FAQ for the Feasa LED Analyser

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Q. What Types of LED's and Colours can be tested ?

A. Many types of LED can be tested ranging in colour from Blue through to Red and
even Infra Red. All shapes and size of LED can be tested including Bi-Colour,
Tri-Colour, LED Displays and Bargraph Displays. The only requirement is to
position the end of the optical fiber near the illuminated LED.

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Q. Can the unit Test Infra-Red LED's and Reflective Optical Switches ?

A. Yes, Infra-Red LED's and Reflective Optical Switches can be tested to indicate
whether they are on or off. The wavelength or colour cannot be determined however.
The unit will detect Infra-Red up to approximately 1000nm wavelength.

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Q. Can Flashing or Blinking LED's be Tested ?

A. Yes, Flashing and Blinking LED's can be tested.

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Q. Can 7-Segment Display's be tested ?

A. Yes, each segment can be treated as a single LED by positioning the fiber end in front
of it. Even displayed numbers such as 0, 1 ..9 +,- can be verified and read back through
the Analyser. This can be very useful in a closed loop system where the requirement is
to verify a display reading.

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Q. Can Tri-Colour LED's be tested ?

A. Yes, each colour should be turned on individually and its RGB or HUE value read back.

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Q. Can Bargraph Displays be tested ?

A. Yes, Bargraph Display's can be tested. If a fiber is placed over each segment of the
Display then it's colour and intensity can be measured.

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Q. Can all LED's be tested simultaneously ?

A. Yes, each LED Analyser can measure up to 20 LED's simultaneously.

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Q. What Output Formats are available from the Unit ?

A. The Analyser can output results through the Serial port or through the Parallel port.
The RGB value, HUE value and Intensity of each LED is output.

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Q. How much time does it take to test 20 LED's.

A. 0.8 Seconds.

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Q. What is RGB ?

A. RGB stands for Red Green Blue. Each colour is split into the three primary colours and
these values are output from the Analyser.

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Q. What is HUE ?

A. HUE (HSI = HUE Saturation and Intensity). HUE is a value from 0 to 360 degrees and is
another way of representing the RGB values as a single number.
Pure Red is 0, Pure Green is 120 and Pure Blue is 240.
Amber which is a combination of Red and Green with a small amount of Blue is
around 40 to 50. Orange is around 20 and Bright Yellow is around 65.

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Q. How is the unit mounted in a Fixture ?

A. There are four mounting holes on the unit which can be used to attach the Analyser
to a Base Plate.

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Q. What options are available to connect the unit to a PC ?

A. The LED Analyser can be connected to the Serial port of a PC. A Serial cable is
provided with the unit.

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Q. How close to the LED should the fiber be mounted ?

A. 2mm is usually best. However, for bright LED's greater distances may be required.

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Q. What is the minimum bend radius for the fiber ?

A. The minimum bend radius recommended by the manufacturer is 15mm (0.6 Inches). Sharper bends can be tolerated but the loss will start to increase in the fiber.

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Q. How long can the fiber be in length ?

A. The fiber length can be extended if required. We currently have the length set to 0.5m
or 20inches approximately. The only issue is the amount of loss you can tolerate in the
fiber. The longer the fiber the greater the loss. For example, in a 30m (49 feet) length
of this fiber there will be a 3dB (50%) loss. If the LED being tested is bright then higher
losses can be tolerated and still be able to measure color. If Intensity is being measured
then the fiber loss must be taken into account.

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Q. What are the power requirements ?

A. 5-7V DC 200mA.

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Q.. What does an output of 255 255 255 mean ?

A. Unit is over range. This is caused by the LED being too bright or the fiber is
too close to the LED. Decreasing the the intensity of the LED will not affect the
colour being measured.

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Q. Why does a red LED which looks the same brightness as a green LED measure much
higher intensity ?

A. The Human Eye is less sensitive to red light so a Red LED can be brighter than it looks!

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Q. What is the format of the serial protocol ?

A. The serial protocol used to communicate with the LED analyser is very simple. A Terminal emulator such as Hyper Terminal can be used to demonstrate the communication with the LED Analyser. Hyper Terminal can be opened with the correct configuration settings using the Hyper Terminal icon at Start ->Programs -> Led Analyser Utilities ->LED Analyser Hyper Terminal. The same commands can be used from any programming language.

The settings are as follows RS232 57600 baud 8 Data bits, 1 Stop bit, No Parity, No Flow Control
Note: All commands are case sensitive (all upper case)

- Send SNE to the Led Analyser to trigger data capture. The system responds with S

- Send SPxxE to retrieve RGB data for LED xx (01 = fiber 1, 02 = fiber 2 etc.).
Analyser responds with SPrrrgggbbbiiiiiE where
rrr is RED value
ggg is GREEN value
bbb is BLUE value
iiiii is INTENSITY value

- Send SHxxE to retrieve Hue data for LED xx (01 = fiber 1, 02 = fiber 2 etc.).
Analyser responds with SHhhhhhE where
hhhhh is the hue value

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