Help needed designing simple circuit

[whit3rd]

On Mar 24, 2:39 pm, David Nebenzahl <nob...@but.us.chickens> wrote:

Function:  person has a motion-detector light installed in their home.
They want a buzzer/bell/annunciator of some kind to go off *momentarily*
whenever the light is activated.

There are motion detectors in the X10 lineup that wirelessly
communicate with a variety of modules; ring a chime, turn on a light,
whatever floats your boat. OK, I realize this is a learning
hobby-style project....

 

[Baron]

David wrote:

"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:49d0228d$0$29738$822641b3@news.adtechcomputers.com...
On 3/29/2009 6:43 AM Baron spake thus:

David Nebenzahl wrote:
Ok but excuse the ascii art.

live ----diode---relay---resistor---capacitor---neutral

You're excused. That illustrates the circuit perfectly.

Size the resistor to give the time constant with a
particular value
capacitor. The relay contacts are isolated and can be
connected to
your low voltage circuit.

The resistor should have sufficient wattage rating with
respect to the
current and the capacitor should be rated for at least
the maximum
voltage applied. ie 120v X 1.414. The relay can be
almost anything
with a suitable coil voltage. ie 100 - 120.

The circuit works by utilising the charging current into
the capacitor
to energise the relay. As the capacitor voltage
increases the relay
will drop out. The time difference between energising
and dropping out
is how long the annunciator will sound.

So I take it you'd like this circuit:
http://www.geocities.com/bonezphoto/misc/One-shotBell2.gif

And now can you give us the R and C values to give, say, a
1- or 2-second on time? I don't know how to calculate such
things. (Understand how they work, just never learned the
actual math involved.)

I thought you learned that there should be a discharge path
for the capacitor unless you want to wait hours or days
before it will work a second time.

David

Sorry my error I forgot to put one in :-(
You need to bleed about 1/10th of the relay current.
It should go directly across the cap.

--
Best Regards:
Baron.

 

[Andy]

On Mar 28, 1:00 pm, David Nebenzahl <nob...@but.us.chickens> wrote:

On 3/27/2009 3:55 PM Tim spake thus:





In article <49c944ff$0$29984$82264...@news.adtechcomputers.com>,
nob...@but.us.chickens says...

(famous last words, "simple circuit" ...)

OK, so I'm trying to come up with a simple (maybe even elegant) solution
to a simple problem. Have an idea I want to run by y'all.

Function:  person has a motion-detector light installed in their home.
They want a buzzer/bell/annunciator of some kind to go off *momentarily*
whenever the light is activated.

Here's my idea for the circuit:
http://www.geocities.com/bonezphoto/misc/One-shotBell.gif

OK, so a lot of issues here deal with the AC power being detected and
transferred to something useful. I did a simple data logger for my well
pump (URL:http://personal.nbnet.nb.ca/snowowl/DataRecorder.html), that
had to deal 220V being sensed. I used a cheap little cell phone / palm
pilot charger that was universal 110/220 50/60hz and wired it parallel
with the motor leads. This gave me a nice 5 volts when the power was
applied to the pump, so I could log it's on cycles. You still have to
wire it up the the light, so that's a danger here as well. Dealing with
AC mains wiring, there always a need for extra safety.

Thanks for your reply.

Unfortunately, your solution, while interesting, misses one of the
requirements of the whole deal: it needs to operate the
bell/chime/annunciator *momentarily*, not continuously.

--
Made From Pears: Pretty good chance that the product is at least
mostly pears.
Made With Pears: Pretty good chance that pears will be detectable in
the product.
Contains Pears:  One pear seed per multiple tons of product.

