ROBOTICS

COMPONENTS USED

 

• Microcontroller(AT89C52)
  
• Voltage Comparator(LM311P)
  
• Motor Driver(L293D)
  
• Variable Resistance
  
• IR Sensor(GP2D12)
  
• Crystal Oscillator(ML 11.0592)
  
• Voltage Regulator(LM7805)
  

    
 

 

 

 

 

 

 

MICROCONTROLLER

(AT89C52 24PI)

The AT89C52 is a low-power, high-performance CMOS 8-bit microcomputer with 8 Kbytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel's high density nonvolatile memory technology and is compatible with the industry standard 80C51 and 80C52 instruction set and pinout.

 

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 Flash on a monolithic chip, the Atmel AT89C52 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.

 

AT89C51 24PI

 

The AT89C52 provides the following standard features: 8 Kbytes of Flash, 256 bytes of RAM, 32 I/O lines, three 16- bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89C52 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power Down Mode saves the RAM contents but freezes the oscillator, disabling all other chip functions until the next hardware reset.

 

 

                 Pin Configuration

 

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 pullups.
  

  
   

  
   

• Port 0 also receives the code bytes during Flash programming and outputs the code bytes during program verification. External pullups are required during program verification.
  

 

 

 

Port 1

 

• Port 1 is an 8-bit bidirectional I/O port with internal pullups.
  

  
   

• 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 pullups 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 pullups.
  

  
   

  
   

• 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 program verification.
  

  
   

 

Port 2

 

• Port 2 is an 8-bit bidirectional I/O port with internal pullups.
  

  
   

• 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 pullups 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 pullups.
  

  
   

• 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 pullups when emitting 1s. During accesses to external data memory that use 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 pullups.
  

  
   

• 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 pullups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups.
  

  
   

• Port 3 also serves the functions of various special features of the AT89C51, as shown in the following table.
  

  
   

 

 

• Port 3 also receives some control signals for Flash programming
  

  and programming verification.
  

 

 

RST

 

Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device.

 

 

 

 

ALE/PROG

 

Address Latch Enable 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 microcrontroller is in external execution mode.

 

 

PSEN

 

Program Store Enable is the read strobe to external program memory. When the AT89C52 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 Enable. 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 when 12-volt programming is selected.

 

 

 

 

 

XTAL1

 

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

 

XTAL2

 

Output from the inverting oscillator amplifier.

 

 

 

 

 

 

BLOCK DIAGRAM OF AT89C52

 

Block Diagram of Microcontroller(AT89C52)

 

Interrupts

 

The AT89C52 has a total of six interrupt vectors: two external interrupts (INT0 and INT1), three timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. These interrupts are all shown in Figure below. Each of these interrupt sources can be individually enabled or disabled by setting or clearing a bit in Special Function Register IE. IE also contains a global disable bit, EA, which disables all interrupts at once. Note that Table below shows that bit position IE.6 is unimplemented. In the AT89C51, bit position IE.5 is also unimplemented. User software should not write 1s to these bit positions, since they may be used in future AT89 products. Timer 2 interrupt is generated by the logical OR of bits TF2 and EXF2 in register T2CON. Neither of these flags is cleared by hardware when the service routine is vectored to. In fact, the service routine may have to determine

whether it was TF2 or EXF2 that generated the interrupt, and that bit will have to be cleared in software.

 

 

 

 

Oscillator Characteristics

 

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that can be configured for use as an on-chip oscillator, as shown in Figure below. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven, as shown in Figure below. There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.

 

 

 

Crystal Oscillator

 

 

ML 11.0592 crystal Oscillator

 

 

 

 

Maximum rating of AT89C51

 

 

 

VOLTAGE COMPARATOR

(LM311P)

 

The LM311 are single high-speed voltage comparators. These devices are designed to operate from a wide range of power-supply voltages, including 15-V supplies for operational amplifiers and 5-V supplies for logic systems. The output levels are compatible with most TTL and MOS circuits. These comparators are capable of driving lamps or relays and switching voltages up to 50 V at 50 mA. All inputs and outputs can be isolated from system ground. The outputs can drive loads referenced to ground, VCC+ or VCC–. Offset balancing and strobe capabilities are available, and the outputs can be wire-OR connected. If the strobe is low, the output is in the off state, regardless of the differential input.

 

 

 

 

 

                    LM 311 voltage comparator

 

 

 

                    Pin Configuration of LM311

 

 

 

 

Functional Block Diagram

 

                        

 

 

MOTOR DRIVER

(L293D)

 

The Device is a monolithic integrated high voltage, high current four channel driver designed to accept standard DTL or TTL logic levels and drive inductive loads (such as relays solenoides, DC and stepping motors) and switching power transistors. To simplify use as two bridges each pair of channels is equipped with an enable input. A separate supply input is provided for the logic, allowing operation at a lower voltage and internal clamp diodes are included.

