The circuit presented here (see figure) provides users with an indication of a high or low logic state. When the input is a logic 1 (high), the common-cathode display indicates "H." When the input is a logic 0 (low), the display indicates "L."
The circuit uses one gate out of four in IC N—a 7400 quad, two-input NAND gate— to invert the input and apply the output to the d, e, and f segments of the display via an emitter follower (T1). The diodes and the resistors suitably buffer the direct and indirect inputs (via the emitter follower) to segments e and f. The device operates from a regulated +5-V power supply.
I usually use one resistor in series with one LED to probe a logic level, only two passive components but it works. You can even use as high as 10k Ohm resistor and still be able to see the LED light If you don't want to interfere the measured circuit much. Anyway, your circuits look much more sophisticated than mine :) ---------------www.softhardzone.com : high quality freeware, electronic design and software programmin trick and tips.
Ant -October 26, 2007
Uhmm, did this by any chance miss the April 1 issue? Now if a prom had been used to select arbitrary language that would be cool.
Anonymous -May 30, 2007 (Article Rating: )
Your Comments:
Enter the text from the image below
Please refresh the page if you have trouble reading this text.
Search Electronic Design
Email Newsletter
Sponsored By:
Electronic Design UPDATE provides readers with late-breaking news, opinions from industry experts, and timely technology stories. It's a unique opportunity to get your product message in front of engineers, engineering managers, and corporate managers while they're reading about critical information online.
Reprints
)
