WEEK 12 (11 - 15 Oct 2010)

RC Servos Motor

A "servo" is a generic term used for an automatic control system. It comes from the Latin word "servus" - slave. In practical terms, that means a mechanism that you can set and forget, and which adjusts itself during continued operation through feedback. The word "servo" really means an RC (remote control) servo motor. This is a small box designed for use in hobby airplanes and cars. Inside this box is a complete servo system including: motor, gearbox, feedback device (pot), servo control circuitry, and drive circuit. RC servos normally have 3 wires: +v, ground, control. The control signal is a pulse that occurs at about 50 Hz. The width of the pulse determines the position of the servo motors output. This would be easy to control with a digital controller such as a Basic Stamp. Most will run on 5-6 volts and draw 100-500ma depending on size. The control circuitry to perform good servo of a DC motor is much more complex than the circuitry that controls a stepper motor.

 RC servo controlling

Servo motors are small, compact and quite cheap. The servo motors itself have built in motor, gearbox, position feedback mechanism and controlling electronics. The servo motor can be controlled to move any position just by using simple pulse controlling. 

Figure 2.4: The rotation of servo motor

Servo motors have three wire interfaces for controlling and power supplying. The wires are colored using following color code:

Ø  BLACK     Ground

Ø  WHITE     Control pin

Ø  RED       +4.8V power supply (+5V works well in this)

Controlling of the servo motors is used using pulse controlling. The control pulse is positive going pulse with length of 1 to 2 ms which is repeated about 50-60 times a second. The details can be check in the figure below:

                         ____                               ____      _+4.8V

                        |    |                             |    |                  

                        |    |                             |    |

                    ____|    |_____________________________|    |____  _GND

                        |<-->|

                        1.2 ms

                               |<-------------------------------->|

                                      18-25 ms

Sending 1 ms pulses sets the servo to one end position and sending 2 ms pulses sets it to the other end position. Sending 1.5 ms pulse sets the servo motor to the center position. The controlling scheme is very easy to implement with some electronics.  

RC servos are hobbyist remote control devices servos typically employed in radio-controlled models, where to provide actuation for various mechanical systems such as the steering of a car, the flaps on a plane, or the rudder of a boat.

                                                                                               

Figure 2.6: Small R/C servo mechanism
1.Electric motor
2.Position feedback potentiometer
3.Reduction gear
4. Actuator arm

 RC servos are composed of a DC motor mechanically linked to a potentiometer. Pulse-width modulation (PWM) signals sent to the servo are translated into position commands by electronics inside the servo. When the servo is commanded to rotate, the DC motor is powered until the potentiometer reaches the value corresponding to the commanded position. The servo is controlled by three wires: ground (usually black/orange), power (red) and control (brown/other color). This wiring sequence is not true for all servos, for example the S03NXF Std.

Servo is wired as brown (negative), red (positive) and orange (signal). The servo will move based on the pulses sent over the control wire, which set the angle of the actuator arm. The servo expects a pulse every 20 ms in order to gain correct information about the angle. The width of the servo pulse dictates the range of the servo's angular motion.

 

2.4.1    Driving RC servos

As has already been mentioned, all RC servos have three connections: power (positive), power (ground or negative), and the controlling signal. The interesting part is the control signal. An RC servo motor doesn't just run when we give it power. It's an intelligent device, and we must tell it what we want it to do. We need something that drives the servo with that control signal.

2.4.2    Powering RC Servos

Most servos require a power supply between 4.8V and 6.0V. The higher the voltage, the faster the servo will move and the more torque it will have.

2.4.3    Theory of Driving RC servos

The servo is controlled by a series of pulses, wherein the length of the pulse indicates the position to take.

pulse width	angle	comment
0.6m Sec	-45 degrees	minimum pulse length
1.5m Sec	0 degrees	center position
2.4 mSec	-45 degrees	maximum pulse length

Table 2.1

Increasing the pulse width by 10 µSec results in about a degree of movement on the output shaft.

·         These numbers are nominal, and vary slightly between manufacturers and models. The rate at which these pulses are sent isn't terribly important - only the width of the pulse.

So, the short story is, if we can make a series of electrical pulses, we can rotate the servo shaft through a range of 90 degrees. And that 90 degree range of rotation can open and close the jaw of a skull, move eyeballs left and right, point a finger, or do all sorts of creepy animation.

