[sci.electronics] Monitoring Digital Levels with an LED

dylan@cs.washington.edu (Dylan McNamee) (10/31/89)

I would like to add a coulple of status lights to my CD player.  I have
located pins where the Track Lost and Drop Out Detector signals are.  
I would like to hook up an LED to these signals, but I don't want to 
add any noise to the circuitry.  (I was thinking of using a battery
to power the LED.)

Any ideas of how to do this?  I've always wanted to know how many times
my CD player was actually interpolating data...

Send me replies, if you wish, and I'll summarize the ideas, if there is
interest.

dylan
dylan@cs.washington.edu

dag@hp-lsd.COS.HP.COM (David Geiser) (11/02/89)

Quick and Dirty:

Let the outputs drive the base of a small transistor which will 
turn on the LED.  You might want to add a capacitor time delay
in the base circuit to slow down the rate at which the transitor
is turned off after it is turned on.  Otherwise, the pulses may
be too narrow to see.   Hmmm, looks like I've just described a
one-shot (retriggerable would be nice).