(with apologies to Dorothy L. Sayers)

First of all, I think that figuring things out is exactly what these
forums are for. I think your circuit is too complicated. I do this
kind of circuit all the time, but I usually use digital components and/
or comparators, microprocessors, etc. But I like your idea of using
the RC charge cycle. My version of your circuit includes a small DC
relay. Let me try to explain it, since I'm not educated enough to
figure out how to post a drawing. The 120V input voltage is dropped
across two resistors. The hot leg of the 120V is tied to a 33k
resistor, which is tied to a 1k resistor, and the 1k is tied to the
neutral. Now, from the connection point of the two resistors, place a
diode which is in series with the contact switch for the light
sensor. So one leg of the light sensor contact will be on the diode.
The other leg of the light sensor contact will go to the high side of
a 5V relay coil. On the other side of the relay coil, place a cap and
resistor in parallel. The other legs of the resistor and capacitor
will be tied to neutral. The light will turn on until the cap is
charged to the point that it doesn't allow current through the relay
coil. This timing is dependent on the cap size and on the 33k
resistor (which is of course adjustable). The resistor which is in
parallel with the cap allows a discharge path. But the resistor has
to be large enough to limit the current through the relay coil. The
coil I'm talking about is a little Omron 5G series (about $2.00) and
it requires somewhere around 5mA to operate. Anyway, this will work.
But you'll have to mess around with the values. Good luck.

 

[Ron D.]

On Mar 28, 4:26 pm, "David" <some...@somewhere.com> wrote:

"David Nebenzahl" <nob...@but.us.chickens> wrote in message

news:49ce65a0$0$29745$822641b3@news.adtechcomputers.com...

On 3/27/2009 3:55 PM Tim spake thus:

OK, so I'm trying to come up with a simple (maybe even
elegant) solution to a simple problem. Have an idea I
want to run by y'all.

Function:  person has a motion-detector light installed
in their home. They want a buzzer/bell/annunciator of
some kind to go off *momentarily* whenever the light is
activated.

Here's my idea for the circuit:
http://www.geocities.com/bonezphoto/misc/One-shotBell.gif

OK, so a lot of issues here deal with the AC power being
detected and transferred to something useful. I did a
simple data logger for my well pump (URL:
http://personal.nbnet.nb.ca/snowowl/DataRecorder.html),
that had to deal 220V being sensed. I used a cheap little
cell phone / palm pilot charger that was universal
110/220 50/60hz and wired it parallel with the motor
leads. This gave me a nice 5 volts when the power was
applied to the pump, so I could log it's on cycles. You
still have to wire it up the the light, so that's a
danger here as well. Dealing with AC mains wiring, there
always a need for extra safety.

Thanks for your reply.

Unfortunately, your solution, while interesting, misses
one of the requirements of the whole deal: it needs to
operate the bell/chime/annunciator *momentarily*, not
continuously.

Why not take a crack at calculating the values of the
components and post your final circuit here. That way we
will get a good idea of how adept you are at circuit design.
I would still recommend putting R3 across C2 rather than C1
as per my original suggestion. That insures the drive to the
transistor truly goes to zero after some amount of time.

David

What you can do is purchase a Delay-On-Make block from www.ssac.com.

I already have a wireless motion detector that has that option.
Buzzer/and or outlet.
I don't use it that way. I have the dector mounted inside and the
receiver connected to a 7 W bulb.

 

[David Nebenzahl]

On 3/31/2009 4:57 AM Andy spake thus:

On Mar 28, 1:00 pm, David Nebenzahl <nob...@but.us.chickens> wrote:

(famous last words, "simple circuit" ...)

OK, so I'm trying to come up with a simple (maybe even elegant) solution
to a simple problem. Have an idea I want to run by y'all.

Function: person has a motion-detector light installed in their home.
They want a buzzer/bell/annunciator of some kind to go off *momentarily*
whenever the light is activated.

Here's my idea for the circuit:
http://www.geocities.com/bonezphoto/misc/One-shotBell.gif

First of all, I think that figuring things out is exactly what these
forums are for.

Thank you. That's what I think they're for as well.

I think your circuit is too complicated. I do this kind of circuit
all the time, but I usually use digital components and/ or
comparators, microprocessors, etc. But I like your idea of using the
RC charge cycle.

Thanks again.

My version of your circuit includes a small DC
relay. Let me try to explain it, since I'm not educated enough to
figure out how to post a drawing. The 120V input voltage is dropped
across two resistors. The hot leg of the 120V is tied to a 33k
resistor, which is tied to a 1k resistor, and the 1k is tied to the
neutral. Now, from the connection point of the two resistors, place a
diode which is in series with the contact switch for the light
sensor. So one leg of the light sensor contact will be on the diode.
The other leg of the light sensor contact will go to the high side of
a 5V relay coil. On the other side of the relay coil, place a cap and
resistor in parallel. The other legs of the resistor and capacitor
will be tied to neutral.

