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Old 6th August 2003, 04:55 PM   #1
jaramke is offline jaramke  Kenya
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Question problems with a project i am working in

i am working on a project as part of my requirement for the degree BST electronics whereby i am supposed to construct a project and come up with a artwork and build the project to work as a final product. i selected a project entitled AUDIO AUTOSHUTOFF which is found in the following address :
home.maine.rr.com/randylinscott/project.htm
A february 2000 project.
i encountered a few problems during the breadboarding stage i kindly ask for assistance.
the problems are as follows.
1. the timer circuit is supposed to vary the time before shutoff but the project i breadboarded could not do this.
the project exhibited the following. the switching is working alright but initially when you turn on the project it will take about 2 minutes before it switches off but thereafter it will take about 30 seconds only.
2. the reset switches is not working
i kindly ask for assistance or if possible an alternative circuit that employs the same principle or close or similar to this so that i can be able to accomplish the requirement
thanks to you all for the anticipated help
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Old 7th August 2003, 10:15 AM   #2
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I have moved this to SS, you stand more chance of getting a reply there.
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Old 7th August 2003, 10:24 AM   #3
halojoy is offline halojoy  Sweden
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Default Re: problems with a project i am working in

Quote:
Originally posted by jaramke
A february 2000 project.
i encountered a few problems during the breadboarding stage i kindly ask for assistance.
the problems are as follows.

1. the timer circuit is supposed to vary the time before shutoff but the project i breadboarded could not do this.
the project exhibited the following. the switching is working alright but initially when you turn on the project it will take about 2 minutes before it switches off but thereafter it will take about 30 seconds only.

2. the reset switches is not working

i kindly ask for assistance or if possible an alternative circuit that employs the same principle or close or similar to this so that i can be able to accomplish the requirement
thanks to you all for the anticipated help
some information:
Here is link to project, jaramke mention

http://home.maine.rr.com/randylinscott/feb20.htm

here is Shutoff Circuit on the same page:
Click the image to open in full size.
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Old 7th August 2003, 10:32 AM   #4
halojoy is offline halojoy  Sweden
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Default Discharge of Timer Capacitor

When using big Timer Capacitators
you need something to discharge them when cicuit/switch is turned off.
This can be done via a suitable resistor and/or diode.

I see that the big 1000uF Cap, next to switch S3
has no such discharge feature.

Often used is a diode with reversed connection is used,
sometimes with a current limting resistor in series.
Anode of diode is connected to negative pol of Elyt-cap
and cathode to positive, eventually via a small resistor.
This will discharge the cap downto
the diode's conducting threshold, usually like 0.5V

I see that Q3 is supposed to be the discharger of Cap 1000uF.
But can only do so when s3 is closed,
and if signal is high to the base of transistor.
Can be things to check with a voltmeter. If it is properly discharging downto 0.xx Volt.

Can this do any good, or is there anything else wrong?
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Old 7th August 2003, 11:16 AM   #5
Keld is offline Keld  Sweden
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Hi
This is another project doing almost the same, but this is called "Signal Detecting Auto Power-On Unit": http://sound.westhost.com/project38.htm
But I think that, with some minor changes, it could be doing what "your project" is, or, is supposed to be, doing. In your project I would skip the triac and go for an all relay solution.

DVC Keld
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Old 7th August 2003, 11:57 AM   #6
halojoy is offline halojoy  Sweden
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Quote:
Originally posted by Keld
Hi
This is another project doing almost the same, but this is called "Signal Detecting Auto Power-On Unit": http://sound.westhost.com/project38.htm
But I think that, with some minor changes, it could be doing what "your project" is, or, is supposed to be, doing. In your project I would skip the triac and go for an all relay solution.

DVC Keld
I have to agree with Keld.
You should build another circuit.
It can be done much, much simpler. And with fully same functions.
There are a number of such samples to find around the web.
I have seen several different solutions.

This search result with Google gave 19 hits
for search: schematics audio "auto power on"

http://www.google.com/search?hl=en&i...=Google+Search
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