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Subject: Re:Backlight on recorder dimming?
From: Chris Muth (muthchris_at_mchsi.com)
Date: 2002-12-31


Hey,

I too have noticed that the backlight will dim slightly when the disk spins up.
I have also noticed that backlight will get slightly brighter when I apply pressure to the
face plate. This is almost certainly a physical thing. Perhaps the light spreader is getting
closer to the LED array and therefore the uneven propagation pattern ot the light being emitted by
the diode is focused in such a way to provide more light? [Chris is just thinking into the keyboard]
That is not a big deal and is beside the point.

Even when the disk is not spinning, spinning up, or spinning down, I can press the
volume up/down (other buttons work but I will go with this example) button and the
back light will come on and after 4s (the time I have it set for) it will get slightly brighter,
and then get progressively dimmer and dimmer until the LEDs are off. Off to the best my
feeble optic nerve can determine. I am willing to crack it open and stick the backlight on the
oscope and see what truly is happening.

Being that this is a digital device, I am guessing that there will be many discrete voltage levels going
into the backlight, and not random rail noise that would suggest that the disk is putting noise on the
power rail.

Thank You for the responses.

Best Regards,
        Chris Muth <muthchris_at_muth.cc>

>Andreas Stemmer <Andreas.Stemmer_at_web.de> wrote:
>I had the same impression with my AJBR20: the backlight dims when the
>harddisc spins up because there's not enough power provided. If you want to
>program some dimming effects, you could use very fast on/off switching
>(pulse width modulation) which works quite well with any led like the
>backlight leds.
>
>Andreas Stemmer
>
>> >>I think the dimming is pretty cool, I just can't figure out why if
>appears
>> to get yellow and
>> >>I can't quite figure out what determines whether it dims or just goes
>off.



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