Meanwell LDD PWM questions.

Discussion in 'The Projects Forum' started by AJS14, Jan 11, 2016.

  1. AJS14

    Thread Starter New Member

    Feb 4, 2014
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    0
    Hello,

    http://www.meanwell.com/mw_search/ldd-h/LDD-H-SPEC.PDF
    The Meanwell LDD series datasheet says this about remote on/off and PWM dimming:

    DIM: ~-Vin>2.5~6VDC or open circuit
    PWM Frequency: 100~1KHz

    Does this mean that there should be 2.5-6v coming back out of the device to the power supply? When it says open circuit it's not talking about the -Vin wire being open but the PWM wire right?

    PWM frequency means that any PWM signal in this band of 100-1Khz will work to drive the PWM? The duty cycle % being carried somewhere on that frequency band.



    Thanks in advance.
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    969
    LDD's typically require 5V PWM for dimming.. 0% duty cycle is off 100% duty cycle is full on.
     
  3. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,287
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    No, it means the pwm signal should be above 2.5 volts.
    Yes the pwm wire

    Yes



    Thanks in advance.
     
  4. AJS14

    Thread Starter New Member

    Feb 4, 2014
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    0
    http://forum.allaboutcircuits.com/threads/leds-555s-flashers-and-light-chasers.19075/#post-117641

    So this input frequency seems a bit on the low end.
    Im looking at using Bill's 5.3 figure on his 555 page and using .47uF as the capacitor and a 1K5 for R2 and a 10K pot in R1.
    There's a comment I found that current on r1 needs to be under 10mA so If I were planning on using a TLC555 running the network on 5v R2 would have ~3.2mA going across it.

    Using these resistor values with that size timing cap gets me just within the boundaries of the PWM spec on the LDD.

    Also fig 5.3 shows a pull up resistor in a block with a red LED and transistor. If I don't intend to drive that LED and I just want to send the PWM signal out to the LDD can I just use the pull up resistor and leave the rest out?
     
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
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    I would just use the one on the left without the LEDs.
    [​IMG]
    Then you can just drive it with pin 3. The 555 has an active pull up.
     
  6. AJS14

    Thread Starter New Member

    Feb 4, 2014
    10
    0
    Are there specific diodes I should use for CR1 &CR2?

    The equation here goes way up to 14kHz at low values of R1. Since the values sum I can add whatever value I need in series with R1 to cap the frequency for the spec on the driver right?

    thanks again.
     
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