Phidgets

Phidgets let you avoid soldering and microcontroller programming so you can put together an installation pretty quickly. Good for prototyping.

• primarily supported in Windows, but also on Mac OS X, Linux
• USB devices, installation and re-configuration is "plug and play"
  
• support available from a number of programming environments:
• Visual Basic
• Visual Basic for Applications (VBA)
• C/C++ (available in Windows, Linux, MacOS)
• Borland Delphi
• Java (Windows, MacOS, Linux)
  
• etc
  

USB

• universal serial bus, i.e. lets you hang devices in any order
• use the phidget monitor to see what's successfully connected
• power issues: some phidgets will need separate power (6-12 V DC) in certain heavier-load conditions, others will simply take their power from USB
• you have to wait a bit more the first time you connect a new type of Phidget (or any other USB device for that matter) in a certain USB connector
• sometimes you will get an error the first time, try disconnecting and reconnecting the device, it may work without errors

8/8/8 "Phidget Interface Kit" (8 digital inputs, 8 digital outputs, 8 analog inputs; there exist boards of other sizes)

• we have 5 boards
• will need external power in some USB connectors
• will surely need external power when other phidgets are connected to the board. If you want to avoid this, connect the phidget directly to the computer or use a powered USB hub
• use the interface kit controller to monitor the Phidget Interface Kit
• 8 digital inputs (see page 5) , basically reading the state of a switch
• 8 digital outputs (see page 5)
  • basically turns a switch on and off
  • simple and frequent example: LEDs
  • a LED is a diode, will let current pass in only one direction
    
  • shorter pin to the ground (cathode), the longer one (anode) to the digital output
    
  • to avoid short, 300 Ohm resistor included in the phidget output
    
• 8 analog inputs (page 4)
• you can connect a number of packaged sensors
• example: room monitoring (presence, temperature)
• but any other sensor that can be fed with 5V and produce voltage between 0 and 5V will work. See details below.
• we have 3 sensors for each of: force, light, mini joystick, rotation, slider, temperature, touch
• besides these, we can also detect acceleration and presence of RFID tags (see specific phidgets below)
  
• we don't have at this time sensors for: current, humidity, magnetic, motion, multi-turn rotation, pressure, vibration, voltage
  
• always disconnect the USB to the computer before modifying the interface kit circuit! (attaching analog inputs, digital inputs or outputs)

• package Phidgets
  
• the main documentation is the source of the classes. Luckily it's very simple
• each phidget is represented by a class with the name like Phidget*.java
• the ones we use are the classes corresponding to the devices we have
• PhidgetInterfaceKit, PhidgetServo, PhidgetRFID, PhidgetAccelerometer
• important Phidget methods
• info: GetSerialNumber(), GetLibraryVersion(), GetDeviceVersion()
  
• useful when software and hardware evolve
  
• GetSerialNumber() identifies the device uniquely
  
• Open() looks for the physical USB device
• you can specify whether you want to open the device in exclusive mode
• you can specify the serial number of the device, in case there are more Phidget interface kits attached
  
• GetIsAttached() tells whether the device is still attached
  
• run()  monitors the sensors continuously and will only end when the device is disconnected
• this of course makes no sense for outputs/actuators like e.g. motors
  
• start() does run() in another thread
• so the main thread is left for other operations, like e.g. driving outputs
• the thread seems to be a daemon, i.e. if the program main() gets to the end, the thread dies!
• so you must have some sort of loop, or simply use run()
• Close() gives away resources needed by your program to access the device
• device-specific methods depend on the actual device function
• most devices let you register listeners that will have a method called when a device changes state
  

• we look at a Java example
  
• board size
  
• GetNumOutputs() the number of digital outputs (8 for our board)
• GetNumInputs() the number of digital inputs (8)
• GetNumSensors() the number of analog inputs (8)
• digital input reading: GetInputState(int index)
• digital output setting: SetOutputState(int index, boolean value)
• digital output reading: GetOutputState(int index)
  
• analog input reading
  
• GetSensorValue(int index) returns GetSensorRawValue(int index) processed according to:
• a normalization minimum:  GetSensorNormalizeMinium(int index), SetSensorNormalizeMinimum(int index, int value)
  
