Tuesday, 19 March 2013

MOBILE BASED DC MOTOR SPEED CONTROL




DC MOTOR SPEED CONTROL USING MOBILE (P.W.M TECHNIQUE)



Now a day's every system is automated in order to face new challenges in the present day situation. Automated systems have less manual operations, so that the flexibility, reliabilities are high and accurate. Hence every field prefers automated control systems. Especially in the field of electronics automated systems are doing better performance.

 This project mainly deals with the speed control of a DC Motor using a MOBILE. The type of speed control that has been chosen here is pulse width modulation PWM. This project deals with development of DC MOTOR control using MOBILE, where a message is send to the GSM interfaced to the MCU. 12V DC Motor drives widely use  Micro controllers and  The project detail design and complete hardware based high performance DC drive control system  will be  implemented. Most recently new requirements have arisen. These include faster torque control update with flexible design capability of motion peripherals for high performance military drive applications. Pulse width modulation type of speed control is chosen here because of high accuracy, high reliability, quick response and high efficiency.

This project deals with the types of problems that we face due to disturbances in supply voltage or load on the motor and enables us to overcome these difficulties by helping us with the appropriate software and hardware.We propose to design an embedded controller that helps us maintain the speed of the DC machine within the specific limits and a remote operate the embedded controller. Here, the pulses from the remote are sensed by sensor and are transmitted to the embedded controller. This controller contains a programmable PWM port. The output of this PWM port is used to control power delivered by a power regulating   device


MOBILE BASED DC MOTOR SPEED CONTROL


HARDWARE COMPONENTS:

 1. AT8952 MICROCONTROLLER
2. GSM MODEM.
3. ULN2003.                
4. MAX232.
5. DC MOTOR



1.AT8952 MICROCONTROLLER

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes of in-system programmable Flash memory. The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard 80C51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer.
By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications.

PIN DESCRIPTION:
VCC: Supply voltage.
GND: Ground.

 Port 0:

 Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-impedance inputs. Port 0 can also be configured to be the multiplexed low-order address/data bus during accesses to external program and data memory. In this mode, P0 has internal pull-ups. Port 0 also receives the code bytes during Flash programming and outputs the code bytes during program verification. External pull-ups are required during program verification. 

Port 1:

 Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown in the following table. Port 1 also receives the low-order address bytes during Flash programming and verification.       

Port 2:

 Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @ DPTR). In this application, Port 2 uses strong internal pull-ups when emitting 1s. During accesses to external data memory that uses 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.

 Port 3:

 Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull-ups. Port 3 receives some control signals for Flash programming and verification. Port 3 also serves the functions of various special features of the AT89S52, as shown in the following table.

RST: 

Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device. This pin drives high for 98 oscillator periods after the Watchdog times out. The DISRTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In the default state of bit DISRTO, the RESET HIGH out feature is enabled.

ALE/PROG: 

Address Latch Enable (ALE) is an output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.

PSEN:

 Program Store Enable (PSEN) is the read strobe to external program memory. When the AT89S52 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.

EA/VPP:

 External Access (EA) must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming.

XTAL1:
Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2: Output from the inverting oscillator amplifier.

TIMER/COUNTERS:

The Atmel 80S52 Microcontroller implements two general purposes, 16-bit timers/counters. They are identified as Timer 0 and Timer 1, and can be independently configured to operate in a variety of modes as a timer or as an event counter. When operating as a timer, the timer/counter runs for a programmed length of time, and then issues an interrupt request. When operating as a counter, the timer/counter counts negative transitions on an external pin. After a preset number of counts, the counter issues and interrupt request. The various operating modes of each timer/counter are described in the following sections

TIMER/COUNTER OPERATIONS:

A basic operation consists of timer registers THx and TLx (x= 0, 1) connected in cascade to form a 16-bit timer. Setting the run control bit (TRx) in TCON register turns the timer on by allowing the selected input to increment TLx. When TLx overflows it increments THx; when THx overflows it sets the timer overflow flag (TFx) in TCON register. Setting the TRx does not clear the THx and TLx timer registers. Timer registers can be accessed to obtain the current count or to enter preset values. They can be read at any time but TRx bit must be cleared to preset their values, otherwise the behavior of the timer/counter is unpredictable. The C/Tx control bit (in TCON register) selects timer operation, or counter operation, by selecting the divided-down peripheral clock or external pin Tx as the source for the counted signal. TRx bit must be cleared when changing the mode of operation; otherwise the behavior of the timer/counter is unpredictable. 

