trigger shot by sound detection? - Script Writing - CHDK Forum
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trigger shot by sound detection?

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Offline bashir

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trigger shot by sound detection?
« on: 18 / March / 2011, 17:33:45 »
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Is there a script like motion detection that uses sound detection to trigger the shot. Could be used in complete darkness (which is what I want). Also could be used to give earlier warning of close approach e.g. start film before subject appears on screen.

cheers
Bashir
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Offline reyalp

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Re: trigger shot by sound detection?
« Reply #1 on: 18 / March / 2011, 18:22:32 »
Quote from: bashir on 18 / March / 2011, 17:33:45
Is there a script like motion detection that uses sound detection to trigger the shot. Could be used in complete darkness (which is what I want). Also could be used to give earlier warning of close approach e.g. start film before subject appears on screen.
Not currently possible, could be done in theory.
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Offline Microfunguy

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Re: trigger shot by sound detection?
« Reply #2 on: 18 / March / 2011, 18:37:45 »
Not a script, but can be done with some external electronics.
Basically, you have a flip-flop that is set by a remote pushbutton.
This initiates the capture sequence which is started but paused.
The sound is detected by a microphone and the flip-flop reset.

This has the same effect as releasing the switch and the photo is taken about 20msec later.
This can be done in full daylight if you wish and even with two cameras for stereo.
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Offline bashir

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Re: trigger shot by sound detection?
« Reply #3 on: 19 / March / 2011, 03:58:09 »
Ok. Thanks for the replies.
although an internal script would be neater looks more difficult. I guess additional power also needed for the flip-flop and microphone? Will look at that option.
Ta
Bashir
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Offline Microfunguy

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Re: trigger shot by sound detection?
« Reply #4 on: 19 / March / 2011, 06:55:31 »
Quote from: bashir on 19 / March / 2011, 03:58:09
I guess additional power also needed for the flip-flop and microphone?

Yes, and for the signal on the cameras usb connector to trigger it.
Use 4.8 or 6v batteries.
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Offline thepanoguy

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Re: trigger shot by sound detection?
« Reply #5 on: 19 / March / 2011, 12:10:25 »
To be successful using sound activation for photography you will need to use a VOX (voice operated relay) circuit.

http://circuitschematic.blogspot.com/2010/08/mini-operated-voice-relay-schematic.html

Kit:

http://www.electronickits.com/kit/complete/elec/k126.htm

The modified circuit is K126.pdf (half way down the page)

The original circuit was designed for hands free amateur radio microphone use and works on 12 volts DC. The audio circuit contains a limiting bandwidth filter to stop false triggering. If you use a normal audio amplifier circuit you will get false triggering. The relay which comes with the kit is 12 volts. The IC will operate down to 5 volts. I built the unit about a year ago and conducted extensive experiments with it. I removed the relay, used a short circuit limiting resistor and it works as advertised.

If you decide to build the circuit you would be better off using SDM than CHDK because SDM will trigger on the first pulse instead of the second.



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Offline Microfunguy

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Re: trigger shot by sound detection?
« Reply #6 on: 19 / March / 2011, 13:12:15 »


Any idea what the delay to actually taking the shot is ?


David
« Last Edit: 19 / March / 2011, 13:13:48 by Microfunguy »
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Offline thepanoguy

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Re: trigger shot by sound detection?
« Reply #7 on: 19 / March / 2011, 23:19:11 »
Reference K126.pdf

It is a while since I played with the device. Taking the shot was instant with an S3IS. ( I had no issues) I used the output at IC1 B Pin 7 then a current limiting resistor somewhere between 50 to 100 ohms. C2 determines the release time. From memory if C2 is removed from the circuit the delay time is instant.

It depends on your application. I used the circuit mainly to stop the ambient background noise false triggering the camera. The critical part of the circuit is all the components associated with IC1 A up to C3. You could use the first half of the circuit up to C3 and disregard the rest. I have seen similar circuits which feed the output of IC1 A pin 1 into a flip flop.

Addendum:

http://www.datasheetcatalog.com/datasheets_pdf/L/M/3/5/LM358.shtml

According to the National Semiconductor data sheet the LM358 is a high speed amplifier device. Theoretically the microphone circuit is just a bandwidth filter circuit and should not influence the operational speed of the IC. Therefore if your application is high speed triggering the above components associated with IC 1A should operate faster than any of the the CHDK / SDM compliant cameras.




« Last Edit: 20 / March / 2011, 00:14:06 by thepanoguy »
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