Modern Blinkenlights

From: meltie <lists_at_microvax.org>
Date: Fri Jun 18 15:41:50 2004

On Friday 18 June 2004 20:13, Tony Duell wrote:
> > I've seen a pretty easy-to-build circuit to put one of those on a
> > Linux box. I remember something about a simple resistor ladder
> > network D-A and an LED bargraph chip from Radio Shack. The software
> > just puts the load on a spare parallel port, so it's pretty
> > low-impact.
>
> Are you serious? If so, I have to wonder if anyone can actually _design_
> any more, or if they just throw standard modules together and hope it
> works.
>
> Let me see if I understand this. You have a digital value (system
> usage), on a digitial machine (the linux box). You convert it to
> analogue. You then re-convert it to digital with a very low-res ADC (the
> LM3914 (I guess) bargraph chip. Why not just output a suitable value on
> the parallel port (which has 12 output lines IIRC) to directly drive the
> LEDs (the 3914 drives 10 LEDs at most).
>
> -tony

I don't know the one he's talking about but the most popular one all over
the web (and the one that i've got lying around from my old mail server)
just has 10 LEDs driven directly from the port with a common resistor.

alex/melt
Received on Fri Jun 18 2004 - 15:41:50 BST