(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/...e-shotBell.gif

First of all, please don't laugh at this. I am *not* a double-E or in
any way an electronics expert. Also keep in mind that this is the
farthest thing from a mil-spec application. It's just for fun; no life
support medical devices will depend on it.

I'd like to know the following:

1. Will this circuit even work?
1a. Will it work but end up destroying one or more components?
2. Is there a simpler way of accomplishing this task?
3. If it'll work, what are the right component values?

Explanation:

D1 is a half-wave rectifier. C2 filters the DC to produce more-or-less
ripple-free current. C1 provides the momentary "on" signal, by charging,
then "shutting down" when charged (sized according to RC time constant
to provide the desired "on" time). R2 and R3 form a voltage divider to
supply the appropriate base voltage to Q1. R1 acts as a voltage divider
in series with the load to supply the appropriate output voltage. (I
chose 24 volts DC arbitrarily; it might be less, probably not more.)

Component sizing:

R1 would obviously have to be large enough (in terms of power capacity)
to handle the load. The load would probably have a minimal current draw.
And since it would only be "on" momentarily, R1 could probably be a bit
undersized without worrying about damage.

Q1 would also need to be large enough to handle the load. I'm thinking a
common TO-220 type might work fine.

R2 & R3 could be small 1/8 watters.

OK, have at it. Rip 'er apart!


--
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)

On Tue, 24 Mar 2009 13:39:59 -0800, David Nebenzahl
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/...e-shotBell.gif

First of all, please don't laugh at this. I am *not* a double-E or in
any way an electronics expert. Also keep in mind that this is the
farthest thing from a mil-spec application. It's just for fun; no life
support medical devices will depend on it.

I'd like to know the following:

1. Will this circuit even work?
1a. Will it work but end up destroying one or more components?
2. Is there a simpler way of accomplishing this task?
3. If it'll work, what are the right component values?

Explanation:

D1 is a half-wave rectifier. C2 filters the DC to produce more-or-less
ripple-free current. C1 provides the momentary "on" signal, by charging,
then "shutting down" when charged (sized according to RC time constant
to provide the desired "on" time). R2 and R3 form a voltage divider to
supply the appropriate base voltage to Q1. R1 acts as a voltage divider
in series with the load to supply the appropriate output voltage. (I
chose 24 volts DC arbitrarily; it might be less, probably not more.)

Component sizing:

R1 would obviously have to be large enough (in terms of power capacity)
to handle the load. The load would probably have a minimal current draw.
And since it would only be "on" momentarily, R1 could probably be a bit
undersized without worrying about damage.

Q1 would also need to be large enough to handle the load. I'm thinking a
common TO-220 type might work fine.

R2 & R3 could be small 1/8 watters.

OK, have at it. Rip 'er apart!

I thibk you may want to check the orientation od D1.

Based on that, this might be safer:

Go to http://www.x10.com/products/pr511_ed_deal.html

Buy 2 motion sensor lights with an audio alert for $70.

Replace existing motion sensor light.

Plug in audio alert device.

Done.

On Mar 24, 2:39*pm, David Nebenzahl wrote:
(famous last words, "simple circuit" ...)


(famous last words, "what does this post have to do with electronics
repair"...)

(famous last words, "what does this post
have to do with electronics repair"...)

A lot... if the circuit damages something.

About 50 years ago, MAD ran a parody titled "Beatnik Magazine". One of its
contents was a photo of a middle-class family, watching TV in the living
room, with the caption "What's wrong with this picture?" The answer was
"Like, man, /everything/ is wrong with this picture."

That pretty applies to the circuit. I see what you're trying to do, but
you're going to get two exploded caps (at least), and possibly a small fire.

Take the other poster's advice. Buy a second detector and plug a 120V alarm
of some sort where the lamp goes. If the one you have an handle enough
current, you could always stick a plug adapter in the lamp socket.

"William Sommerwerck" wrote in
message ...
(famous last words, "what does this post
have to do with electronics repair"...)

A lot... if the circuit damages something.

About 50 years ago, MAD ran a parody titled "Beatnik
Magazine". One of its
contents was a photo of a middle-class family, watching TV
in the living
room, with the caption "What's wrong with this picture?"
The answer was
"Like, man, /everything/ is wrong with this picture."

That pretty applies to the circuit. I see what you're
trying to do, but
you're going to get two exploded caps (at least), and
possibly a small fire.

