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EOPD

The EOPD sensor uses light signals to detect the presence of an object or measure the distance to a target. This sensor is not a conventional light sensor and does not respond to external light sources. Instead it generates its own light source and responds only to the reflection of this internal light source. The EOPD automatically cancels background light so no calibration is necessary when moving from bright light conditions to low light.

The EOPD has two sensitivity settings, standard range and long range. In long range mode, the EOPD is about 4 times more sensitive than in standard range.

Display Settings

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  1. This number shows which NXT sensor port is selected to connect the EOPD. You can change this number in the configuration panel Port selection or by wiring a variable to the port plug on the drawer.

Configuring the EOPD Block

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  1. Choose the port your EOPD is plugged into. By default, the block will be set to port 1 for the EOPD. You can change this selection if you want.
  2. Use the slider to set the trigger value or type a value directly into the input box. Select the radio button to the right of the slider if you want the block to be triggered by levels higher than the trigger value; select the left radio button to trigger the block with levels lower than the trigger value. You can also use the pull-down menu to set the “true” portion of the slider.
  3. If you check the “Long Range” checkbox, the EOPD sensor will adjust the sensitivity to detect objects over a longer distance.

Configuring the EOPD Sensor block’s Data Hub

You can control the EOPD block dynamically by connecting data wires (from other blocks’ data hubs) to the EOPD block’s data hub.

Open a block’s data hub by clicking the tab at the lower left edge of the block after it has been placed on the work area.

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Data wires carrying input information to a block are connected to the plugs on the left side of its data hub. Data wires carrying output information are connected to the plugs on the right side.

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[A] Input plug
[B] Output plug
[C] Number data wire (yellow)
[D] Logic data wire (green)
[E] Text data wire (orange)
[F] Broken data wire (gray)

Passing data from the input plug to the output plug

If an input plug has a corresponding output plug (see A above), the input data will pass through from the input plug to the output plug without being changed. In this case, you can only use the output plug if the input plug is connected to an input data wire; connecting an output data wire to such an output plug without a connected input data wire will cause the output data wire to be “broken” (and colored gray).

Data wires carry specific types of data

Each data wire carries a specific type of data between blocks. For example, if a data wire is dragged from a logic plug on a block’s data hub, it can only be connected to a logic plug on another block’s data hub. The chart below shows what kind of data each plug can accept or send out.

Data wire colors

Data wires are identified with specific colors: wires carrying number data are colored yellow, wires carrying logic data are colored green, and wires carrying text data are colored orange.

“Broken” data wires

If you try to connect a data wire to a plug of the wrong data type, the data wire will be broken (and colored gray). You will not be able to download your program if a data wire is broken.

If you click a broken wire you can read why it is broken in the small help window in the lower right corner of the work area.

Data must be within the possible range of the plug

If an input data wire transmits a value outside the possible range of the plug it is connected to, the block will either ignore the value or change it to a value within its range. For plugs that allow just a few input values (example: just 0, 1, or 2), the plug will ignore the input if a value arrives outside its range.

EOPD block Data Hub plugs

You must click on the Data Hub to open it as shown.

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  1. This plug wires the NXT port number your EOPD is connected to.
  2. This plug wires the value to compare against for the trigger.
  3. This plug wires the logic used in the trigger comparison.
  4. This plug wires the Long Range selection.
  5. This plug wires the result of the trigger comparison.
  6. This plug wires the processed value from the sensor.
  7. This plug wires the raw value from the sensor.

Examples showing the logical result.

This chart shows the different characteristics of the plugs on the EOPD block's data hub:

Plug Data Type Possible Range What the Values Mean
Max/Min Port Number 1, 2, 3 or 4 NXT sensor port the EOPD is plugged into
trigger Trigger Point Number 0 - 1023 Value to compare against
greater or less Greater / Less Logic True/False

Logic used in comparison. True = Greater, False = Less

Yes/No Long Range Logic True/False Select Long Range Mode
True = Long Range, False = Standard Range
Max/Min Yes / No Logic True/False Result of comparison
result Result Number 0 - 100 Processed or scaled value read from sensor. * see note
Raw data Raw Value Number 0 - 1023 Raw (unscaled) value read from sensor

*Note: This value is derived from the square root of the raw value and can be divided into a constant to calculate distance to a target. The constant should be chosen to yield the distance in desired units. You can choose the units to suite each application. For example, divide 250 (the constant) by the processed value and the result will be a linear scale representing distance units to the target. If you change the constant to a larger number, say 350, the resulting scale will have more (smaller) units for a given distance.

For more information and example programs go to www.hitechnic.com