FELLOWS@UNB.CA (09/22/90)
A question for George. Can a 22microfarad tantalum cap. be substituted for C47 (33 microfarads called for)? I'm quoting C47 from memory, but it is the one in what I assume is the reset switch de-bounce circuit. Dave Fellows
george@wombat.bungi.COM (George Scolaro) (09/23/90)
[In the message entitled "C47 value" on Sep 22, 12:10, FELLOWS@UNB.CA writes:] > > A question for George. Can a 22microfarad tantalum cap. be substituted > for C47 (33 microfarads called for)? I'm quoting C47 from memory, but > it is the one in what I assume is the reset switch de-bounce circuit. > > Dave Fellows The reset cap value is pretty well a seat of the pants choice - it only needs to be large enough to give a 'long enough reset ' in combination with the pull up resistor and the input of the 74xx14. Long enough is based on reliable power-on reset - which is dependent on the power supply you are using. As long as you pc532 powers up every time without an additional press of the reset button, then the cap is big enough. Since the time constant is k x RC, you can make up for a smaller C with a larger R. The RC for the reset is not for de-bounce but for generating a reset during power supply power up. best regards, -- George Scolaro george@wombat.bungi.com [37 20 51 N / 122 03 07 W]