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Thread: Ultimate control over interior lighting

  1. #11
    Newbie impulsenine's Avatar
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    I just know that by the end of this, my EE friends are going to ignore all my calls. In case anybody's curious, I haven't started actually doing much with a carputer -- but am keen on knowing what I'm doing before I do. Leelu (the car) has to have some other things repaired before she has this fancy stuff done to her.

  2. #12
    Banned xdjxklusivex's Avatar
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    http://www.musiciansfriend.com/srs7/...base_id/54796/ :-D i should just mount 4 of those in my car haha... there very bright ive got 6 of them for stage lighting at concerts :-P

  3. #13
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    Do you really think LED is bright enough to light up the whole car?

    The controller,

    Most logical way is to of course connect each LEDs to the main controller unit. As you said lots of long wires are needed.


    Ill do it something like this >>>

    Divide the RGB LEDs into 4s. The 4 RGB LEDS have a controller on board. This board consist of a PIC that drives each color of the LED directly using a PWM. The PIC outputs 4x3 software driven PWM to vary the brightnes of the LEDs. The controller uses 2 wires to comunicates to the main controller, the PC perhaps, using I2C bus.

    The controller have its own address, so you can send a command to that particular set of 4 RGB LEDS only. On top of that you have to define which of the 4 LEDs you want to change colour, then you define how much intensity you want on these RGB.

    So you send something like this >>>

    Controller ID > LED ID > RED VALUE > GREEN VALUE > BLUE VALUE

    For 20 RGB LEDs you need 5 controller of course.

    As you can see you only need 4 wires going into the PC. The power and the serial control lines can all share.

    Can be done.

  4. #14
    Newbie impulsenine's Avatar
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    Chris31 - please define:

    PWM, PIC, I2C bus.

    If I understand this, would you need 50 controllers for 200 LEDs? I'm going to sic a few of the guys I know who got PhD's in Optics and EE ...

  5. #15
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    Quote Originally Posted by impulsenine
    Chris31 - please define:

    PWM, PIC, I2C bus.

    If I understand this, would you need 50 controllers for 200 LEDs? I'm going to sic a few of the guys I know who got PhD's in Optics and EE ...

    Ok Ill explain it very briefly

    PWM = pulse width modulation. Use this techinique to vary the intensity of the LEDs. The output drives the LED directly at a very high frequency, so high that you cant see any flashing. The mark/space determine the intensity of the light. For example, the longer the "on" time of the LED means bright. Less on time, more off time means dim LED. Equal on and off time means medium brightness.

    PIC = A family of microcontroller made by microchips. www.microchips.com. You program this little chips to do what you want really. Can be done in ASM, BASIC or C. They are cheaps all in one solutions.

    I2C = A type of serial communications, requiring a clock signal and data.

    Use google if you want further info.

    If you really want that much LEDs then you will need to control those LEDs serially as I would have done it. Running 3x200 wires plus common ground is messy. The PWM to drive the LED is much much cheaper rather than going for 200 DACs.

    No need to follow the I2C bus. All you really want is each controllers with a bank of 4 RGB leds to react when its address is being called. You can increase the number of RGB LEDs per controller to let say 16, this will reduce the controller needed.

    [PC]=========[0--0--0--0]==[0--0--0--0]==[0--0--0--0]...and so on

    [PC] - The PC you are using to control the LEDs, notice only 2 wires are needed

    [0--0--0--0] - 4 RGB LEDs with controller, each controller have its own unique address

    0 - RGB LEDs

    == - 2 wire serial bus

    Power supply not shown

    Hope that make sense

  6. #16
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    try using a MAX7313 16-Port I/O Expander with LED Intensity Control, Interrupt, and Hot-Insertion Protection

    http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4101

  7. #17
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    Quote Originally Posted by vinthewrench
    try using a MAX7313 16-Port I/O Expander with LED Intensity Control, Interrupt, and Hot-Insertion Protection

    http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4101
    Wow, nice stuff


    Just supply the I2C control, there you go, all done, didnt know they already exist

  8. #18
    Constant Bitrate
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    Or use the phidget led controller, I think it has those maxim chips, it offers 64 leds individually controlled and brightness on individual leds. Plus they already have libraries of code available to make it easy to program. check out www.phidgetsusa.com
    They have tons of other controllers too.

  9. #19
    Newbie evolvd's Avatar
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    Hi, of course a microcontroller of some kinda will be needed. I see the easiest way to get the microcontroller to control a whole heap of LEDs without a ton of wiring is to use the IC bus. Basically its 2 wire communication with multiple devices along the bus. Each device is given an address which the microcontroller can talk directly to the required device.

    In my limited but helpful experience, theres no going past the PICAXE for a simple microcontroller. It can be interfaced directly to computer with serial cable (no interface circuitry needed) and most importantly supports IC. Extremely easy to program using a form of BASIC and built in functions make it easy to interface to anything.

    Although the maxim IC previously mentioned looks to have exactly the same function I stumbled across the PCA9532 (16-bit IC LED dimmer) and remembered this post: http://www.semiconductors.philips.com/pip/PCA9535.html

    They both control up to 16 LEDS individually incl brightness. I was thinking that LEDs may not be bright to light up large areas. However an array of LEDs like 5x blue 5x red and 5x green, should achieve a more than sufficent amount of light. And only 1 IC controls all 16 lights with 2 input wires and up to 8 ICs can be on the one bus (same 2 wires)! Seems like an easy solution.

    The only downer is the Maxim chip controls brightness to 16 increments globally and 16 increments individually, while the Phillips gives 256 increments for each port. Phillips is closer to true colour! But then again you can get free samples from Maxim real easy!

    You can find info on the PICAXE at http://www.picaxe.co.uk/ Look at the datasheets more specifically look at the ones on IC and you will see it should be quite simple to interface the LED controller.

    PICAXEs are quite cheap although im not sure on the price of the other IC (PCA9532).

    At first I thought the idea sounded interesting.. and had thought of doing it myself in a different application, but thought the solution would be too complex. This looks incredibly simple with this solution. Did I mention CHEAP CHEAP (at least the control hardware) !!

    Hope you like it!

  10. #20
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    So I've been looking at these: http://www.superbrightleds.com/light_bars.htm (scroll to bottom)... and @ $25/12" it might be the way to go... maybe 6 total... three per side. Then use the MAX7313 to control the three colors separately--one for each 12" section. (In the docs for the chip it says you can pool pins for more current 50mA/output) So that's 6 controllers... then use a uber-controller to control the output of the 6 sections... you could make the whole car blue, green, white, red, aqua, pink, etc. I think it'd work out.

    -ds

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