WEEK 11 (4 - 8 Oct 2010)

Continues design circuit diagram in the Proteus software, code test PCB input and output.

1. To design the suitable component in the Proteus.
2. To simulate the design in the Proteus.
3. To test code input and output.

WEEK 10 (27 sept - 1 Oct 2010)

Design Circuit Diagram in Proteus, Select proper input/output, Code test input/output and test PCB

This is a first design in the Proteus software. the design is not complete because in the library not have a distance sensor as a input. This design use micro-controller PIC 16f84A as a main controller in the systems. Two motor will use for movement the robot or as a output. Distance sensor as a input to detect the object in front of.

Servo Motor as a output for movement are selected. This servo motor able to control the position of the motor. The specification of this motor are suitable for the design of the robot. Two servo motor will used.

    Specification of servo motor

    - C36S=C36R
    - Speed (sec/60deg): 0.16/4.8V, 0.14/6.0V
    - Torque (Kg-cm): 3.5/4.8V, 4.5/6.0V (Maximum 6.0V)
    - Size (mm): 40.8x20.18x36.5
    - pulse width  range: 0.546ms to 2.4ms (estimation)
    - Weight (g): 36
    - Designed for "closed feedback".
    - Able to control the position of the motor

 

 
 

WEEK 9 (20 - 24 Sept 2010)

1. Triangular Sensor

Triangulation sensor

Optical Triangulation Sensors are commonly used to provide door mounted safety detection on swinging automatic doors.

These types of sensors are very common and manufactured in very high volumes. When automatic swinging doors open and close, it is important that they do not come into contact with pedestrians passing through the door.

Sensors used in the automatic door industry typically fall into four categories:

1. Microwave Sensors used to detect motion of a person as they approach an automatic door,
2. Reflective Optical Sensors that are mounted on the door header and detect the presence of a person in the door path
3. Camera based sensors that are also mounted on the door header and detect presence (a competing technology to Reflective Optical Sensors); and
4. Triangulation sensors which are mounted on the door and move with the door to provide safety.

Reflective and Camera technologies do not perform well on moving swing doors, because they typically depend upon detection of changes in the background. A sensor mounted on a swing door system is constantly in motion, so the background (i.e. floor beneath the door) changes continuously. To overcome this problem, a triangulation sensor provides an innovative solution.

2. Infra Red Sensor

 Infrared Sensor

 An infrared sensor is an electronic device that emits and/or detects infrared radiation in order to sense some aspect of its surroundings. Infrared sensors can measure the heat of an object, as well as detect motion. Many of these types of sensors only measure infrared radiation, rather than emitting it, and thus are known as passive infrared (PIR) sensors. 

Honeywell infrared detectors control or generate an electric current when irradiated. These metal or plastic products are available in a variety of electro-optical characteristics, package styles and mounting configurations. Often used with a corresponding emitter.

Best Used For:
Applications requiring object presence and limit sensing, position encoding, movement detection and counting. 

3. Ultrasonic Sensor

 
 

Ultrasonic sensors (also known as tranceivers when they both send and receive) work on a principle similar to radar or sonar which evaluate attributes of a target by interpreting the echoes from radio or sound waves respectively. Ultrasonic sensors generate high frequency sound waves and evaluate the echo which is received back by the sensor. Sensors calculate the time interval between sending the signal and receiving the echo to determine the distance to an object. 

Ultrasonic Sensor Compact Ultrasonic Sensor suitable for dual use, with high-performance characteristics. Standard operating frequency and good sensitivity. Ideal for use in range measurements, robot applications, alarm sensors, etc.
Part Code: US1240
Features • Excellent Directivity and Sensitivity • Detection Range: Up to 12m • Nominal Frequency: 40kHz • Operating Temperature: -30oC to +85oC • Dimensions: 12mm Diameter, 10mm High excluding pins, Pins - 5mm High

WEEK 8 (5 - 10 Sept 2010)

Research about Motor.

- to find the suitable motor for use in this robot.
- to get a speed motor

DC motor

A direct current (DC) motor is a fairly simple electric motor that uses electricity and a magnetic field to produce torque, which turns the motor. At its most simple, a DC motor requires two magnets of opposite polarity and an electric coil, which acts as an electromagnet. The repellent and attractive electromagnetic forces of the magnets provide the torque that causes the DC motor to turn.


