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Electronics Halo Lamps Fader Circuit?

Discussion in 'Modding' started by Cam, 9 Jun 2006.

  1. Cam

    Cam What's a Dremel?

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    I'm hoping someone can offer some help designing a circuit for an automotive application.

    I have 4 CCFL (Fluro) halos, designed for automotive use. Before you ask, I don't know their wattage or current usage - have requested those figures, but let's estimate 10W x 4 halos.

    These halos can be seen as standard on recent model BMWs and are used as daytime running lights. They are also sometimes referred to as Demon Eyes or Angel Eyes.

    I'm looking to install these on a Mazda, but rather than have them connected to the ignition, or to the parking lights, I want to them triggered by remote - ie when you lock or unlock the car. I also want to have a cabin switch so that the driver can select the halos on or off. And finally, I'd like to fade the halos on or off smoothly.

    The logic is this:

    Unlock the car by remote. The halos fade on. If the cabin switch is ON, the halos stay on. If the cabin switch is OFF, the halos fade back off again after a predetermined short delay.

    Whilst the car is unlocked, if the driver changes the cabin switch from OFF to ON, the halos fade on and stay on. And vice versa.

    Lock the car by remote. If the cabin switch was ON (hence so were the halos), then they just fade off. If the cabin switch was OFF, then the halos fade on, then off again.

    If someone can design a circuit, I can get the PCB's made up and build the units, but it's too long ago since I last did any circuit theory to calculate values or analog design. A micro-controller is an option, but bear in mind the application is automotive and must be vibration and environment tolerant.

    Further questions and suggestions can be mailed to me. I have some circuit simulation software for prototyping, but happy to hear of suggestions of better stuff (I've toyed with Circuit Shop and SimEx)

    Cheers - Cam
     
  2. agent420

    agent420 What's a Dremel?

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    Here's a similar circuit for a starting point. While targeted towards the dome light, the principle is the same. The transistor used is rated for 75W, but might need a heatsink if you push it hard.

    Googling for dome light dimmer circuits will return several other examples.

    I imagine you have some type of relay or trigger from your remote unit that will control this?
     
  3. cpemma

    cpemma Ecky thump

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    I think there's a typo error on the schematic. He's showing a 39k base resistor on the switching transistor T1. A 12V supply allows a max of under 0.3mA base current through 39k. So the transistor would need a gain of over 1000 to light a 3W bulb... and a 3055 has very low gain, under 100. A 390 ohm resistor might work, but for anything brighter than a dome light I think you'll need the gain of a darlington like a TIP122.

    For dimming CCFL lamps you really need a PWM system, reducing DC voltage tends to give a short range going out unevenly along the length.
     
  4. agent420

    agent420 What's a Dremel?

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    Oops. The ccfl bit failed to register in the remaining neurons. Quite right, pwm is more appropriate.
     
  5. Cam

    Cam What's a Dremel?

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    I don't really think a dome-dimmer circuit is what I'm after, although the "fader" sub-module is probably applicable for the fade-out part.. Fade in, I'm given to understand, is a different story again.

    Excuse my newb-ness, but what is a PWM system? Does anyone have circuit or idea specific to CCFL's, with the required logic taken in to account?
     
  6. mottl3y

    mottl3y What's a Dremel?

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    PWM refers to pulse width modulation.

    That's all i got.
     
  7. Cam

    Cam What's a Dremel?

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    Any further thoughts anyone?
     

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