I thibk you may want to check the orientation od D1.
Based on that, this might be safer:
Go to
Buy 2 motion sensor lights with an audio alert for $70.
Replace existing motion sensor light.
Plug in audio alert device.
Done.
(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:
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:
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)
(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:
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:
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)
(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 news:gqbu7q$o6b$ snipped-for-privacy@news.motzarella.org...
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
"David Nebenzahl" schreef in bericht news:49c944ff$0$29984$ snipped-for-privacy@news.adtechcomputers.com...
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
Reversing D1 and providing a bleeder resistor across C2 have already been mentioned. I have two further suggestions.
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 5:24 AM David spake thus:
Thank you for not automatically dismissing the whole thing out of hand, as other respondents obviously did. Not helpful.
OK, answers:
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:
Check the updated schematic, incorporating your suggestions:
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)
On 3/25/2009 5:24 AM David spake thus:
Thank you for not automatically dismissing the whole thing out of hand, as other respondents obviously did. Not helpful.
OK, answers:
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:
Thank you for not automatically dismissing the whole thing out of hand, as other respondents obviously did. Not helpful.
OK, answers:
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)
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
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
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 1:55 PM Jeff Hackler spake thus:
Sorry 'bout that: for some reason, my posts haven't been "getting through" here lately (had to post the original message twice to have it show up here at all).
-- 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 10:24 AM PlainBill spake thus:
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).
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)
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:
So what improvements would you suggest to the current circuit (after I made the changes recommended earlier)? (Circuit at
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.
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)
f . w s
e.
rAnd 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 pissed at me.
G=B2
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