Take the other poster's advice. Buy a second detector and
plug a 120V alarm
of some sort where the lamp goes. If the one you have an
handle enough
current, you could always stick a plug adapter in the lamp
socket.

Actually the circuit is not all that unworkable. Some
suggestions and comments:

1) Diode D1 is backwards;
2) You need a resistor in series with D1 to limit in-rush
current;
3) There is no discharge path for C1. A high value resistor
across C2 can fix that;
4) What do expect to place across the terminals labeled 24
VDC? The voltage there may have no relation to 24 volts.

Further suggestions contingent upon knowing what is at the
24 VDC connection.

David

On 3/25/2009 5:24 AM David spake thus:

Actually the circuit is not all that unworkable. Some
suggestions and comments:

1) Diode D1 is backwards;
2) You need a resistor in series with D1 to limit in-rush
current;
3) There is no discharge path for C1. A high value resistor
across C2 can fix that;
4) What do expect to place across the terminals labeled 24
VDC? The voltage there may have no relation to 24 volts.

Further suggestions contingent upon knowing what is at the
24 VDC connection.

Thank you for not automatically dismissing the whole thing out of hand,
as other respondents obviously did. Not helpful.

OK, answers:

1. Yeah, it's a *drawing* error. I can still not remember which way is
which, graphically speaking, for the life of me. When I actually build
stuff I check and double-check diode anode-cathode connections, and
haven't gotten it wrong once. I guess I just need a good mnemonic to
remember which way the damn arrow points.

2. OK; I presume this needs to be the same size (power capacity) as the
resistor in series with the load, right?

3. OK.

4, 5: The load would be a small annunciator device: a doorbell, chime or
other sound-generating device, *probably* operating at 18-24 volts. I'm
guessing current draw would be in the low hundreds of mA, certainly less
than half an amp. Does that help?


--
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)

Further suggestions contingent upon knowing what is at the
24 VDC connection.

Thank you for not automatically dismissing the whole thing out
of hand, as other respondents obviously did. Not helpful.

What are we supposed to do? Be a free design service for someone with little
understanding of electronics?

I can see what's going to happen. You're going to build something, and when
it doesn't work, bring it back here over and over for troubleshooting
assistance.

This is not the way to learn electronics Find some books on electronics and
start reading.. Buy one of those 100-in-1 lab kits and have some fun.


Let me give a parallel example. Suppose you'd written the first chapter of a
crappy novel. Would you expect other people to guide you through the process
of editing it, and teaching you how to write, simply because they have
nothing better to do with their time?

On 3/25/2009 5:24 AM David spake thus:

Actually the circuit is not all that unworkable. Some
suggestions and comments:

Check the updated schematic, incorporating your suggestions:
http://www.geocities.com/bonezphoto/...e-shotBell.gif

Let me know what you think.


--
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)

"David Nebenzahl" wrote in message
s.com...
On 3/25/2009 5:24 AM David spake thus:

Actually the circuit is not all that unworkable. Some
suggestions and comments:

Check the updated schematic, incorporating your
suggestions:
http://www.geocities.com/bonezphoto/...e-shotBell.gif

Let me know what you think.


--
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)

OK the circuit is better. R3 will also discharge C2 which is
also necessary to allow the circuit to start another cycle.
The surge resistor should be in the low 10s of ohms and
probably about a watt. If the load is in the 100-200mA range
than just size the R2 resistor as needed. Remember that the
voltage across C2 will be close to 150v. I would put a Zener
diode across the load to prevent voltages going above what
your annunciate device can handle safely. Remember that this
entire circuit is at line voltage and anything connected can
be a severe shock hazard.

David

On 3/25/2009 5:24 AM David spake thus:

Actually the circuit is not all that unworkable. Some
suggestions and comments:

1) Diode D1 is backwards;
2) You need a resistor in series with D1 to limit in-rush
current;
3) There is no discharge path for C1. A high value resistor
across C2 can fix that;
4) What do expect to place across the terminals labeled 24
VDC? The voltage there may have no relation to 24 volts.

Further suggestions contingent upon knowing what is at the
24 VDC connection.

Thank you for not automatically dismissing the whole thing out of hand,
as other respondents obviously did. Not helpful.

OK, answers:

1. Yeah, it's a *drawing* error. I can still not remember which way is
which, graphically speaking, for the life of me. When I actually build
stuff I check and double-check diode anode-cathode connections, and
haven't gotten it wrong once. I guess I just need a good mnemonic to
remember which way the damn arrow points.

