Modern Blinkenlights

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Fri Jun 18 20:13:05 2004

> The only Linux cpu load/led display projects I could find work as Tony
> described .
> ledstatus-0.1.tar, meter-0.2.tar, and qmeter-1.0.tar all use one led & a
> resistor
> on each parallel port line D0-D7 (two leds not used).
>
> Which is disappointing because I wanted to use a big old analog radio meter ;)

If you really want an analogue display (that old meter), can't you
connect some resistors (maybe with series diodes) to the parallel port?

If the display is a bargraph (more LEDs on for more load), then try
something like this :


D0 --->|---/\/\/\-----+
                      |
D1 --->|---/\/\/\-----+
                      |
D2 --->|---/\/\/\-----+
                      |
D3 --->|---/\/\/\-----+
                      |
D4 --->|---/\/\/\-----+
                      |
D5 --->|---/\/\/\-----+
                      |
D6 --->|---/\/\/\-----+
                      |
D7 --->|---/\/\/\-----+
                      |
                    (meter)
                      |
                     ---
                     ///

Pick the resistors (all the same value) so that the meter gets to FSD
when all the otuput bits are set. Diodes can be 1N4148 or similar. This
is not going to be a precision circuit, but it should be good enough for
this.

If the display is just one LED on (D7 meaning more load than D0), then
try making the resistor on D0 8 times that on D7, the one on D1 7 times
that on F7 and so on. Again, not a precision circuit, but it'll do.

-tony
Received on Fri Jun 18 2004 - 20:13:05 BST