Pwm needed

Discussion in 'The Projects Forum' started by j taylor, Feb 13, 2013.

  1. j taylor

    Thread Starter New Member

    Nov 4, 2012
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    Hi i have been looking all over the net to find a pwm circuit to run a led driver using a 555 chip the led driver requires a duty cycle 0v to 1.25v can anyone help me out here with a schmatic i am a nooby to electronics
     
  2. mcgyvr

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    Oct 15, 2009
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    Which LED driver IC?
     
  3. j taylor

    Thread Starter New Member

    Nov 4, 2012
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    Hi MCGYVR
    And thanks for taking the time to respond to my problem the led driver i am trying to use is the ldu2430s1000-wd made by xp power thanks for any help you can give me .
     
  4. thatoneguy

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    Feb 19, 2009
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    Do you have a link to the product page for where you got that unit? I couldn't find a datasheet in a cursory peek at my normal source.

    I'm guessing it is a buck-puck type switching constant current source? If the brightness is determined by the 0-1.25V on the ADJ pin, that could be supplied by either a 555 or a simple potentiometer + resistor if it supports analog input.

    The problem is 555 don't go down to 1.5V. You'd need to divide the voltage down, as well as have several extra components.

    More information will be greatly helpful. Where you got driver, datasheet for same, project it will be going into, size and power limitations.
     
  5. mcgyvr

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  6. j taylor

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    Nov 4, 2012
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    Hi Thatoneguy
    I got the led drivers from farnel lhttp://www.xppower.com/pdfs/SF_LDU08-48.pdf Think this link should work. The project is just to run high power led s useing these drivers but i want to build a pwm to control the brightness and learn about manipulating the 555 as i have no idea how to get 0 to 1.25 out of the 555 to inject to the control pin of the driver when useing a 12v supply any help will be much appreciated .
     
  7. thatoneguy

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    First example on page 4 shows how to implement dimming with only a potentiometer. No 555/PWM source needed.
     
  8. j taylor

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    Nov 4, 2012
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    hi thatoneguy Thats not going to teach me much i want to build the pwm and learn something .
     
  9. spinnaker

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    Oct 29, 2009
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    Did you purchase the controller already? If not take a look at the pt4115 chip. Very easy to use and it has a DIM pin where you can apply PWM.


    Also you can look at a Buck Puck Plus from Luxdrive. Much more expensive but everything is there for you, including +5 vdc regulated that you can use to power your pwm circuit.

    BTW instead of a 555 timer, you could consider using a mcu likes a pic. Your imagination would be the limit on options then.
     
  10. thatoneguy

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    I apologize for trying to be helpful based on your self-professed knowledge of electronics in the OP:
     
  11. j taylor

    Thread Starter New Member

    Nov 4, 2012
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    Hi thatoneguy I didnt mean to sound ungreatfull for what you have suggested i just want to build a pwm that will adjust the drivers i have useing the 555 ic .
     
  12. j taylor

    Thread Starter New Member

    Nov 4, 2012
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    anyone else got any ideas how to get 0 to 1.25v from a pwm
     
  13. j taylor

    Thread Starter New Member

    Nov 4, 2012
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    will someone please help me with this i know this is a very simple thing for you experts and may not seem worth the time to explain to a nooby but its very important to me i have spent the last few days trying to find the answer on the net without any luck and its now driving me mad .
     
    Last edited: Feb 17, 2013
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