Stepper Motor

 
Features of our hybrid stepper motor include:
1. Precise Position Control, linear Speed Selection, forward & Reverse, Pause and Holding Function, long life
2. Low Vibration, Low Noise, low cost, High Speed, High Torque, High Performance, low inertia and high accuracy
3. the variety of accessories and equipment, to meet the customers in different field
4. Most of motors are made as NEMA 8, NEMA 11, NEMA 14, NEMA16, NEMA 17, NEMA17, NEMA23, NEMA24, NEMA34, NEMA 43

Servo Motor

 

    - C36S=C36R
    - Speed (sec/60deg): 0.16/4.8V, 0.14/6.0V
    - Torque (Kg-cm): 3.5/4.8V, 4.5/6.0V (Maximum 6.0V)
    - Size (mm): 40.8x20.18x36.5
    - pulse width  range: 0.546ms to 2.4ms (estimation)
    - Weight (g): 36
    - Designed for "closed feedback".
    - Able to control the position of the motor

Digital Servo

Digital Servo is controlled by a built-in microcontroller unit with sophisticated control algorithm and this will result in several advantages over the conventional standard servo such as:

• Faster respond time
• Higher torque
• Higher precision

Specification:

• Origin: Taiwan
• Plastic Gear with Ball Bearing
• Standard size servo: 40.7mm x 20mm x 37mm
• Torque: 4.1kg.cm
• Speed: 0.17 sec / 60 Degrees
• Weight: 41g
• Maximum Movement Angle: 180 degrees
• Operating Voltage: 4.5V - 6.0V
• C/W Plastic Servo Horn

WEEK 7 (30 August - 3 Sept 2010)

Find the Circuit

Circuit Sensor

This circuit use NE555 timer.

• LOW TURN OFF TIME
• MAXIMUM OPERATING FREQUENCY GREATER THAN 500kHz
• TIMING FROMMICROSECONDS TO HOURS
• OPERATES IN BOTH AS TABLE AND MONO STABLE  MODES
• HIGH OUTPUT CURRENT CAN SOURCE OR SINK 200mA
• ADJUSTABLE DUTY CYCLE
• TTL COMPATIBLE
• TEMPERATURE STABILITY OF 0.005% PER  oC

DESCRIPTION

TheNE555 monolithic timing circuit is a highly stable controller capable of producing accurate time delays or oscillation. In the time delay mode of operation, the time is precisely controlled by one external reistor and capacitor.For as table operation as an osillator, the free running frequency and the duty cycle are both accurately controlled with two external resistors and one capacitor.The circuit may be triggered and reset on falling waveforms, and the output structure can source or sink up to 200mA. The NE555 is available in plastic and ceramic minidip package and in a 8-lead micro package and in metal can package version.

WEEK 6

Research Microcontroller Circuit and Foward Reverse Circuit

 

circuit PIC16f84A

• Only 35 single word instructions to learn

• All instructions single cycle except for program
branches which are two-cycle
• Operating speed: DC - 10 MHz clock input
                             DC - 400 ns instruction cycle

-Tthis microcontroller have 18 pin.

Circuit PIC16f877A

• Only 35 single-word instructions to learn
• All single-cycle instructions except for program branches, which are two-cycle
• Operating speed: DC – 20 MHz clock input
                             DC – 200 ns instruction cycle
• Up to 8K x 14 words of Flash Program Memory, Up to 368 x 8 bytes of Data Memory (RAM),  Up to 256 x 8 bytes of EEPROM Data Memory
• Pinout compatible to other 28-pin or 40/44-pin PIC16CXXX and PIC16FXXX microcontrollers

 

Motor Driven Circuit

• OPERATINGSUPPLY VOLTAGEUP TO 46 V

• TOTAL DC CURRENT UP TO 4 A

• LOWSATURATION VOLTAGE

• OVERTEMPERATURE PROTECTION

• LOGICAL ”0” INPUT VOLTAGE UP TO 1.5 V(HIGHNOISE IMMUNITY)

The L298 is an integrated monolithic circuit in a 15-lead Multiwatt and PowerSO20 packages. It is a high voltage, high current dual full-bridge driver designed to acceptstandardTTL logic levels and drive inductive loads such as relays, solenoids, DC and stepping motors. Two enable inputs are provided to enable or disable the device independently of the input signals. The emitters of the lower transistors of each bridge are connected together and the corresponding external terminal can be used for the connection of an external sensing resistor.An additional supply input is provided so that the logic works at a lower voltage.