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R Photographic Trgger Unit

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2007-2009 » Archive through 10 June, 2009 » R Photographic Trgger Unit « Previous Next »

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tenala
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Username: tenala

Post Number: 17
Registered: 05-2009

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Posted on Thursday, 04 June, 2009 - 08:24 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Apologies for the delay but thank you Zeit for your advice on this circuit, have modified the circuit by increasing the 470K pre-set to 1M pre-set and improvement is really noticeable.
Now, can anyone sugest a suitable mod or new circuit to give a trgger by vibration?

I wait in antisipation
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ant
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Username: ant

Post Number: 425
Registered: 05-2006

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Posted on Thursday, 04 June, 2009 - 11:12 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hello Tenala,

I vaguely recall a circuit using a large diameter piezo transducer as a microphone for very low frequency sounds/vibrations. There are also vibration sensors which are very commonly used in the intruder alarm industry, mechanical and I'm sure by now electronic too.

Regards Ant
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tenala
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Username: tenala

Post Number: 18
Registered: 05-2009

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Posted on Friday, 05 June, 2009 - 06:41 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Thank you Ant, piezo transducer sounds (pardon the pun) what I need but I've yet to come across one all I've seen so far is the mechanical type with some being no more than a basic tilt switch. Any idea where I could obtain a piezo transducer?

Regards Tenala
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ant
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Username: ant

Post Number: 427
Registered: 05-2006

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Posted on Friday, 05 June, 2009 - 07:43 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hello Tenala,

Offhand I don't remember the details, they found a fairly large one. There're these:

http://www.maplin.co.uk/Module.aspx?ModuleNo=3202
http://www.rapidonline.com/Electrical-Power/PA-Audio-Video/Sirens-Sounders-Transducers/Uncased-piezo-transducer/35847/kw/piezo

Wasn't there a drum machine recently which used this sort of thing?

Regards Ant
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ecotec
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Username: ecotec

Post Number: 12
Registered: 09-2007

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Posted on Saturday, 06 June, 2009 - 10:55 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi Tenala,

Here is a link for a vibration sensor :-

http://www.parallax.com/dl/docs/prod/compshop/PiezoInfo.pdf

Regards Ecotec
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green
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Username: green

Post Number: 45
Registered: 03-2009


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Posted on Saturday, 06 June, 2009 - 01:33 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi Tenala,

If you have a piezoelectric sounder you can make your own. Spread a little adhesive or paint on the center of the diaphragm and sprinkle some rough sand on it. When it is dry place a ball bearing on the diaphragm and any movement will generate a voltage, as the ball moves on the rough surface.

It is also possible to make s precision sensor to indicate when a vibration is at 1 g. Leave out the paint and just sit the ball bearing on the diaphragm. With slow velocity vibrations the ball will sit on the diaphragm and follow the movement, but as the velocity increases, at exactly 1g the ball will start to chatter (bounce). Don't forget you may get several hundred volts from this kind of sensor. Have fun .....

green.
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tenala
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Username: tenala

Post Number: 19
Registered: 05-2009

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Posted on Saturday, 06 June, 2009 - 09:03 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Thanks guys I'll check out your recommended sites. However Mr. Green I think I'll just stick to my Kntting (photography that is)but your input will be placed on record.

Regards to all
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boris
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Username: boris

Post Number: 405
Registered: 05-2005


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Posted on Sunday, 07 June, 2009 - 05:53 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I built a surprisingly effective seismometer using a basic piezo disk. It was suspended by it’s outer edges (in the same plane as the ground) at two opposing points by a small U-shaped wooden frame. Then I glued an old D-Cell battery (on it’s side) to the centre of the disk. This pre-stressed the disk and increased the sensitivity I think.

A 741 op-amp for gain and that’s the whole thing. It was amazingly sensitive. Using my CRO as the display, and the device on my desk, I could easily detect a matchstick dropped on the floor from a height of 1m, over 2m away. I clearly saw the effect of traffic, people moving around the house, a car with a bad driver ‘kangarooing’ outside (approx 20m – 30m from the sensor).

I spent a while trying to work out what was wrong with it because of a spurious constant 100Hz signal. I thought there was some sort of EM pickup. Turned out to be the mains transformer in my CRO vibrating slightly :-)

I’m a fan of peizo disks. Cheap and dead versatile.
Thank you for not breeding.
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atferrari
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Username: atferrari

Post Number: 709
Registered: 05-2005


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Posted on Monday, 08 June, 2009 - 11:36 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hola Boris,

and the device on my desk

Just to have a clear idea: was the disk hanging from the wooden frame, sitting on the desk or...?

Could you provide a simple drawing?

I would like to experiment with something simple as that.

Gracias
Agustín Tomás - Buenos Aires - Argentina

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