2. OK; I presume this needs to be the same size (power capacity) as the
resistor in series with the load, right?

3. OK.

4, 5: The load would be a small annunciator device: a doorbell, chime or
other sound-generating device, *probably* operating at 18-24 volts. I'm
guessing current draw would be in the low hundreds of mA, certainly less
than half an amp. Does that help?


-- 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)

On 3/25/2009 5:24 AM David spake thus:

Actually the circuit is not all that unworkable. Some
suggestions and comments:

1) Diode D1 is backwards;
2) You need a resistor in series with D1 to limit in-rush
current;
3) There is no discharge path for C1. A high value resistor
across C2 can fix that;
4) What do expect to place across the terminals labeled 24
VDC? The voltage there may have no relation to 24 volts.

Further suggestions contingent upon knowing what is at the
24 VDC connection.

Thank you for not automatically dismissing the whole thing out of hand,
as other respondents obviously did. Not helpful.

OK, answers:

1. Yeah, it's a *drawing* error. I can still not remember which way is
which, graphically speaking, for the life of me. When I actually build
stuff I check and double-check diode anode-cathode connections, and
haven't gotten it wrong once. I guess I just need a good mnemonic to
remember which way the damn arrow points.

2. OK; I presume this needs to be the same size (power capacity) as the
resistor in series with the load, right?

3. OK.

4, 5: The load would be a small annunciator device: a doorbell, chime or
other sound-generating device, *probably* operating at 18-24 volts. I'm
guessing current draw would be in the low hundreds of mA, certainly less
than half an amp. Does that help?


--
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)

On Mar 25, 1:47*pm, David Nebenzahl wrote:

Thank you for not automatically dismissing the whole thing out of hand,
as other respondents obviously did. Not helpful.


and thank you for not multiple posting
and thank you for not multiple posting
and thank you for not multiple posting
and thank you for not multiple posting
and thank you for not multiple posting
and thank you for not multiple postilg

"David Nebenzahl" schreef in bericht
s.com...
(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/...e-shotBell.gif

First of all, please don't laugh at this. I am *not* a double-E or in any
way an electronics expert. Also keep in mind that this is the farthest
thing from a mil-spec application. It's just for fun; no life support
medical devices will depend on it.

I'd like to know the following:

1. Will this circuit even work?
1a. Will it work but end up destroying one or more components?
2. Is there a simpler way of accomplishing this task?
3. If it'll work, what are the right component values?

Explanation:

D1 is a half-wave rectifier. C2 filters the DC to produce more-or-less
ripple-free current. C1 provides the momentary "on" signal, by charging,
then "shutting down" when charged (sized according to RC time constant to
provide the desired "on" time). R2 and R3 form a voltage divider to supply
the appropriate base voltage to Q1. R1 acts as a voltage divider in series
with the load to supply the appropriate output voltage. (I chose 24 volts
DC arbitrarily; it might be less, probably not more.)

Component sizing:

R1 would obviously have to be large enough (in terms of power capacity) to
handle the load. The load would probably have a minimal current draw. And
since it would only be "on" momentarily, R1 could probably be a bit
undersized without worrying about damage.

Q1 would also need to be large enough to handle the load. I'm thinking a
common TO-220 type might work fine.

R2 & R3 could be small 1/8 watters.

OK, have at it. Rip 'er apart!


--
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)

It will not work at all and it'll take half a course in electronics to
explain why. I'm too tired to write that course.

petrus bitbyter

On Tue, 24 Mar 2009 13:39:59 -0800, David Nebenzahl
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/...e-shotBell.gif

First of all, please don't laugh at this. I am *not* a double-E or in
any way an electronics expert. Also keep in mind that this is the
farthest thing from a mil-spec application. It's just for fun; no life
support medical devices will depend on it.

I'd like to know the following:

1. Will this circuit even work?
1a. Will it work but end up destroying one or more components?
2. Is there a simpler way of accomplishing this task?
3. If it'll work, what are the right component values?

Explanation:

D1 is a half-wave rectifier. C2 filters the DC to produce more-or-less
ripple-free current. C1 provides the momentary "on" signal, by charging,
then "shutting down" when charged (sized according to RC time constant
to provide the desired "on" time). R2 and R3 form a voltage divider to
supply the appropriate base voltage to Q1. R1 acts as a voltage divider
in series with the load to supply the appropriate output voltage. (I
chose 24 volts DC arbitrarily; it might be less, probably not more.)

