On Mon, 26 Dec 2005 01:17:50 -0500, "Henry"
wrote:

Thanks for the link and I have already been to that site. Great site and I
am using it as one of my references.

Problem is that I dont have any 74 series with schmitt triggers. I looked
thourgh my box of old TTL chips. I have nand gates, counters, flipflops, 555
timers, (plus transistors, resistors, capacitors, etc) but nothing with a
schmitt trigger built in. Being out in a rural area and financially drained
(from caregiving for my mother in her last years) I can not justify $25
minimum ordering with S&H for a $0.49 chip. Radio Shack does not carry
these, and my attempts to build my own from transistors in my
box-o-ole-lectronics seems to have failed. Lacking a scope I cant really
tell if what I assemble is working. So I am continuing by trial and error.
All I know is that with what I have built so far I am getting multiple
triggers from the old camera shutter that I have. That is my noisy switch
that I am using.

---
Henry, please bottom post, since it makes it much easier to follow
the chronological flow of the thread. Thanks.

As for your problem, the only really sensible solution is the one
Dan Hollands offered, using a SPDT momentary switch and
cross-coupled gates to form an RS latch. That way _totally_
eliminates all bounce and the period of the output signal is
_precisely_ equal to the time it takes for the swich's common
terminal to get from one contact to the other.

If you've got a quad NAND (7400, LS00, HC00, etc.) and a SPST switch
you can make a latch, like this:


Vcc Vcc
| |
[1K] [1K]
| |
O--| --O---A
|NC | NO NAND Y--+--- OUT
| O +--B |
| | | |
| GND | A--+
| +--Y NAND
| B--+
| |
+------------------+

Now, when you press the switch, the instant the common hits the
normally open contact, OUT will go high and stay high for as long as
you keep the switch pressed. When you release the switch, OUT will
go low the instant the arm hits the NC contact and it will stay that
way until you again press the switch.

Re. your other post, about measuring the actual shutter timing,
what's your idea and what kind of test equipment have you got?

--
John Fields
Professional Circuit Designer