Amateur (hack) needs a little guidance...

C

C Logan

Guest
I am simply a hack at electronics but I need a little help...

I have two cats. One is fat because it eats the other one's food. I have
create a special sensor using simple reed sensor switches, a 9 volt and a
piezo buzzer. There is a magnet attached to the cats collar. It works
quite well, when the cat approaches, the magnet triggers one of the reed
switches to close setting off the buzzer.

The problem is that the buzzer only buzzes for a micro - second as the
magnet passes over the reed switch. I want a simple circuit or relay that
stays on for say 5 seconds. When the reed switch closes, it sends 9 volts
to the piezo...isn't there a simple relay or simple basic circuit that can
hold a relay or switch closed for 5 seconds and then open again?
 
C Logan wrote:

I am simply a hack at electronics but I need a little help...

I have two cats. One is fat because it eats the other one's food. I have
create a special sensor using simple reed sensor switches, a 9 volt and a
piezo buzzer. There is a magnet attached to the cats collar. It works
quite well, when the cat approaches, the magnet triggers one of the reed
switches to close setting off the buzzer.

The problem is that the buzzer only buzzes for a micro - second as the
magnet passes over the reed switch. I want a simple circuit or relay that
stays on for say 5 seconds. When the reed switch closes, it sends 9 volts
to the piezo...isn't there a simple relay or simple basic circuit that can
hold a relay or switch closed for 5 seconds and then open again?
Click to expand...
Try a Schmitt-trigger circuit. Google for it.
 
On 27 Jul 2004 16:08:33 -0700, christopher_foy@hotmail.com (C Logan)
wrote:

I am simply a hack at electronics but I need a little help...

I have two cats. One is fat because it eats the other one's food. I have
create a special sensor using simple reed sensor switches, a 9 volt and a
piezo buzzer. There is a magnet attached to the cats collar. It works
quite well, when the cat approaches, the magnet triggers one of the reed
switches to close setting off the buzzer.

The problem is that the buzzer only buzzes for a micro - second as the
magnet passes over the reed switch. I want a simple circuit or relay that
stays on for say 5 seconds. When the reed switch closes, it sends 9 volts
to the piezo...isn't there a simple relay or simple basic circuit that can
hold a relay or switch closed for 5 seconds and then open again?
Click to expand...
Just hang an electrolytic capacitor across the piezo. The sound will
fade out over a period of time; the bigger the cap, the more time.
Piezo oscillators don't use much current.

That's the simplest way to do it.

John
 
On 27 Jul 2004 16:08:33 -0700, christopher_foy@hotmail.com (C Logan)
wrote:

I am simply a hack at electronics but I need a little help...

I have two cats. One is fat because it eats the other one's food. I have
create a special sensor using simple reed sensor switches, a 9 volt and a
piezo buzzer. There is a magnet attached to the cats collar. It works
quite well, when the cat approaches, the magnet triggers one of the reed
switches to close setting off the buzzer.

The problem is that the buzzer only buzzes for a micro - second as the
magnet passes over the reed switch. I want a simple circuit or relay that
stays on for say 5 seconds. When the reed switch closes, it sends 9 volts
to the piezo...isn't there a simple relay or simple basic circuit that can
hold a relay or switch closed for 5 seconds and then open again?
Click to expand...
The name of the type of circuit you are looking for is a "monostable",
more commonly known as a "one shot". A pulse of any duration
sends the output high, and then it stays high for a time determined
by a resistor-capacitor time constant. You can buy ICs that are
dedicated monostables, but I usually prefer to wire up something
simpler from a CMOS gate. Don Lancaster's "CMOS Cookbook"
has a number of circuits, but you can probably find plenty on the
Web via Google.






Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
 
John Larkin <jjlarkin@highsniplandthistechpleasenology.com> wrote:
On 27 Jul 2004 16:08:33 -0700, christopher_foy@hotmail.com (C Logan)
wrote:

I am simply a hack at electronics but I need a little help...

I have two cats. One is fat because it eats the other one's food. I have
snip
Just hang an electrolytic capacitor across the piezo. The sound will
fade out over a period of time; the bigger the cap, the more time.
Piezo oscillators don't use much current.

That's the simplest way to do it.
Click to expand...
And leads to the reed switch welding after a few dozen applications.
 
Dear Bob or others who might help:

First of all, the information provided by Bob was excellent, and I was
able to find an excellent circuit, which I promptly built, and it
works excellent. The circuit I built on the 555 is here.
http://www.kpsec.freeuk.com/breadb.htm

Anyhow, I replaced the switch with magnetic reed switches, and placed
a piezo buzzer in the LED slot. Works excellent except for one thing.
The output voltage is too low...power is supplied by a 9 volt
battery, but it is too quiet because the circuit apparently reduces
output voltage significantly. Any suggestions out there?

