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Thread: Position Detection DT40 and datasheets

  1. #1
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    Default Position Detection DT40 and datasheets

    Hello everyone! I have 2 old DT40 worked galvoscanners and digital Oscilloscope. Can some one help me? I really don't understand how I can read data from postion detector. And if it possible, I need a datasheet with maximum number of characteristics for this scanners. Thx everyone who can help. Sorry for my bad English.
    Last edited by LexAndersen; 02-24-2015 at 21:55.

  2. #2
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    This is a optical position sensor with an array of photodiodes and a source LED.

    You understand that in a proper Galvo amp, Sensor linearity is corrected by adding position feedback signals to the LED current in a controlled manner, yes?

    Ia and Ib are the photocurrents from the position detector photodiodes. Note the need for 1% resistors in most parts of the detector circuits.

    The first drawing is the position demodulator difference amp. The second drawing is the Position Detector LED supply with Automatic Gain Control for the Linearity Correction.

    Note that Va and Vb from the demodulator are tied to the Va and Vb inputs on the AGC schematic.

    R13, Position Linearity sets the current in the position detector LED.

    The third drawing shows the LED and Photodiodes in the galvo.

    The schematics shown are from a generic galvo amp.

    As far as I know there is no such thing as a DT40 Data Sheet beyond what is on the DT web site.

    Amplifiers are very inexpensive. Why you would want to build them, I cannot understand.

    Steve
    Attached Thumbnails Attached Thumbnails PositDetectGalvo.png  

    AGCPOSITGALVO1.png  

    INGalvoPOSIT.png  

    Last edited by mixedgas; 02-25-2015 at 13:02.
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    Hello. I want to clarify. I have DT40 scanner and driver. For exaple I give to driver step voltage (+5V, -5V) and want to detect position scanner on time. What scheme I need to connect galvo scanner for position detection. Click image for larger version. 

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  4. #4
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    See test point 1 in my first diagram, You need to find the corresponding TP on your board.

    One TP is next to a 0.1 Ohm Resistor, that is the Galvo Current. Another TP will be the position sensor output.

    I cant see the bottom of the board, so I can't help you further.

    Steve
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