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How do I increase the sensitivity of my sound trigger?

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benbird

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Hi,
I have tried building a sound trigger referring to the instructions on the HiViz website.

I am having a couple of problems with sensitivity. When using a 100k resistor as they ask for it just didn't work so I started reducing the resistance and have found that a 470ohm works better for me, I can actually get a flash :) My current setup is as attached (couldn't work out how to get the pic to display)

My problem is, even though I can get a flash, its not very sensitive, I have to clap really hard to make it happen. Why does mine behave so differently to theirs, could it be the piezo being different? Also, by dropping the resistance, will my battery drain faster?

I am very new to electronics, this is the first thing I have ever built so any advice on how to make it work better would be much appreciated :)



Kindest regards,

Ben Bird
 

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  • Sound trigger.jpg
    Sound trigger.jpg
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Hi Ben

Two important details are the SCR Part # and what Piezoelectric device are you using. The problem is when websites post these small generic circuits they don't get very specific with part numbers for key parts. The SCR needs to have a very sensitive gate and the Piezoelectric device needs to be sensitive to sharp sounds. They don't fare well with a thump for example. The circuit could likely be improved using a tiny microphone and some amplification.

Ron
 
could it be the piezo being different
Yes it could, have you tryed anther one? can you post a link to the page you are building this from? and maybe a pic of your circuit? Andy
 
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Morning Andy

I believe he is working from here. They don't really get into the sensor or SCR details that I noticed.

Up and about early today huh? :)

Ron
 
Ron; Yes my son has a wrestling match this morning. So I must run but will take a look at the link latter. Good Morning to you. Andy
 
The original circuit has a 68,000 ohm base resistor to provide a low base current so the transistor is turned on only a little so a fairly weak sound level can turn it off.
Your modified circuit uses a 470 ohm base resistor value that is way too low and will cause the transistor to be turned on very hard which makes it almost impossible to turn off with the weak voltage from the microphone.
You said reducing the value of the base resistor made your circuit more sensitive so I think you have the collector and emitter pins of the transistor connected backwards. It works very poorly when its pins are connected backwards.
 
Thankyou so much Audioguru!! Problem solved! If you take a moment to have a look on the hiviz website, there are full, detailed instructions on how to put this thing together and it clearly shows the 2N2222A the same way round as the SCR's. I just turned it round, put my 68k resistor back in, and it works :)

I would put a link on, but the two posts I made earlier have gone in for moderation as im new.

Many thanks to all of you guys for your help :)

Ben Bird.
 
Dear Mr. Audio Guru

The attached circuit is taken from here. Your comments and thoughts on it would be most appreciated. The circuit does offer two means to trigger a flash but the audio is my interest.

This thread revived my interest in catching a bullet in flight. I need to do more homework, but nailing a bullet in flight has always had me curious.

Thanks
Ron
 

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  • Flash Trigger Sound.gif
    Flash Trigger Sound.gif
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Thankyou so much Audioguru!! Problem solved! If you take a moment to have a look on the hiviz website, there are full, detailed instructions on how to put this thing together and it clearly shows the 2N2222A the same way round as the SCR's. I just turned it round, put my 68k resistor back in, and it works :)

I would put a link on, but the two posts I made earlier have gone in for moderation as im new.

Many thanks to all of you guys for your help :)

Ben Bird.

Good to know Ben. I was posting as you posted. You can see my interest. :)

Ron
 
Ron; OK I have to ask. Seems like using a sound trigger would be slow and mite miss the bullet leaving the gun. Why not triger the gun and a high speed camra at the same time? Andy
 
Ron; OK I have to ask. Seems like using a sound trigger would be slow and mite miss the bullet leaving the gun. Why not triger the gun and a high speed camra at the same time? Andy

This is some of what I am unsure of. :)

The bang is the hot gasses exiting the muzzle. What I am more after is for example the projectile striking for example an apple or something maybe 10 feet downrange of the muzzle. I have seen some great images shot doing this. One trick is to open the shutter (remember this is done in the dark) and fire the gun. After the flash has fired then close the shutter. This is just something I have kicked around but have not really screwed around with.

Ron
 
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