Engineering, ISSN: 2231-2307, Volume-1, Issue-6, January 2012.

[9] S. Khakurel, A. Kumar Ojha , S.Shrestha, R.N. Dhavse “Mobile Controlled Robots for regulating DC motor s and their Domestic Application” International Journal of Scientific and Engineering Reserch, Volume 1, Issue 3, December 2010 1 ISSN 2229-5518.