Component sizing:

R1 would obviously have to be large enough (in terms of power capacity)
to handle the load. The load would probably have a minimal current draw.
And since it would only be "on" momentarily, R1 could probably be a bit
undersized without worrying about damage.

Q1 would also need to be large enough to handle the load. I'm thinking a
common TO-220 type might work fine.

R2 & R3 could be small 1/8 watters.

OK, have at it. Rip 'er apart!

Reversing D1 and providing a bleeder resistor across C2 have already
been mentioned. I have two further suggestions.

1. Either provide a diode to prevent the base of Q1 going too far
negative with respect to it's emitter or size the bleeder resistor
(R4) so the time constant of C2-R4 is much greater than the time
constant of C1-R2+R3
2. Choose R1 to provide about a 140V drop across R1 at the buzzer's
rated current. Place a zener diode across the 24VDC terminals to
prevent excessive current flow through the buzzer.

Contrary to what several nay-sayers have expressed, this exercise has
a LOT to do with electronics repair. Any fool can keep replacing
components until he finds the bad one. The successful tech will be
able to analyse a circuit and make meaningful tests to identfy the
failing part.

NOW your next exercise is to identify the values for these components.


PlainBill

On 3/25/2009 10:24 AM PlainBill spake thus:

Contrary to what several nay-sayers have expressed, this exercise has
a LOT to do with electronics repair. Any fool can keep replacing
components until he finds the bad one. The successful tech will be
able to analyse a circuit and make meaningful tests to identfy the
failing part.

Thank you. It's more than a little annoying being completely written off
as a clueless idiot simply because I reversed a diode's polarity *in a
schematic* (since corrected).

NOW your next exercise is to identify the values for these components.


I'd love to oblige you; unfortunately, I'm not yet at that level. I know
Ohm's law and some other basic stuff, but not enough about circuit
design to assign values with any confidence. I look forward to others
doing that. And someday, I intend to get a good basic electronics
textbook and seriously study it ...


--
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)

On Wed, 25 Mar 2009 18:01:12 -0800, David Nebenzahl
wrote:

On 3/25/2009 10:24 AM PlainBill spake thus:

Contrary to what several nay-sayers have expressed, this exercise has
a LOT to do with electronics repair. Any fool can keep replacing
components until he finds the bad one. The successful tech will be
able to analyse a circuit and make meaningful tests to identfy the
failing part.

Thank you. It's more than a little annoying being completely written off
as a clueless idiot simply because I reversed a diode's polarity *in a
schematic* (since corrected).

NOW your next exercise is to identify the values for these components.


I'd love to oblige you; unfortunately, I'm not yet at that level. I know
Ohm's law and some other basic stuff, but not enough about circuit
design to assign values with any confidence. I look forward to others
doing that. And someday, I intend to get a good basic electronics
textbook and seriously study it ...

Several comments on this circuit. First of all, it could work, but
would require significant improvements, some of which have already
been discussed. Rather than using a doorbell or chime, a Sonalert
could be used. In part this will depend on the sound level desired.

Second, some of the criticisms are valid. If you intend to do this as
a design exercise you can have fun designing it, but I would not
recommend building it. You are dealing with potentially lethal
voltages, and fairly expensive components to withstand those voltages.

IMHO, you are using the wrong approach. Over 30 years ago I built
something similar using a few small caps, a few resistors, a diode, a
speaker, and a 74C914 hex schmidt trigger. I used 4 AA cells to power
it, your application should use a 'wall wart' putting out 6VDC at 100
ma. I'd have to look up the specs, but a 555 timer would also do the
job.

PlainBill

On 3/26/2009 9:21 AM PlainBill spake thus:

On Wed, 25 Mar 2009 18:01:12 -0800, David Nebenzahl
wrote:

On 3/25/2009 10:24 AM PlainBill spake thus:

Contrary to what several nay-sayers have expressed, this exercise has
a LOT to do with electronics repair. Any fool can keep replacing
components until he finds the bad one. The successful tech will be
able to analyse a circuit and make meaningful tests to identfy the
failing part.

Thank you. It's more than a little annoying being completely written off
as a clueless idiot simply because I reversed a diode's polarity *in a
schematic* (since corrected).

NOW your next exercise is to identify the values for these components.


I'd love to oblige you; unfortunately, I'm not yet at that level. I know
Ohm's law and some other basic stuff, but not enough about circuit
design to assign values with any confidence. I look forward to others
doing that. And someday, I intend to get a good basic electronics
textbook and seriously study it ...