-CL



NoSpam@daqarta.com (Bob Masta) wrote in message news:<4107970f.810427@news.itd.umich.edu>...
On 27 Jul 2004 16:08:33 -0700, christopher_foy@hotmail.com (C Logan)
wrote:

I am simply a hack at electronics but I need a little help...

I have two cats. One is fat because it eats the other one's food. I have
create a special sensor using simple reed sensor switches, a 9 volt and a
piezo buzzer. There is a magnet attached to the cats collar. It works
quite well, when the cat approaches, the magnet triggers one of the reed
switches to close setting off the buzzer.

The problem is that the buzzer only buzzes for a micro - second as the
magnet passes over the reed switch. I want a simple circuit or relay that
stays on for say 5 seconds. When the reed switch closes, it sends 9 volts
to the piezo...isn't there a simple relay or simple basic circuit that can
hold a relay or switch closed for 5 seconds and then open again?

The name of the type of circuit you are looking for is a "monostable",
more commonly known as a "one shot". A pulse of any duration
sends the output high, and then it stays high for a time determined
by a resistor-capacitor time constant. You can buy ICs that are
dedicated monostables, but I usually prefer to wire up something
simpler from a CMOS gate. Don Lancaster's "CMOS Cookbook"
has a number of circuits, but you can probably find plenty on the
Web via Google.






Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Click to expand...
 
"C Logan" <christopher_foy@hotmail.com> wrote in message
news:f258c75f.0408191043.189751e1@posting.google.com...
Dear Bob or others who might help:
NoSpam@daqarta.com (Bob Masta) wrote in message
news:<4107970f.810427@news.itd.umich.edu>...
On 27 Jul 2004 16:08:33 -0700, christopher_foy@hotmail.com (C
Logan)
wrote:

I am simply a hack at electronics but I need a little help...

I have two cats. One is fat because it eats the other one's
food. I have
create a special sensor using simple reed sensor switches, a 9
volt and a
piezo buzzer. There is a magnet attached to the cats collar. It
works
quite well, when the cat approaches, the magnet triggers one of
the reed
switches to close setting off the buzzer.

The problem is that the buzzer only buzzes for a micro - second
as the
magnet passes over the reed switch. I want a simple circuit or
relay that
stays on for say 5 seconds. When the reed switch closes, it
sends 9 volts
to the piezo...isn't there a simple relay or simple basic circuit
that can
hold a relay or switch closed for 5 seconds and then open again?

The name of the type of circuit you are looking for is a
"monostable",
more commonly known as a "one shot". A pulse of any duration
sends the output high, and then it stays high for a time
determined
by a resistor-capacitor time constant. You can buy ICs that are
dedicated monostables, but I usually prefer to wire up something
simpler from a CMOS gate. Don Lancaster's "CMOS Cookbook"
has a number of circuits, but you can probably find plenty on the
Web via Google.


First of all, the information provided by Bob was excellent, and I
was
able to find an excellent circuit, which I promptly built, and it
works excellent. The circuit I built on the 555 is here.
http://www.kpsec.freeuk.com/breadb.htm

Anyhow, I replaced the switch with magnetic reed switches, and
placed
a piezo buzzer in the LED slot. Works excellent except for one
thing.
The output voltage is too low...power is supplied by a 9 volt
battery, but it is too quiet because the circuit apparently reduces
output voltage significantly. Any suggestions out there?
Click to expand...
First, on s.e.b, please reply at the bottom of a post, never at the
top. This is simply a convention.

Secondly, you can use a pass transistor to get around the
current/voltage limiting using an external transistor, like this:

9V
|
.--+---.
|Buzzer|
'--+---'
1k |
Output ___ |/
From -|___|- -| NPN like 2N2222 from Radio Shack or Maplin
555 |>
|
GND

created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

When the output of the 555 goes high, it'll turn on the NPN
transistor, allowing current to flow.

--
Regards,
Bob Monsen
 
"C Logan" <christopher_foy@hotmail.com> wrote in message
news:f258c75f.0408191043.189751e1@posting.google.com...

http://www.kpsec.freeuk.com/breadb.htm

Anyhow, I replaced the switch with magnetic reed switches, and placed
a piezo buzzer in the LED slot. Works excellent except for one thing.
The output voltage is too low...power is supplied by a 9 volt
battery, but it is too quiet because the circuit apparently reduces
output voltage significantly. Any suggestions out there?
Click to expand...
Is your 555 a CMOS version (LMC555, TLC555) or a bipolar version (NE555)?
Try the latter; it can conduct quite a bit more current.
 
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