Great--another entry in the contest!

I've drawn what I think you just described:
http://www.geocities.com/bonezphoto/misc/One-shotBell3.gif

Is that what you had in mind? Notice I added the snubber diode across
the relay coil that the other David had asked for earlier.

So now *I* get to critique *your* circuit:

1. While the diode is needed to provide (pulsating) DC to charge the
capacitor, I don't think the motion sensor is going to like DC; I think
it wants AC. So that may make this not work at all.

2. Not sure why you have a voltage divider (the 33k and 1k resistors)
across the line, rather than just using the 33k resistor in series with
the diode/relay/capacitor chain; why the 1K resistor? You realize that
those resistors are going to draw power from the line all the time,
right? And where did you some up with those values?

3. And of course this still leaves the question of the values for what
I've labeled as "R" and "C", the components that provide the delay. I
wonder if someone could be so good as to take a guess at them, and,
better yet, tell us how to calculate them (yes, I know, you need to know
the inductance and resistance of the relay coil).

Not knocking your design, mind you (which, now that you see it, is
really *not* all that simple); just trying to learn something, which is
the object of this whole exercise.


--
Made From Pears: Pretty good chance that the product is at least
mostly pears.
Made With Pears: Pretty good chance that pears will be detectable in
the product.
Contains Pears: One pear seed per multiple tons of product.

(with apologies to Dorothy L. Sayers)

 

[Baron]

David Nebenzahl Inscribed thus:

On 3/31/2009 4:57 AM Andy spake thus:

On Mar 28, 1:00 pm, David Nebenzahl <nob...@but.us.chickens> wrote:

(famous last words, "simple circuit" ...)

OK, so I'm trying to come up with a simple (maybe even elegant)
solution to a simple problem. Have an idea I want to run by y'all.

Function: person has a motion-detector light installed in their
home. They want a buzzer/bell/annunciator of some kind to go off
*momentarily* whenever the light is activated.

Here's my idea for the circuit:
http://www.geocities.com/bonezphoto/misc/One-shotBell.gif

First of all, I think that figuring things out is exactly what these
forums are for.

Thank you. That's what I think they're for as well.

I think your circuit is too complicated. I do this kind of circuit
all the time, but I usually use digital components and/ or
comparators, microprocessors, etc. But I like your idea of using the
RC charge cycle.

Thanks again.

My version of your circuit includes a small DC
relay. Let me try to explain it, since I'm not educated enough to
figure out how to post a drawing. The 120V input voltage is dropped
across two resistors. The hot leg of the 120V is tied to a 33k
resistor, which is tied to a 1k resistor, and the 1k is tied to the
neutral. Now, from the connection point of the two resistors, place
a diode which is in series with the contact switch for the light
sensor. So one leg of the light sensor contact will be on the diode.
The other leg of the light sensor contact will go to the high side of
a 5V relay coil. On the other side of the relay coil, place a cap
and
resistor in parallel. The other legs of the resistor and capacitor
will be tied to neutral.

Great--another entry in the contest!

I've drawn what I think you just described:
http://www.geocities.com/bonezphoto/misc/One-shotBell3.gif

Is that what you had in mind? Notice I added the snubber diode across
the relay coil that the other David had asked for earlier.

So now *I* get to critique *your* circuit:

1. While the diode is needed to provide (pulsating) DC to charge the
capacitor, I don't think the motion sensor is going to like DC; I
think it wants AC. So that may make this not work at all.

2. Not sure why you have a voltage divider (the 33k and 1k resistors)
across the line, rather than just using the 33k resistor in series
with the diode/relay/capacitor chain; why the 1K resistor? You realize
that those resistors are going to draw power from the line all the
time, right? And where did you some up with those values?