For timer operation (C/Tx = 0), the timer register counts the divided-down peripheral clock. The timer register is incremented once every peripheral cycle (6 peripheral clock periods). The timer clock rate is FPER / 6, i.e. FOSC / 12 in standard mode or FOSC / 6 in X2 modes. For counter operation (C/Tx# = 1), the timer register counts the negative transitions on the Tx external input pin. The external input is sampled every peripheral cycle. When the sample is high in one cycle and low in the next one, the counter is incremented. Since it takes 2 cycles (12 peripheral clock periods) to recognize a negative transition, the maximum count rate is FPER / 12, i.e. FOSC / 24 in standard mode or FOSC / 12 in X2 mode. There are no restrictions on the duty cycle of the external input signal, but to ensure that a given level is sampled at least once before it changes, it should be held for at least one full peripheral cycle. In addition to the “timer” or “counter” selection, Timer 0 and Timer 1 have four operating modes from which to select which are selected by bit-pairs (M1, M0) in TMOD. Modes 0, 1, and 2 are the same for both timer/counters. Mode 3 is different. The four operating modes are described below. Timer 2 , has three modes of operation:  ‘capture’, ‘auto-reload’ and ‘baud rate generator’.

GSM Modem:

A GSM modem is a wireless modem that works with a GSM wireless network. A wireless modem behaves like a dial-up modem. The main difference between them is that a dial-up modem sends and receives data through a fixed telephone line while a wireless modem sends and receives data through radio waves.

A GSM modem can be an external device or a PC Card / PCMCIA Card. Typically, an external GSM modem is connected to a computer through a serial cable or a USB cable. A GSM modem in the form of a PC Card / PCMCIA Card is designed for use with a laptop computer. It should be inserted into one of the PC Card / PCMCIA Card slots of a laptop computer.Like a GSM mobile phone, a GSM modem requires a SIM card from a wireless carrier in order to operate.

A SIM card contains the following information:

  • Subscriber telephone number (MSISDN)
  • International subscriber number (IMSI, International Mobile Subscriber Identity)
  • State of the SIM card
  • Service code (operator)
  • Authentication key
  • PIN (Personal Identification Code)
  • PUK (Personal Unlock Code)
Computers use AT commands to control modems. Both GSM modems and dial-up modems support a common set of standard AT commands. In addition to the standard AT commands, GSM modems support an extended set of AT commands. These extended AT commands are defined in the GSM standards. With the extended AT commands, the following operations can be performed:

        Reading, writing and deleting SMS messages.
        Sending SMS messages.
        Monitoring the signal strength.
        Monitoring the charging status and charge level of the battery.
        Reading, writing and searching phone book entries.

power supply

              The input to the circuit is applied from the regulated power supply. The a.c. input i.e., 230V from the mains supply is step down by the transformer to 12V and is fed to a rectifier. The output obtained from the rectifier is a pulsating d.c voltage. So in order to get a pure d.c voltage, the output voltage from the rectifier is fed to a filter to remove any a.c components present even after rectification. Now, this voltage is given to a voltage regulator to obtain a pure constant dc voltage.

Transformer:

Usually, DC voltages are required to operate various electronic equipment and these voltages are 5V, 9V or 12V. But these voltages cannot be obtained directly. Thus the a.c input available at the mains supply i.e., 230V is to be brought down to the required voltage level. This is done by a transformer. Thus, a step down transformer is employed to decrease the voltage to a required level.

Rectifier:
The output from the transformer is fed to the rectifier. It converts A.C. into pulsating D.C. The rectifier may be a half wave or a full wave rectifier. In this project, a bridge rectifier is used because of its merits like good stability and full wave rectification.

Filter:
Capacitive filter is used in this project. It removes the ripples from the output of rectifier and smoothens the D.C. Output   received from this filter is constant until the mains voltage and load is maintained constant. However, if either of the two is varied, D.C. voltage received at this point changes. Therefore a regulator is applied at the output stage.

Voltage regulator:
          As the name itself implies, it regulates the input applied to it. A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. In this project, power supply of 5V and 12V are required. In order to obtain these voltage levels, 7805 and 7812 voltage regulators are to be used. The first number 78 represents positive supply and the numbers 05, 12 represent the required output voltage levels.

Max 232
            Max232 IC is a specialized circuit which makes standard voltages as required by RS232 standards. This IC provides best noise rejection and very reliable against discharges and short circuits. MAX232 IC chips are commonly referred to as line drivers. To ensure data transfer between PC and microcontroller, the baud rate and voltage levels of Microcontroller and PC should be the same. The voltage levels of microcontroller are logic1 and logic 0 i.e., logic 1 is +5V and logic 0 is 0V. But for PC, RS232 voltage levels are considered and they are: logic 1 is taken as -3V to -25V and logic 0 as +3V to +25V. So, in order to equal these voltage levels, MAX232 IC is used. Thus this IC converts RS232 voltage levels to microcontroller voltage levels and vice versa.

ULN2003

The ULN2003 is high voltage, high current Darlington arrays each containing seven open collectors Darlington pairs with common emitters. Each channel rated at 500mAand can withstand peak currents of 600mA.Suppressiondiodesare included for inductive load driving and the inputs are pinned opposite the outputs to simplify board layout.

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.



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