Several comments on this circuit. First of all, it could work, but
would require significant improvements, some of which have already
been discussed. Rather than using a doorbell or chime, a Sonalert
could be used. In part this will depend on the sound level desired.

So what improvements would you suggest to the current circuit (after I
made the changes recommended earlier)? (Circuit at
http://www.geocities.com/bonezphoto/...e-shotBell.gif)

Second, some of the criticisms are valid. If you intend to do this as
a design exercise you can have fun designing it, but I would not
recommend building it. You are dealing with potentially lethal
voltages, and fairly expensive components to withstand those voltages.

To be honest, I think it's more fun designing things like this that will
operate "directly" off line voltage (i.e., without a transformer). One
of the criteria of this whole deal was to avoid the use of a transformer.

And in defense of that, there are tons of things in use every day that
operate just this way. Latest example I found were a bunch of electric
staple guns a neighbor gave me that operated directly off 120 volts,
firing a solenoid through a capacitor.

If I were to actually build this, I'm confident I could do it safely--at
least as safely as those staple guns, which have UL, CSA, etc., compliance.

And what components would be expensive? Seems to me the most expensive
part would be the transistor, or possibly the two power resistors, but
even those aren't terribly pricey.

IMHO, you are using the wrong approach. Over 30 years ago I built
something similar using a few small caps, a few resistors, a diode, a
speaker, and a 74C914 hex schmidt trigger. I used 4 AA cells to power
it, your application should use a 'wall wart' putting out 6VDC at 100
ma. I'd have to look up the specs, but a 555 timer would also do the
job.

Could do, but see above.


--
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)

On Mar 26, 6:12*pm, David Nebenzahl wrote:
On 3/26/2009 9:21 AM PlainBill spake thus:





On Wed, 25 Mar 2009 18:01:12 -0800, David Nebenzahl
wrote:

On 3/25/2009 10:24 AM PlainBill spake thus:

Contrary to what several nay-sayers have expressed, this exercise has
a LOT to do with electronics repair. *Any fool can keep replacing
components until he finds the bad one. *The successful tech will be
able to analyse a circuit and make meaningful tests to identfy the
failing part.

Thank you. It's more than a little annoying being completely written off
as a clueless idiot simply because I reversed a diode's polarity *in a
schematic* (since corrected).

NOW your next exercise is to identify the values for these components..


I'd love to oblige you; unfortunately, I'm not yet at that level. I know
Ohm's law and some other basic stuff, but not enough about circuit
design to assign values with any confidence. I look forward to others
doing that. And someday, I intend to get a good basic electronics
textbook and seriously study it ...

Several comments on this circuit. *First of all, it could work, but
would require significant improvements, some of which have already
been discussed. *Rather than using a doorbell or chime, a Sonalert
could be used. *In part this will depend on the sound level desired.

So what improvements would you suggest to the current circuit (after I
made the changes recommended earlier)? (Circuit athttp://www.geocities.com/bonezphoto/misc/One-shotBell.gif)

Second, some of the criticisms are valid. *If you intend to do this as
a design exercise you can have fun designing it, but I would not
recommend building it. *You are dealing with potentially lethal
voltages, and fairly expensive components to withstand those voltages.

To be honest, I think it's more fun designing things like this that will
operate "directly" off line voltage (i.e., without a transformer). One
of the criteria of this whole deal was to avoid the use of a transformer.

And in defense of that, there are tons of things in use every day that
operate just this way. Latest example I found were a bunch of electric
staple guns a neighbor gave me that operated directly off 120 volts,
firing a solenoid through a capacitor.

If I were to actually build this, I'm confident I could do it safely--at
least as safely as those staple guns, which have UL, CSA, etc., compliance.

And what components would be expensive? Seems to me the most expensive
part would be the transistor, or possibly the two power resistors, but
even those aren't terribly pricey.

IMHO, you are using the wrong approach. *Over 30 years ago I built
something similar using a few small caps, a few resistors, a diode, a
speaker, and a 74C914 hex schmidt trigger. *I used 4 AA cells to power
it, your application should use a 'wall wart' putting out 6VDC at 100
ma. *I'd have to look up the specs, but a 555 timer would also do the
job.

Could do, but see above.

--
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)

And a relay won't do what you want? In theory, IF you get the
component values right AND the hot / neutral are as expected it COULD
work but I CERTAINLY would NOT allow that kind of mess in my house.

If you're going to dabble, do it at low voltages and transformer
isolated so you don't blow up stuff OR yourself.

