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Thread: Using Arduino to Auto-dim LED EBY701?

  1. #1
    Constant Bitrate
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    Using Arduino to Auto-dim LED EBY701?

    I have an arduino board and ... well, I want to put it to use.

    Does anyone know if it is possible to power the LED Backlight system in the EBY701 with your own power source? So.. instead of the EBY701 circuit board controlling/powering the backlight, I'd like to use my Arduino board to power/control the LED backlight and install an ambient light sensor in my vehicle somewhere so that at night the backlight automatically goes LOW and in the day, it automatically goes HIGH.. maybe have a feathering code on the arduino so it slowly fades between brightnesses when going through tunnels, etc...

    Being that the Arduino board is interfaceable to the computer through USB, even bluetooth and WIFI, a small front end touch-friendly GUI could be coded to be able to add a menu to centrafuse/roadrunner to allow manual control of the screen brightness settings through software.


    Anyone interested and want to help a buddy out with this idea?

    Thanks!

    -steve

    stevey500(at)gmail.com

  2. #2
    Vendor - Qube colin's Avatar
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    You got any experience with PWM? Any equipment to measure the power going through the LEDs currently? Shouldn't be too hard, really...

  3. #3
    Constant Bitrate
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    I do not have experience with PWM ... hmm, I have never programmed an arduino ever, willing to learn and experiment, having someone help me out that already has done much of this stuff would be a hella lot of help in getting in done quickly. Thanks man.

  4. #4
    Vendor - Qube colin's Avatar
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    First things you need to know:

    1) PWM frequency of whatever is currently driving the LEDs
    2) voltage for the LEDs
    3) current through the LEDs
    4) which of these things change when the display is dimmed

    Take some measurements, and then you can replicate the results via Arduino (or a better board perhaps)...

  5. #5
    Raw Wave
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    Stevey may not need to know the LED parameters other than a suitable switching frequency - though 400Hz is a typical on many dimmers (except where flicker occurs...).

    It is simply a matter of varying the duty cycle of the LEDs for dimming.

    It is current (not voltage) that is varied - ie, duty cycled.

    If controlling whatever currently (pun) controls the LEDs, you merely modulate that (eg - transistors or FETs).

    Could also insert a MOSFET into the LEDs' + or -ve supply.

    In either case, LED voltages & currents need not be known (other than total LED current, but that is unlikely to be higher than what any MOSFET can handle).

  6. #6
    Vendor - Qube colin's Avatar
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    Yeah I was thinking LED current for a MOSFET. Cut the control line, modulate it yourself.

    I don't know how to use an Arduino, but I think there's an analogWrite function which starts a PWM? Not 100% how it works but I think you just give it a level -- analogWrite(255) would be full on? Not sure how you set up frequency though.

  7. #7
    Raw Wave
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    There are sample programs - LED dimming is a popular one.
    I think they are in C++ or similar.
    Just search...

    But PWM should be a digital out unless you have a voltage to PWM circuit.
    These days many have inbuilt PWM functions.

  8. #8
    Maximum Bitrate Crinos's Avatar
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    First result on Google with search phrase "Arduino led dimming"

    http://www.arduino.cc/en/Tutorial/DimmingLEDs

  9. #9
    Vendor - Qube colin's Avatar
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    Too complicated, you don't want crossfading.

    I'm pretty sure you just do analogWrite(0-255) to set a duty cycle on a PWM output...

  10. #10
    Raw Wave
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    So Stevey thinks it's too complicated?

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