LEDs Was: Re: Emulation (Was: Emulators of Classic

From: der Mouse <mouse_at_Rodents.Montreal.QC.CA>
Date: Sat Jan 17 16:54:31 2004

>> [writing about my CA pipe-dream]
> Also, i don't think it is feasible as such will not be able to handle
> all the power that would be o/p(heat i mean), which would be in
> Watts!!(too high for ICs)

Too high for ICs? CPU chips regularly dissipate multiple watts. And
as I pointed out, I don't want the LEDs to be as bright as most
discrete LEDs. Consider a 4dpi panel made out of discrete LEDs.
Assume the figures given before (2V drop, 10ma current). Then a square
foot of panel pulls 48*48*10ma*2V = 46.08 watts (without considering
how much becomes light and how much heat). I wouldn't expect a square
foot of this panel to be drawing any more than that, at least at low
clock rates. It might even draw significantly less, since I don't
expect fully-lit area to be as bright as those low-res panels (which
are usually intended to be looked at from large distances, like at
least across the street). Assuming the aggregate draw to be the same,
the LEDs would pull 10ma*(4dpi*4dpi)/(75dpi*75dpi) = about 30?a each.

I have some discrete LEDs with clear housings. I tried two of them in
back-to-back parallel, with a 1M series resistance, across 120VAC mains
voltage (the idea being that I can ignore the LED voltage drop when
figuring the current), for about 120?a. This produced a clearly
visible glow, despite being spread out by the lens. I feel sure 30?a
would be plenty, given an housing optically appropriate to the purpose.

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Received on Sat Jan 17 2004 - 16:54:31 GMT