RJR posted:Adrian, going to Digikey, I see many variations of the CD74HC123. Why the differences and which is best? Note Adrian asked a question about resistors & caps.
Hi again... I went with exactly this chip. There's no design reason, it was just in stock the week I needed it. All the people who make 74xx chips (TI, ADI, ON, ...) have different underlying fabrication processes for the CMOS technology so you get different timing numbers depending on which brand you buy. Again on the resistors and caps 5% should be more than enough. Everything is order of magnitude-ish insensitive so if you buy 1K,5K,10K,100K resistors and 0.01uF, 0.1uF, and 1uF caps, you will definitely have a few combinations that work. The only one that's critical is the one for the LED so you don't blow it with too much current.Note the LED doesn't have to be blue.... I just think they look fancy.
