# Help on sound activated props



## Erebus (Jul 28, 2009)

I have a few sound activated props (store bought) but there has to be a LOUD sound to make them go off. A few I have to walk around and hit to get them activated. Is there a way to make them more sensitive or change them to motion activated? If I can;t find any thing, I am thinking about putting vibrators on the bottom of them and have those go off on motion detectors.


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## Otaku (Dec 3, 2004)

What kind of motion do you want to detect? Light/dark (CdS diode) or warm body (PIR)? Either can be wired to a relay that will close the connection that is currently being handled by the sound detector.


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## fritz42_male (May 5, 2009)

Otaku would these be piezo activated?

If so then the circuit is just looking for a bit of voltage on the input lines. A common ground and a 3V signal might do it.

Maybe play with shorting one side of the piezo connection to the battery plus terminal - if the prop activates then easy to build a better trigger.


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## hpropman (Jul 27, 2008)

my web site has motion trigger information. Once you determine how the prop currently goes off then we can help you build a better controller for it.


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## Erebus (Jul 28, 2009)

I looked at it last night, and all I could see were 2 wires coming off a circuit board to a very small speakler like thing. I am guessing that is the mic. Does that help?


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## Otaku (Dec 3, 2004)

NTX JK said:


> I looked at it last night, and all I could see were 2 wires coming off a circuit board to a very small speakler like thing. I am guessing that is the mic. Does that help?


Yes, that's the mic, either a piezo or electret. When it hears a sound it closes a switch in the prop to activate it. I'm not sure if simply momentarily shorting those two wires together via a relay, mat switch or other method will result in triggering the prop, though. Anyone else got an idea about that?


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## fritz42_male (May 5, 2009)

Is the 'speaker thingy' a flat white disc with a metallic circle in the middle or a black plastic thingy? If it iz then it is a piezo mic. These generate a voltage when activated by sound or vibration.

If this is the case, shorting the 2 wires together won't work. Try shorting a link between the battery + terminal and each of the piezo wires - if the prop activates then this is where to connect the mat or whatever.


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## Erebus (Jul 28, 2009)

I believe it is white with a metallix circle. I am more than positive, but I will double check. Also, this runs off a dc power supply and not batteries, would I still just short the link and see if it turns on, or should I get a battery and just touch the wires to both ends?


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