ENC1000 User Guide

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Revision as of 16:37, 8 June 2017 by Jdecoux (Talk | contribs) (Calculating Velocity)

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ENC1000 Functional.jpeg

Required Hardware

Connecting the Pieces

  1. Connect the ENC1000 to the VINT Hub using the Phidget cable.
  2. Connect the encoder to the Phidget using an encoder cable.
  3. Connect the VINT Hub to your computer using a USB cable.


Testing Using Windows

Phidget Control Panel

In order to demonstrate the functionality of the ENC1000, the Phidget Control Panel running on a Windows machine will be used.


The Phidget Control Panel is available for use on both macOS and Windows machines.

Windows

To open the Phidget Control Panel on Windows, find the Ph.jpg icon in the taskbar. If it is not there, open up the start menu and search for Phidget Control Panel

Windows PhidgetTaskbar.PNG

macOS

To open the Phidget Control Panel on macOS, open Finder and navigate to the Phidget Control Panel in the Applications list. Double click on the Ph.jpg icon to bring up the Phidget Control Panel.


For more information, take a look at the getting started guide for your operating system:


Linux users can follow the getting started with Linux guide and continue reading here for more information about the ENC1000.

First Look

After plugging the ENC1000 into your computer and opening the Phidget Control Panel, you will see something like this:

ENC1000 Panel.jpg


The Phidget Control Panel will list all connected Phidgets and associated objects, as well as the following information:

  • Serial number: allows you to differentiate between similar Phidgets.
  • Channel: allows you to differentiate between similar objects on a Phidget.
  • Version number: corresponds to the firmware version your Phidget is running. If your Phidget is listed in red, your firmware is out of date. Update the firmware by double-clicking the entry.


The Phidget Control Panel can also be used to test your device. Double-clicking on an object will open an example.

Encoder

[[Image:{{{1}}}_Encoder_IntervalIOMode_Example.jpg|right|link=]]

When you double click on an Encoder object, a window like the one pictured will open.

  • At the top of the window, information about your device and the properties of this particular channel will be listed.
  • On the left, change trigger and/or data interval can be changed. For more information on these settings, see the Data Rate/Change Trigger page. You can enable the input (if applicable) and specify the counts per revolution (CPR) to enable velocity calculation. Press enter after typing a number to enable velocity. You can also change the IO mode of the encoder to enable pull-up or pull-down resistors on the encoder input if necessary.
  • On the right, real-time data is displayed:
    • Position Change: The number of ticks (or quadrature cycles) that have occurred since the last change event.
    • Time Change: The amount of time in milliseconds that has elapsed since the last change event.
    • Position: The total position in ticks relative to where the encoder was when the window was opened.
    • Index Position: The position where the index channel (if supported by this encoder) was last encountered.
    • Velocity: If a CPR has been specified, the average velocity in rotations per minute.


Testing Using Mac OS X

  1. Go to the Quick Downloads section on the Mac OS X page.
  2. Download and run the Phidget OS X Installer
  3. Click on System Preferences >> Phidgets (under Other) to activate the Preference Pane
  4. Make sure your device is properly attached
  5. Double click on your device's objects in the listing to open them. The Preference Pane and examples will function very similarly to the ones described above in the Windows section.

Testing Using Linux

For a general step-by-step guide on getting Phidgets running on Linux, see the Linux page.

Using a Remote OS

We recommend testing your Phidget on a desktop OS before moving on to remote OS. Once you've tested your Phidget, you can go to the PhidgetSBC, or iOS pages to learn how to proceed.

Technical Details

The ENC1000 can be used with a wide assortment of mechanical and optical encoders. The encoder should be of incremental quadrature output type, indicating that there will be two output channels (usually labeled A and B).

The maximum rate of the ENC1000 is specified at 100,000 quadrature cycles per second. In your application, this number relates directly to the number of revolutions per second you wish to measure, and the number of counts per revolution specified for your encoder. If your encoder's wheel has 1000 cycles per revolution, then the limit on measurable revolutions per second is 100, or 6,000rpm.

Connector

The encoder input on the ENC1000 uses a 5-pin, 0.100 inch pitch locking connector. The connectors are commonly available - refer to the Table below for manufacturer part numbers.


Manufacturer Part Number Description
Molex 50-57-9405 5 Position Cable Connector
Molex 16-02-0102 Wire Crimp Insert for Cable Connector
Molex 70543-0004 5 Position Vertical PCB Connector
Molex 70553-0004 5 Position Right-Angle PCB Connector (Gold)
Molex 70553-0039 5 Position Right-Angle PCB Connector (Tin)
Molex 15-91-2055 5 Position Right-Angle PCB Connector - Surface Mount


Note: Most of the above components can be bought at Digikey.


  • If encoder needs resistor on power line to limit current, the user needs to solder it on to the cable

Calculating Velocity

When your program captures an encoder change event, it'll receive two variables: positionChange (measured in 'ticks', four of which equal one quadrature count for the ENC1000) and timeChange (measured in nanoseconds). You can use these values to easily compute the instantaneous velocity of the encoder. For example, our C# example code implements this method of velocity calculation:


void enc_change(object sender, Phidget22.Events.EncoderEncoderChangeEventArgs e) {

...

// Convert time change from milliseconds to minutes
double timeChangeMinutes = e.TimeChange / 60000.0;
// Calculate RPM based on the positionChange, timeChange, and encoder CPR (specified by the user)
rpmTxt.Text = (((double)e.PositionChange / CPR) / timeChangeMinutes).ToString("F0");

...

}


This implementation may be useful if you're graphing the RPM on a line graph, but if it's being used to display the current RPM as a single number, it won't be very helpful because when the motor changes speed or direction frequently, it'll be hard to read the velocity as a meaningful value. This method can also be prone to variations in velocity if the encoder's CPR is low and the sampling rate is high. To solve these problems, you should decide on a time interval during which you'll gather data, and take a moving velocity calculation based on that data. You can use the Queue data type to make this easy:


Queue<double> positionChangeQueue = new Queue<double>();
Queue<double> timeChangeQueue = new Queue<double>();

void enc_change(object sender, Phidget22.Events.EncoderEncoderChangeEventArgs e) {

double totalPosition = 0;
double totalTime = 0;
int n = 500; // sampling window size, duration is 500*n where n is the data rate of the ENC1000

// add the newest sample to the queue
positionChangeQueue.Enqueue(e.PositionChange);
timeChangeQueue.Enqueue(e.TimeChange);

// If we've exceeded our desired window size, remove the oldest element from the queue
if ( positionChangeQueue.Count >= n ) {
     positionChangeQueue.Dequeue();
     timeChangeQueue.Dequeue();
}

// Calculate totals for position and time
foreach( double positionChange in positionChangeQueue ) {

     totalPosition += positionChange;
}

foreach( double timeChange in timeChangeQueue ) {

     totalTime += timeChange;
}

// Convert time change from nanoseconds to minutes
double timeChangeMinutes = totalTime / 660000000000.0;
// Convert quadrature edges into encoder counts
double positionChangeCounts = totalPosition / 4;
// Calculate RPM based on the positionChange, timeChange, and encoder CPR (specified by the user)
double rpm = (positionChangeCounts / timeChangeMinutes / CPR);

}


What to do Next

  • Programming Languages - Find your preferred programming language here and learn how to write your own code with Phidgets!
  • Phidget Programming Basics - Once you have set up Phidgets to work with your programming environment, we recommend you read our page on to learn the fundamentals of programming with Phidgets.