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dcooper

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Posts: 2
Posted Reply with quote  #1 
I'm looking at K126 - Sound Activated Relay Switch but have a couple
of questions.

I'd like to use it to turn on a sprinkler system which requires 24
volt AC power.  Would it be possible to modify the kit to operate at
the same power?

I'm also interested in having the switch come on immediately and stay
on for about 30 seconds.  I think that means I just need to change C2
& R5 as in the second half of the notes from the manual I've pasted
below.  Can you confirm this?

"The off delay time may be adjusted by varying R3 and R4.
Reducing R3 will result in a longer release time.

You could change the release time constant (C2 & R5) to
say 30 seconds and use the VOX as a light switch with
this delay time before turning off. Increase C2 to say 10u
and R3 to 3M3."

Thanks,

Dwayne
Frank

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Posts: 1,905
Posted Reply with quote  #2 
You would have to add a 12VDC power supply module that would take the 24VAC as input and produce a regulated 12VDC output. You could use a K60 kit for that job. All components are supplied - all you need to do is add a 12V regulator IC, a 7812 and possibly a heatsink.
dcooper

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Posts: 2
Posted Reply with quote  #3 
Thanks Frank -- I see how that would work.  One other question if you don't mind.   The instructions say to change  "Increase C2 to say 10u" -- do you know what type of capacitor that refers to?  I don't know much about electronic components and there seem to be different types and voltages.

Dwayne
Frank

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Posts: 1,905
Posted Reply with quote  #4 
It refers to a 10uF 16V (or 25V) electrolytic capacitor.
jkftl

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Posts: 2
Posted Reply with quote  #5 
How do I modify this device to detect only low-frequencies under 100Hz, closing the relay for 1-5 seconds, then opening and waiting de-energized for the next event?  I sense that changes are trivial.  I am ready to build two kits.  Please advise.
 
The purpose is to detect high-volume, offensive 'boom-box' sounds, energizing a screeching police siren.  Also might work on 'Harley' exhaust sound.  I like the 12V source, same as the siren.  Variable sensitivity is essential.
 
Frank

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Posts: 1,905
Posted Reply with quote  #6 
Capacitor C4 is used to reduce the high frequency response. I would suggest increasing that value until you get a result.

Difficult to determine the value - more a 'trial and error' approach. I would start with 1uF and increase from there.
jkftl

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Posts: 2
Posted Reply with quote  #7 
Thanks, Frank:
I will dig through my collection when I receive the kit.  Life for us has become more difficult with the demise of R/S.  [wink]:-(
John K.
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