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Blackbox PWM Specs / Compatibility

Discussion in 'Controller Boards' started by Lerronious, Oct 25, 2019.

  1. Lerronious

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    I'm trying to determine if I need to add a low-pass filter to the Blackbox PWM output typically used to control laser intensity. Looking through the specs for the accessory I find this:

    Program from 0 to 100% of rated output via a 0 to +5 volt, DAC-compatible, high-impedance programming input voltage.

    Also from the spec sheet, program current <100uA and <250msec response time (FULL LOAD, FULL-SCALE RESPONSE)

    Anyone care to weigh in on this esoteric application? Any help appreciated.
     
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    The real question is what PWM is accepted by your laser. (datasheet, or documentation)

    BlackBox runs on Grbl, so the default frequency is 1Khz
     
  3. Lerronious

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    Thank for the quick response and info regarding the grbl PWM freq.

    I could only find the "0 to +5 volt, DAC-compatible, high-impedance programming input voltage" statement in the product sheet. How do lasers handle the PWM input?

    Not being an EE and this being an oddball application, I cannot determine what conditions would require a DAC or low-pass filter. I was just going to hook it up and turn it on until I read "DAC-compatible input voltage" line in fine print.
     
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    What kind of laser is it :) any link, picture, is it a CO2 laser etc :) Hard to give you info without knowing what you want to connect (;
     
  5. Lerronious

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    It's a DC-DC High Voltage Converter. Takes a 12VDC input and and delivers a 0-5KV based on the 0-5VDC program input. I attached the spec sheet. The "detailed" product description is on page 3. And again, thanks for taking an interest in this. I appreciate the help.
     

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    #5 Lerronious, Oct 25, 2019
    Last edited: Oct 25, 2019
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    It seems to want analog. Use the 0-10v output but add a 2:1 resistor voltage divider to halve it to 0-5v
     
  7. Lerronious

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    That is what I'll do. Thank you for looking into it.
     
  8. Alex Chambers

    Alex Chambers Openbuilds team
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    Hi @Lerronious, the ratio Peter mentioned was the voltage ratio - you need two equal resistors wired in series. 10 volt output at one end, 0 volts (ground) at the other. The midpoint goes to the program input of your device. I would suggest two 5K ohm resistors would suit.
    Alex.
     

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