 

 

 

 

 

 

 

BLOCK DIAGRAM

 

 

 

                    L293D Motor Driver

 

The L293D is a quadruple half H-bridge bidirectional motor driver IC that can drive current of up to 600mA with voltage range of 4.5 to 36 volts. It is suitable to drive small DC-Geared motors, bipolar stepper motor etc.

Specifications

• Supply Voltage Range 4.5V to 36V
  
• 600-mA Output current capability per driver
  
• Separate Input-logic supply
  
• It can drive small DC-geared motors, bipolar stepper motor.
  
• Pulsed Current 1.2-A Per Driver
  
• Thermal Shutdown
  
• Internal ESD Protection
  
• High-Noise-Immunity Inputs
  

Applications

• DC and stepper motor drives
  
• Position and velocity servomechanisms
  

 

PIN CONFIGURATION

 

Pin configuration of L293D

VARIABLE RESISTANCE

Variable resistors consist of a resistance track with connections at both ends and a wiper which moves along the track as you turn the spindle. The track may be made from carbon, cermet (ceramic and metal mixture) or a coil of wire (for low resistances). The track is usually rotary but straight track versions, usually called sliders, are also available.

Variable resistors are often called potentiometers in books and catalogues. They are specified by their maximum resistance, linear or logarithmic track, and their physical size. The standard spindle diameter is 6mm.

IR SENSORS

(GP2D12)

The GP2D12 sensor use triangulation and a small linear CCD array to compute the distance and/or presence of objects in the field of view.  The basic idea is this: a pulse of IR light is emitted by the emitter.  This light travels out in the field of view and either hits an object or just keeps on going.  In the case of no object, the light is never reflected and the reading shows no object.  If the light reflects off an object, it returns to the detector and creates a triangle between the point of reflection, the emitter, and the detector. 

        

The angles in this triangle vary based on the distance to the object.  The receiver portion of these new detectors is actually a precision lens that transmits the reflected light onto various portions of the enclosed linear CCD array based on the angle of the triangle described above.  The CCD array can then determine what angle the reflected light came back at and therefore, it can calculate the distance to the object. 

 

                 Sensing distance of GP2D12

 

CRYSTAL OSCILLATOR

(ML 11.0592)

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that can be configured for use as an on-chip oscillator, as shown in Figure below. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven, as shown in Figure below. There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.

 

 

    

 

 

 

    

 

Why Two 33pF capacitors are used with crystal oscillator in 89c52 microcontroller?

 

Usually, crystal is between two pins of the CPU, and two caps of 33 pF are mounted from these pins to the ground.
The purpose is to "dephase" the crystal signal to provide a lead/lag to the buffers inside the CPU and allows the oscillation! (The oscillator is a feed-back loop around a buffer: you need input/output OUT OF PHASE to maintain oscillation. The caps shift the phase, while the Xtal maintains the frequency).

 

VOLTAGE REGULATOR

(LM7805)

The LM78M05 , a three-terminal positive voltage regulators employ built-in current limiting, thermal shutdown, and safe-operating area protection which makes them virtually immune to damage from output overloads.

With adequate heatsinking, they can deliver in excess of 0.5A output current. Typical applications would include local (on-card) regulators which can eliminate the noise and degraded performance associated with single-point regulation.

Features   • Output current in excess of 0.5A • No external components • Internal thermal overload protection • Output voltages of 5V

 

OTHER COMPONENTS

 

RESISTORS

• 10 kΩ
  
• 8.2 kΩ
  
• 330 kΩ
  

 

CAPACITORS

• 10 µF
  
• 330 µF
  
• 0.1 µF
  
• 33 pF
  

 

DIODES

1N4007

                                                                  

 

 

 

IC BASE

• 40 pin
  
• 16 pin
  

  
   

 

 

 

 

 

 

 

VERO BOARD    

Stripboard is a widely-used type of electronics
prototyping board characterized by a 0.1 inch (2.54 mm) regular (rectangular) grid of holes, with wide parallel strips of copper cladding running in one direction all the way across one side of the board. It is usually known by the name Veroboard, which is a trademark, in the UK, of British company Vero Technologies Ltd, who invented this kind of board.

 

 

WIRE CONNECTORS

These connectors are used to connect wires through the vero board through which input , power supply or outputs are taken out through the board.

Different conectors used are:

• 8 pin
  
• 4 pin
  
• 2 pin
  

  
   

 

DC MOTOR (12V -50mA)

 

 

 

ROBOTIC WHEEL

 

Two types of wheel have been used:

• Main wheel(Front)
  
• Support wheel(Rear)
  

 

 

 

 

 

 

 

ROBOTIC BASE

It is made up of light weight material alumunium which provides easy movement of the robotic vehicle.It has folowing provision s in it:

• Slot for DC motors.
  
• Rear support wheel.
  
• Slot to clamp sensors.
  
• 9V battery holder.