Sorry to rain on your parade but at least you're alive to be ****ed at
me.

G²

David Nebenzahl Inscribed thus:

To be honest, I think it's more fun designing things like this that
will operate "directly" off line voltage (i.e., without a
transformer). One of the criteria of this whole deal was to avoid the
use of a transformer.

And in defense of that, there are tons of things in use every day that
operate just this way. Latest example I found were a bunch of electric
staple guns a neighbor gave me that operated directly off 120 volts,
firing a solenoid through a capacitor.

If I were to actually build this, I'm confident I could do it
safely--at least as safely as those staple guns, which have UL, CSA,
etc., compliance.

With all due respect I doubt it !

If you really look closely at the sort of products you mention, and I
could mention many more, they are all constructed in such a way that it
would be very difficult if not impossible for you to be able to touch
any part that would allow you to come into contact with the mains !

By doing what you are wanting to do, and I am not saying "Don't", you
are potentially putting yourself and others at risk of electric shock,
not to mention any other possible hazards.

I personally would want to ensure that I didn't introduce any potential
hazard that could endanger my family, myself or any visitors !

A small relay would do what you want and provide isolation from the
mains supply.

--
Best Reagrds:
Baron.

On Thu, 26 Mar 2009 17:12:00 -0800, David Nebenzahl
wrote:

On 3/26/2009 9:21 AM PlainBill spake thus:

On Wed, 25 Mar 2009 18:01:12 -0800, David Nebenzahl
wrote:

On 3/25/2009 10:24 AM PlainBill spake thus:

Contrary to what several nay-sayers have expressed, this exercise has
a LOT to do with electronics repair. Any fool can keep replacing
components until he finds the bad one. The successful tech will be
able to analyse a circuit and make meaningful tests to identfy the
failing part.

Thank you. It's more than a little annoying being completely written off
as a clueless idiot simply because I reversed a diode's polarity *in a
schematic* (since corrected).

NOW your next exercise is to identify the values for these components.


I'd love to oblige you; unfortunately, I'm not yet at that level. I know
Ohm's law and some other basic stuff, but not enough about circuit
design to assign values with any confidence. I look forward to others
doing that. And someday, I intend to get a good basic electronics
textbook and seriously study it ...

Several comments on this circuit. First of all, it could work, but
would require significant improvements, some of which have already
been discussed. Rather than using a doorbell or chime, a Sonalert
could be used. In part this will depend on the sound level desired.

So what improvements would you suggest to the current circuit (after I
made the changes recommended earlier)? (Circuit at
http://www.geocities.com/bonezphoto/...e-shotBell.gif)

You must add surge supression if you are using an inductive load.
Without it, the pulse generated when the transistor turns off will
eventually destroy it.

Second, some of the criticisms are valid. If you intend to do this as
a design exercise you can have fun designing it, but I would not
recommend building it. You are dealing with potentially lethal
voltages, and fairly expensive components to withstand those voltages.

To be honest, I think it's more fun designing things like this that will
operate "directly" off line voltage (i.e., without a transformer). One
of the criteria of this whole deal was to avoid the use of a transformer.

And in defense of that, there are tons of things in use every day that
operate just this way. Latest example I found were a bunch of electric
staple guns a neighbor gave me that operated directly off 120 volts,
firing a solenoid through a capacitor.

If I were to actually build this, I'm confident I could do it safely--at
least as safely as those staple guns, which have UL, CSA, etc., compliance.

And what components would be expensive? Seems to me the most expensive
part would be the transistor, or possibly the two power resistors, but
even those aren't terribly pricey.

Cost would depend on the nature of the load. If you are using a
Sonalert the load would be under .04A.

On the other hand, if you are using a chime the load will be higher,
and using a doorbell REALLY opens a can of worms. I think you had
better expect a load of .5A, and one heck of an inductive kick as the
transistor turns off. The typical doorbell is designed to operate on
about 15VAC. I would expect rater short contact life if you run it
off DC.


IMHO, you are using the wrong approach. Over 30 years ago I built
something similar using a few small caps, a few resistors, a diode, a
speaker, and a 74C914 hex schmidt trigger. I used 4 AA cells to power
it, your application should use a 'wall wart' putting out 6VDC at 100
ma. I'd have to look up the specs, but a 555 timer would also do the
job.

Could do, but see above.

