Op Amp, LED flicker

Discussion in 'The Projects Forum' started by cjeung, Dec 8, 2013.

  1. cjeung

    Thread Starter New Member

    Mar 31, 2011
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    I've built this op amp circuit to boost power to a PWM LED light control. I'm controlling circuit using Arduino controller. When I set the values to 0 (off), after a second or two, I start to get some light flickering. I'm not trained in electronics, so I'm guessing I may need a pull down resistor. Could use advise on if I'm correct, and where I might need to place them.

    the Arduino pins (3,11) are supplying source PW to the op amp. Can I place pull down resistors at the (+) inputs? anything else? Also, ont other thing that may be important, the output pulse are connected to control leads of an LED power supply. In case you think it's overdriving the PWM (just thinking out loud).

    Many Thanks to the experts at ABC
     
    Last edited: Dec 8, 2013
  2. Maxfooo

    New Member

    Aug 24, 2013
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    Hello cjeung,

    I am no pro either, but I think I have two or so sense to put in. Generally you want to utilize the negative input in an op-amp simply because of the operation of the amplifiers are generally designed to have the signal be put into the inverting side. Second it would be worth while to actually use a comparator for your purpose of PWM because you are not looking for any sort of variable gain. Third, your right about putting a pull down resistor in the circuit. In your case you could very well put a 100k resistor at the non-inverting input (the output of you I/O), but I recommend, again, that you use the inverting input and either put the signal through through another inverting comparator, or an inverter. If you choose to go that route, then you do not need the feedback because you are not looking for any noise immunity, as you configuration would allow for. What the feedback is doing, to me it seems, is that is is protecting the output signal from any wavering input signal, but with your pull-down installed, and the I/O pin coming from the arduino as a PWM, there will be very insignificant noise.
    [​IMG]

    Hope this helps!
     
  3. Maxfooo

    New Member

    Aug 24, 2013
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  4. Maxfooo

    New Member

    Aug 24, 2013
    17
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    ooops, noob here lol, forgot to place ground on non-inverting side of second comparator.
     
  5. Maxfooo

    New Member

    Aug 24, 2013
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  6. Maxfooo

    New Member

    Aug 24, 2013
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  7. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Step 1.
    What is it you want to accomplish?
     
  8. cjeung

    Thread Starter New Member

    Mar 31, 2011
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    The Arduino will put out a 5v pulse, but the light controller needs a 10v pulse. from what I've guessed, I only needed to amplify the 5V pulse.

    I'm also driving two LED circuits with two pin outs form the single controller. I figured it was easier to make the op amp circuit rather than driving two mosfets.

    I can vary the intensity of the lights as planned, but when they're supposed to be off, the flicker starts.
     
    Last edited: Dec 8, 2013
  9. jayanath

    New Member

    Dec 11, 2010
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    help me to make 12 led chaser with comet tail effect. where to go?
     
  10. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    10V at ? amperes is required by the light controller?

    Do you have that schematic or a model number?
     
  11. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,374
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    http://blog.irwellsprings.com/pwm-led-comet-effect-using-a-pic-micro/
    "This is a response to a comment on Getting Started with PIC Microcontrollers – the PWM Peripheral from Jayanath,

    which requested some example code for a “12 LED chaser with comet tail effect”.



    Dude! You effing famous!
     
  12. cjeung

    Thread Starter New Member

    Mar 31, 2011
    8
    0
    The power supply that I'm using for the LED was purchased from Jameco. HLG-150H-36b.

    I'm going to wire two 50w LED panels to each. ordered them from Ebay, here is a link.
    http://www.ebay.com/itm/251316532661?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

    and I'm driving them with the Arduino hooked up with an LCD control shield

    truth to tell, I'm not great at focusing on proper current problems, I just made sure I had enough current for two panels in parallel. And I've only run the test circuit with one (perhaps that's my problem? please confirm).
     
  13. cjeung

    Thread Starter New Member

    Mar 31, 2011
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    I hope this didn't kill my thread with an unrelated request and a supporting answer. I'm still working on a solution to my project and will re-engage on the following post
     
  14. cjeung

    Thread Starter New Member

    Mar 31, 2011
    8
    0
    Okay, so here's an update on my project light controller. My plan is to use the Meanwell: HLG-150h-36b power supply to control my LED panels. The PWM leads require a 10v control voltage. My Arduino only puts out a 5v pulse. I found out that the PWM control leads have 6.0v running through them. (I didn't see any information about this prior to my testing).

    I tried:
    using an op-amp circuit (non-inverted), but the LED's flickered when the PWM was set to 0. I recently read that an Op Amp is not stable at 0v and that it may need some -v setting.

    I tried using a MOSFET the the Lights went on regardless of any PWM setting on the Arduino. Same thing applied to my trying a Bipolar NPN transistor. Do I need to factor in any current that the PWM leads are using? Is that why these components didn't seem to cut out the power? I've used the common basic schematics for connecting these components.

    Obviously I have more research to do, but a helpful direction may help. Sorry if I haven't given sufficient information. Not even sure what to include
     
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