3. And of course this still leaves the question of the values for what
I've labeled as "R" and "C", the components that provide the delay. I
wonder if someone could be so good as to take a guess at them, and,
better yet, tell us how to calculate them (yes, I know, you need to
know the inductance and resistance of the relay coil).

The value of the inductance of the relay coil is not needed for
calculating the delay time. Just the coil resistance !

Not knocking your design, mind you (which, now that you see it, is
really *not* all that simple); just trying to learn something, which
is the object of this whole exercise.

--
Best Reagrds:
Baron.

 

[Andy]

On Mar 31, 6:43 pm, David Nebenzahl <nob...@but.us.chickens> wrote:

On 3/31/2009 4:57 AM Andy spake thus:



On Mar 28, 1:00 pm, David Nebenzahl <nob...@but.us.chickens> wrote:

(famous last words, "simple circuit" ...)

OK, so I'm trying to come up with a simple (maybe even elegant) solution
to a simple problem. Have an idea I want to run by y'all.

Function:  person has a motion-detector light installed in their home.
They want a buzzer/bell/annunciator of some kind to go off *momentarily*
whenever the light is activated.

Here's my idea for the circuit:
http://www.geocities.com/bonezphoto/misc/One-shotBell.gif

First of all, I think that figuring things out is exactly what these
forums are for.

Thank you. That's what I think they're for as well.

I think your circuit is too complicated. I do this kind of circuit
all the time, but I usually use digital components and/ or
comparators, microprocessors, etc. But I like your idea of using the
RC charge cycle.

Thanks again.

My version of your circuit includes a small DC
relay.  Let me try to explain it, since I'm not educated enough to
figure out how to post a drawing.  The 120V input voltage is dropped
across two resistors.  The hot leg of the 120V is tied to a 33k
resistor, which is tied to a 1k resistor, and the 1k is tied to the
neutral.  Now, from the connection point of the two resistors, place a
diode which is in series with the contact switch for the light
sensor.  So one leg of the light sensor contact will be on the diode.
The other leg of the light sensor contact will go to the high side of
a 5V relay coil.  On the other side of the relay coil, place a cap and
resistor in parallel.  The other legs of the resistor and capacitor
will be tied to neutral.

Great--another entry in the contest!

I've drawn what I think you just described:http://www.geocities.com/bonezphoto/misc/One-shotBell3.gif

Is that what you had in mind? Notice I added the snubber diode across
the relay coil that the other David had asked for earlier.

So now *I* get to critique *your* circuit:

1. While the diode is needed to provide (pulsating) DC to charge the
capacitor, I don't think the motion sensor is going to like DC; I think
it wants AC. So that may make this not work at all.

2. Not sure why you have a voltage divider (the 33k and 1k resistors)
across the line, rather than just using the 33k resistor in series with
the diode/relay/capacitor chain; why the 1K resistor? You realize that
those resistors are going to draw power from the line all the time,
right? And where did you some up with those values?

3. And of course this still leaves the question of the values for what
I've labeled as "R" and "C", the components that provide the delay. I
wonder if someone could be so good as to take a guess at them, and,
better yet, tell us how to calculate them (yes, I know, you need to know
the inductance and resistance of the relay coil).

Not knocking your design, mind you (which, now that you see it, is
really *not* all that simple); just trying to learn something, which is
the object of this whole exercise.

--
Made From Pears: Pretty good chance that the product is at least
mostly pears.
Made With Pears: Pretty good chance that pears will be detectable in
the product.
Contains Pears:  One pear seed per multiple tons of product.

(with apologies to Dorothy L. Sayers)

I have used this circuit many times (without the relay) because it
will output a pretty stable DC signal at right around 5-6V. It works
because the charge cycle is much faster than the discharge cycle. The
resistor values are chosen to make sure that your DC output is
compatible with TTL, or a 5V logic input. This is a quick,
inexpensive circuit which I have used for monitoring motor states.
But, in this application, I have to say that it probably won't work.
It will turn on the light, but it will happen so fast as to be
invisible. The only way to make this work is to have a HUGE
capacitor.

 

[Baron]

David Nebenzahl wrote:

(famous last words, "simple circuit" ...)

Did you have a go with any of the suggestions ?

--
Best Regards:
Baron.