??? 06/09/06 03:29 Read: times |
#118066 - They're a crutch ... Responding to: ???'s previous message |
They're a weak crutch for people who can't design logic just as optoisolators are a weak crutch for people afraid to use transistors.
There are conditions where it seems simple, so we're all tempted to use 'em, but DON'T GIVE IN TO TEMPTATION. Anyone who's used 'em quite a bit and had to troubleshoot his work knows that they don't behave well when probed with a 10-Mohm probe, and their trailing edge moves around like crazy. Not only their trigger, but also their reset and timing circuits are sensitive to noise, and I mean noise levels as low as 1% of the supply. DON'T RELY ON 'EM. If you need a one-shot, you can run a counter that gates itself off at a certain count, using the reset line as a trigger. That's at least as good as any one-shot and not nearly so fussy. RE |