-Daryl

= = = = = = =1. Collision Sensors=

toc The functionality of a collision sensor can be found in various types of sensors like force sensors, proximity sensors, distance sensors, IR sensors, and range finders. However, not all of them may be suitable for our robotic arm project.

The following are the requirements that need to be considered:
 * Requirement for Selection**

1. Range distance - the range distance must be reasonable enough, low "minimum sensing distance" and reasonable "maximum sensing distance" 2. Connection - information regarding connecting and programming the sensor must be sufficient. 3. Price - reasonable price

Force sensors should not be used in our project for they only detect collisions as it happen and not prior. Proximity sensors also tend to be more specific on the object's characteristics (eg plastic or metal). Most contact and proximity sensors are only used to detect human fingers. Distance sensors seem to be advantageous because they can output a voltage reading based on the distance of the object. This reading can be converted to distance by means of scaling and proportion. The problem however is that most distance sensors have a very high sensing range (eg. 4" - 30"). A lower "minimum sensing distance" is needed. On the contrary, most Infra red sensors either have a very small "maximum sensing distance (eg. maximum of 6 mm) or a high judgment distance (eg. 40cm). The last option are range finders, which tend to offer more options depending on the distance range that is needed. Taking into account all the requirements for selection, the Devantech Ultrasonic Range Finder SRF05 is best suited for our design project. - Determines the distance of an obstacle within sonar field of view - LED status indicator blinks when sonar fires - Use to control servo motors based on an obstacle's distance - Can use only a single pin for both trigger and echo
 * Choosing the Right One**
 * Devantech Ultrasonic Range Finder SRF05**
 * Features**

Length: 43mm Width: 20mm Height: 17mm Resolution: 3-4cm Range Distance: 1cm to 4m Interface: Positive TTL level signal, width proportional to range Power requirements: 5V and 4mA Frequency: 40KHz Trigger pulse: At least 10us
 * Specifications**

The SRF05 has two modes of operation.
 * How it Works**

This mode uses separate trigger and echo pins. To work on this mode, the Mode pin is left unconnected.
 * Mode 1 - Separate Trigger and Echo**



This mode uses a single pin for both trigger and echo signals, therefore, saving valuable pins on microcontrollers. To work on this mode, the Mode pin is connected to the 0v Ground pin. The SRF05 will wait 700uS after the end of the trigger signal before raising the echo line. This wait time should be enough to ready the measuring code and switch the function of the pin into echo.
 * Mode 2 - Single pin for both Trigger and Echo**

**Calculating the Distance** A 10us pulse is supplied to the trigger input to start ranging. The SRF05 will send out an 8 cycle burst of ultrasound at 40KHz (at the speed of sound) and the echo line is raised to high. After sending out the sonar, the SRF05 listens for an echo and as soon as it detects one, it lowers the echo line. The echo line is a pulse whose width is proportional to the distance of the object from the sensor. If nothing is detected after 30ms, the echo line is lowered.

Since the echo pulse is proportional to distance, we can determine the distance of the object. Considering the width of the pulse is measured in us, then dividing by 58 will give the distance in cm, or dividing by 148 will give the distance in inches.

The time in between triggers must be 50ms. This is to make sure that the previous emitted sonar will not overlap with the next one.

The other 5 pins on the opposite side of the SRF05 are not to be used or connected. They were used only once during manufacturing to program the flash memory on the PIC16F630 chip.

The SRF05 sensor will be placed on important locations of the robotic arm. An object detection by one or more of the sensors will translate to a restrictive movement on the respective joints of the robotic arms (both user and output side).
 * Beam Pattern**
 * Integration**

=2. Motion Sensor: Gripper=
 * (open and close movement - user side) **


 * One-Directional Flex Sensors - FLX-03**

• A type of motion sensor that detects the bending orientation of a device • Flexible and bendable material • Lightweight
 * Features**

Thickness: 0.19" Length: 4.5" Width: 0.25" Connector: 2-pin male Resistance Range: 10 kΩ - 40kΩ
 * Specifications**

A one directional flex sensor is a unique component that changes resistance when bent in a certain direction. In case of the image above, bending is outward the screen. When the sensor is unflexed, the resistance reading on both pins will be approximately 10 kΩ. As the flex sensor is bent, the resistance gradually increases to a maximum of 40kΩ. A table must be completed to test the precision of the FLX-03 Flex Sensor. Resistances are to be measured with respect to the sensor's degree of bending. If the device is working correctly, the plot of resistance vs flex angle should be linear and should show an increasing slope of a straight line. Note: A reference angle of 0 degrees may be used for the unflexed position.
 * How It Works**
 * Testing the Sensor**

The flex sensor is suggested to be placed inside the gripper. As the gripper closes and opens, the flex sensor, which is located inside, should also bend consequently. The sensor then is to be integrated into a flex sensor circuit shown below to convert input signal into a proper engineering unit (voltage). Basic flex sensor circuit • Op-amp power set to 5V for the positive pin and 0V for the negative pin • Input voltage Vin is set to 5 volts • Resistance R2 is set to 33kΩ • Taking into account the maximum and minimum flex sensor resistance R1, Vout can be calculated • Vout will be in the range from 2.8V to 4V.
 * Integration**

=3. Motion Sensor: Robotic Arm=
 * (arm movements - user side) **

** • Measures gravitational force of ±  3g on three axis (X, Y, Z) • Onboard regulator to provide 3.3-volt power • Contains a four channel, 12-bit analog to digital converter to read the H48C voltage outputs. • Small and breadboard friendly package
 * Hitachi H48C Tri-Axis Accelerometer Module
 * Features**

• Power requirements: 5 VDC • Communication: Serial SPI • Length: 0.8" • Width: 0.7" • Thickness: 0.45"
 * Specifications**

The Hitachi H48C tri-axis accelerometer module detects tilt, rotation, and acceleration of a specific object that it is attached to. Its initial function is to measure ±  3g on all axis. To get velocity and displacement of the sensor, integration is needed. In this project, displacement shall be of importance so the output signal of the accelerometer needs to be double integrated. For free fall, output indicates simultaneous 0g on all axis. (more details on pin assignments and functions to be added soon)
 * How It Works**

A total of three H48C accelerometers shall be used. One on each arm of the robot (user side) will be placed and will be responsible for sensing the position of the arm they are attached to. This will translate to the movement of its robotic arm (output side) counterpart. Arm displacements are all relative to the base of the input robotic arm.
 * Integration**

=4. Motion Sensor: Base Rotary Motion= ** • A sensor that detects rotation • ±  300  °  /s full scale • SPI interface • Power requirements: 5VDC @ 5.25 mA  • Maximum angle of rotation: 300  ° • Length: 0.75" • Width: 0.69" • Thickness: 0.47"
 * (base rotation - user side)
 * LISY300 Gyroscope Module**
 * Features**
 * Specifications **


 * How It Works



(more details on pin assignments and functions to be added soon)

Testing the Sensor** (Instructions available from manufacturer)

The LISY300 Gyroscope Module shall be used to measure the base rotation of the robot (user side). This will then translate to the rotary motion of the robot's base (output side).
 * Integration**