Help with single pulse circuit

T

The Jackal

Guest
I'm sort of a beginner when it comes to electronics. What I need is a
circuit that will receive +VCC for a fixed amount of time (say a
minute) but only give out one single pulse until the circuit is reset.
I need this to run one of those house bells that run on batteries,
where you only need to press it once. Connecting it directly to the
circuit wouldn't do, since it would keep on ringing as long as the
+VCC is on, whereas I only want one ring.

Thanks.
 
Wouldn't it be be best way to use the button to directly turn on and off the
voltage source? I don't know if there is a reason for wanting a separate
circuit so post a reply if if missed something.

Andrew Howard


"The Jackal" <jalouan@idm.net.lb> wrote in message
news:d089193b.0309281540.102505bb@posting.google.com...
I'm sort of a beginner when it comes to electronics. What I need is a
circuit that will receive +VCC for a fixed amount of time (say a
minute) but only give out one single pulse until the circuit is reset.
I need this to run one of those house bells that run on batteries,
where you only need to press it once. Connecting it directly to the
circuit wouldn't do, since it would keep on ringing as long as the
+VCC is on, whereas I only want one ring.

Thanks.
Click to expand...
 
"The Jackal" <jalouan@idm.net.lb> wrote in message
news:d089193b.0309281540.102505bb@posting.google.com...
I'm sort of a beginner when it comes to electronics. What I need is a
circuit that will receive +VCC for a fixed amount of time (say a
minute) but only give out one single pulse until the circuit is reset.
I need this to run one of those house bells that run on batteries,
where you only need to press it once. Connecting it directly to the
circuit wouldn't do, since it would keep on ringing as long as the
+VCC is on, whereas I only want one ring.

Thanks.
Click to expand...
Sounds like you need something like a one-shot or similar. Perhaps
something like the 74HC4538 might be what you are looking for.

http://www.fairchildsemi.com/ds/MM/MM74HC4538.pdf
 
"Fritz Schlunder" <me@privacy.net> wrote in message
news:bl8pu3$9g2q4$1@ID-203926.news.uni-berlin.de...
"The Jackal" <jalouan@idm.net.lb> wrote in message
news:d089193b.0309281540.102505bb@posting.google.com...
I'm sort of a beginner when it comes to electronics. What I need is a
circuit that will receive +VCC for a fixed amount of time (say a
minute) but only give out one single pulse until the circuit is reset.
I need this to run one of those house bells that run on batteries,
where you only need to press it once. Connecting it directly to the
circuit wouldn't do, since it would keep on ringing as long as the
+VCC is on, whereas I only want one ring.

Thanks.

Sounds like you need something like a one-shot or similar. Perhaps
something like the 74HC4538 might be what you are looking for.

http://www.fairchildsemi.com/ds/MM/MM74HC4538.pdf
Click to expand...
Depending upon exactly what you want perhaps a non-retriggerable version
might be better like the 74HC221A:

http://www.fairchildsemi.com/ds/MM/MM74HC221A.pdf

They make 4000 series logic version of these devices for use at up to 15
volts or so as well.
 
"Fritz Schlunder" <me@privacy.net> wrote in message news:<bl8q95$99qbv$1@ID-203926.news.uni-berlin.de>...
"Fritz Schlunder" <me@privacy.net> wrote in message
news:bl8pu3$9g2q4$1@ID-203926.news.uni-berlin.de...

"The Jackal" <jalouan@idm.net.lb> wrote in message
news:d089193b.0309281540.102505bb@posting.google.com...
I'm sort of a beginner when it comes to electronics. What I need is a
circuit that will receive +VCC for a fixed amount of time (say a
minute) but only give out one single pulse until the circuit is reset.
I need this to run one of those house bells that run on batteries,
where you only need to press it once. Connecting it directly to the
circuit wouldn't do, since it would keep on ringing as long as the
+VCC is on, whereas I only want one ring.

Thanks.

Sounds like you need something like a one-shot or similar. Perhaps
something like the 74HC4538 might be what you are looking for.

http://www.fairchildsemi.com/ds/MM/MM74HC4538.pdf



Depending upon exactly what you want perhaps a non-retriggerable version
might be better like the 74HC221A:

http://www.fairchildsemi.com/ds/MM/MM74HC221A.pdf

They make 4000 series logic version of these devices for use at up to 15
volts or so as well.
Click to expand...
Are you implying that a 4528/4538 can't be configured as
non-retriggerable? Check the data sheet. It can be wired for + edge, -
edge triggering and either retriggerable or non-retriggerable. Also,
the time constants for 4538 are the simplest there are. See page 9 of
the ON semi PDF.
http://www.onsemi.com/pub/Collateral/MC14538B-D.PDF

I just looked through the Fairchild data sheet. No wonder you're
confused. I always liked the Motorola (now ON semiconductor) data
books when I played with CMOS 20+ years ago. I'm sure glad I didn't
see the Fairchild (type) books first.
gg
 
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