PlainBill

David Nebenzahl wrote:
I'd love to oblige you; unfortunately, I'm not yet at that level. I know
Ohm's law and some other basic stuff, but not enough about circuit
design to assign values with any confidence. I look forward to others
doing that. And someday, I intend to get a good basic electronics
textbook and seriously study it ...

"The Art of Electronics" by Horowitz & Hill. You'll save a fortune if
you buy a used student copy.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

In article m,
kens 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/...e-shotBell.gif

First of all, please don't laugh at this. I am *not* a double-E or in
any way an electronics expert. Also keep in mind that this is the
farthest thing from a mil-spec application. It's just for fun; no life
support medical devices will depend on it.

I'd like to know the following:

1. Will this circuit even work?
1a. Will it work but end up destroying one or more components?
2. Is there a simpler way of accomplishing this task?
3. If it'll work, what are the right component values?

Explanation:

D1 is a half-wave rectifier. C2 filters the DC to produce more-or-less
ripple-free current. C1 provides the momentary "on" signal, by charging,
then "shutting down" when charged (sized according to RC time constant
to provide the desired "on" time). R2 and R3 form a voltage divider to
supply the appropriate base voltage to Q1. R1 acts as a voltage divider
in series with the load to supply the appropriate output voltage. (I
chose 24 volts DC arbitrarily; it might be less, probably not more.)

Component sizing:

R1 would obviously have to be large enough (in terms of power capacity)
to handle the load. The load would probably have a minimal current draw.
And since it would only be "on" momentarily, R1 could probably be a bit
undersized without worrying about damage.

Q1 would also need to be large enough to handle the load. I'm thinking a
common TO-220 type might work fine.

R2 & R3 could be small 1/8 watters.

OK, have at it. Rip 'er apart!



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.

- Tim -

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

In article m,
kens 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/...e-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)

"David Nebenzahl" wrote in message
s.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/...e-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

On 3/28/2009 12:26 PM David spake thus:

"David Nebenzahl" wrote in message
s.com...

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/...e-shotBell.gif

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.

Hey, thanks for sticking with me. Check latest circuit incarnation at
http://www.geocities.com/bonezphoto/...e-shotBell.gif.

Component Value
-----------------------------
C1 100 uf/200 V.
C2 1 uf/100 V.
R1, R2 500 Ω, 2 W
R3 220 kΩ, 1/8 W
R4, R5 10 kΩ, 1/8 W
D1 1N4001
Q1 D1266 or equiv.

Rationale for values (assuming ~20 volt, 100 mA load):

C1: large enough to filter bulk of ripple
C2: sized for proper "on" time (WAG)
R1, R2: voltage divider to yield ~20 volts for load device;
calculations dictate 5 watt load, but since it's of short
duration, 2 w. should be sufficient
R3: bleeder (slow) for C1
R4, R5: this is also a WAG (wild-ass guess); see below
D1: 1A, 600 PIV
Q1: selected because I have these and have used them before.

OK, I admit that I do not know how to calculate those last 2 resistances
for proper biasing of Q1; so sue me. I do understanfd the general
principle of biasing; just never had the formal training to learn how to
calculate values to implement it. I'd appreciate your comments here, and
I'd be curious to know how far off my guesses were.

BTW, I misunderstood where you wanted the bleeder resistor.

So give me a grade on my work.


--
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)

"David Nebenzahl" wrote in message
s.com...
On 3/28/2009 12:26 PM David spake thus:

"David Nebenzahl" wrote in
message
s.com...

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/...e-shotBell.gif

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.

Hey, thanks for sticking with me. Check latest circuit
incarnation at
http://www.geocities.com/bonezphoto/...e-shotBell.gif.

Component Value
-----------------------------
C1 100 uf/200 V.
C2 1 uf/100 V.
R1, R2 500 Ω, 2 W
R3 220 kΩ, 1/8 W
R4, R5 10 kΩ, 1/8 W
D1 1N4001
Q1 D1266 or equiv.

Rationale for values (assuming ~20 volt, 100 mA load):

C1: large enough to filter bulk of ripple
C2: sized for proper "on" time (WAG)
R1, R2: voltage divider to yield ~20 volts for load
device;
calculations dictate 5 watt load, but since it's
of short
duration, 2 w. should be sufficient
R3: bleeder (slow) for C1
R4, R5: this is also a WAG (wild-ass guess); see below
D1: 1A, 600 PIV
Q1: selected because I have these and have used them
before.