• a normalization maximum: GetSensorNormalizeMaximum(int index), SetSensorNormalizeMaximum(int index, int value)
• a change trigger: GetSensorChangeTrigger(int index), SetSensorChangeTrigger(int index, int value)
• event subscription:
• add_IPhidgetInterfaceKitEventsListener(_IPhidgetInterfaceKitEvents listener)
• remove_IPhidgetInterfaceKitEventsListener(_IPhidgetInterfaceKitEvents listener)
• a method of the listener will be invoked whenever something happens with an analog or digital input
• digital input change: OnInputChange(_IPhidgetInterfaceKitEvents_OnInputChangeEvent event)
• analog input change OnSensorChange(_IPhidgetInterfaceKitEvents_OnSensorChangeEvent event)
• the event object will give information on
• which input has changed: get_Index()
• what is the new value: get_SensorValue() for analog inputs, get_NewState() for digital inputs
  
• error: OnError(_IPhidgetInterfaceKitEvents_OnErrorEvent event)

• 4 servo motor driver
  • we have 3, and a large number of servo motors
    
  • can turn from -23 to 231 degrees, in fine-tuned angles
    
  • a simple servo slider
    • USB power only goes to motor 0. If you want to drive other servos, you need to give 6-12V DC power to the board
  • API (PhidgetServo)
  • GetNumMotors()
  • double GetMotorPosition(int index)
  • SetMotorPosition(int index, double angle)
  • Java example
    
  • initial position seems to be 0 but it's not always, always set it to the desired position initially
  • Beware of multiple Java programs running at the same time (esp in Eclipse)
  • other types of motors, see motor tutorial , advanced servo (can control e.g. rotation speed), DC motors, stepper motors (turn with a precise number of steps)
    
• text LCD
• 64 LEDs (can be controlled also as simple digital outputs)
• numeric LEDs

• RFID board
  • we have 3
  • detects when a certain tag is within 3 inches of the RFID receiver
    
  • a simple RFID test program
  • one tag can be present only. If more tags are present, one or none will be reported
    
  • API: (PhidgetRFID):
    
  • the latest RFID tag seen: String GetLastTag() 
    
  • you can register a callback method to be called whenever a tag comes around
  • add_IPhidgetRFIDEventsListener(_IPhidgetRFIDEvents listener)
  • the listener method called (besides OnError)
    
  • OnTag(_IPhidgetRFIDEvents_OnTagEvent event)
  • the event only contains the tag number: get_TagNumber()
  • the device also has some outputs, e.g. a LED
  • GetNumOutputs()
  • GetOutputState(int index)
  • SetOutputState(int index, boolean value)
    
  • Java example
    
  • issues
    
  • some older Phidget RFID receivers do not work with the USB hub of  the newer Phidget Interface Kits
  • connect them directly to a computer USB instead
    
• accelerometer
  • we have one
  • a simple accelerometer test program
  • API (PhidgetAccelerometer)
  • number of axes: GetNumAxis()
  • sensor value reading: double GetAcceleration(int axis)
  • change trigger for acceleration: SetAccelerationChangeTrigger(int axis, double value)
    
  • register callback: add_IPhidgetAccelerometerEventsListener(_IPhidgetAccelerometerEvents l)
  • listener method called: OnAccelerationChange(_IPhidgetAccelerometerEvents_OnAccelerationChangeEvent e)
  • the event contains information on the axis where acceleration changed (get_Index()) and the acceleration value (double get_Acceleration())
  • Java example
    
• temperature sensor with termocouple (-200, +1200 degrees)
• weight sensor

• hardware descriptions and some interesting sensors
• resistive and active sensors
  • resistive sensors are simply given a voltage to measure their resistance
  • some resistive sensors only have 2 pins and an extra resistance is needed
  • active sensors are given a voltage and will output a voltage proportional to what is measured
  • in all cases, analog-digital conversion takes place inside the phidget
• guide to connecting new kinds of sennsors to the phidget analog input cable

• do you want to drive bulbs?
• external supply
• large voltages
• a problem: common ground with the digital circuit,
• you can avoid this problem with optocouplers
• using relays: up to 240V
• using 16/16 phidget interface kit: up to 30V DC
• example: incandescent lights
• device examples: lamps, motors, vents, valves

• external power supply
• < 3 V = 0
• 4-30V = 1

• allow you to skip the PC if needed
• allow programming via a serial connection
  
• sensors/outputs are connected to microcontroller pins, via specific circuits
  
• Basic stamp programmed in BASIC
  
• PIC programmed in C
  
• multithreading: since you read more sensors at a time, it is important that your microcontroller allows for multiple programming (multithreading). Early Basic Stamps didn't do this