OK, I admit that I do not know how to calculate those last
2 resistances for proper biasing of Q1; so sue me. I do
understanfd the general principle of biasing; just never
had the formal training to learn how to calculate values
to implement it. I'd appreciate your comments here, and
I'd be curious to know how far off my guesses were.

BTW, I misunderstood where you wanted the bleeder
resistor.

So give me a grade on my work.

So far the grade is not very good. The transistor is rated
at 60v. When the transistor is off it has to sustain the
full rectified voltage.of about 150v. The same is true of
C2. R3 is still in the wrong place. R5 should be much
smaller than R4 since Vbe will always be under a volt. R1,
R2 are close, but how sure are you that 20v will not
destroy the load? A better choice would be a smaller R1 and
larger R2 since the circuit as shown introduces a lot of C
to B feedback which will drastically slow down the turnoff
time and keep the transistor in a linear mode for longer
than necessary. Need load on time, and hfe of the transistor
you choose to calculate C2, R4, and R5.

Other prople replying have suggested either a transformer
isolated design or the use of a small relay and a simple
diode RC network to drive it. The relay is a good choice if
you can get the power to run the load elsewhere.

David

On Mar 28, 4:26*pm, "David" wrote:
"David Nebenzahl" wrote in message

s.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/...e-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 wrote:

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

In article m,
kens 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.

I think that a small sugar cube relay, diode, resistor and capacitor
will do the job !

--
Best Regards:
Baron.

On 3/28/2009 1:30 PM Baron spake thus:

David Nebenzahl wrote:

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

In article m,
kens 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.

I think that a small sugar cube relay, diode, resistor and capacitor
will do the job !

Circuit, pleeze?


--
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)

David Nebenzahl wrote:

On 3/28/2009 1:30 PM Baron spake thus:

David Nebenzahl wrote:

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

In article m,
kens 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.

I think that a small sugar cube relay, diode, resistor and capacitor
will do the job !

Circuit, pleeze?


Ok but excuse the ascii art.

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

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.

--
Best Regards:
Baron.

On Sat, 28 Mar 2009 11:00:45 -0800, David Nebenzahl
wrote:

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

In article m,
kens 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/...e-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.


Since you need 18-24vdc, instead of the hazard of components
directly connected to the powerline, use an approved AC adapter or
"wallwart" that would provide the necessary DC voltage. From the
output of the AC adapter, place a PTC (positive temperature
coefficient) thermistor in series with your load. It will be a bit
tricky to determine the right physical size and nominal resistance of
the thermistor, since you haven't specified the load.
When the adapter powers up, the thermistor will be cold, and will
run the "indicator" what ever that is. After the thermistor heats up,
it will reduce the current going to your device, hopefully to the
point where it won't be noticed. The "resetable fuses" work on this
idea, you could use one of them the same way, but you need to again
select based on current load, and power.
If you get it to work it's: simple
doesn't violate electrical safety
reliable
The disadvantage, is that once on, it needs some time to "reset"
(cool down). The thermistor does get hot, a poorly designed circuit
could get hot enough to be a problem.

There are relay circuits that do much the same, but I'd run them
off the ac adapter as well. (relay in series with large cap, operates
when cap charges up. cap was bleeder resistor in parallel so it
discharges prperly when power is removed). The relay circuit would be
straight forward to calculate the on time (a percentage of the time
constant).

I'd prefer you stick to quite low voltages (6-12v), to minimize any
risk of shock. Who knows how this circuit might be physically
implemented!

Paul G.

In article m,
kens says...
On 3/27/2009 3:55 PM Tim spake thus:

In article m,
kens 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/...e-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.



Perhaps you are not inventive enough. My idea was to get a voltage low
enough to be safe. 5 volts could be used to fire a simple one-shot
circuit when the light comes on.

- Tim -

On Mar 28, 1:00*pm, David Nebenzahl wrote:
On 3/27/2009 3:55 PM Tim spake thus:





In article m,
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/...e-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.

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

On Mar 28, 1:00 pm, David Nebenzahl 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/...e-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/...-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)

David Nebenzahl Inscribed thus:

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

On Mar 28, 1:00 pm, David Nebenzahl 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/...e-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/...-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.

On Mar 31, 6:43*pm, David Nebenzahl wrote:
On 3/31/2009 4:57 AM Andy spake thus:



On Mar 28, 1:00 pm, David Nebenzahl 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/...e-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/...-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.

On Mar 24, 2:39*pm, David Nebenzahl 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....

David Nebenzahl wrote:

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

Did you have a go with any of the suggestions ?

--
Best Regards:
Baron.