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Topic: transducers and LONG distance wires (Read 5833 times) previous topic - next topic

julienb

hi there,

I'd like to know the constraints of long distance wires when we use transducers (I mean piezo).

I'd like to capture vibrations of some parts of a (small) building and I'd need LONG wires.
How can we handle this ?


all infos could be interesting,
julienb
http://www.julienbayle.net

Caltoa

What kind of transducers ? just a bare piezo element ? You can only use short wires with that. Perhaps a conditioned signal and coax.
What frequency range would you want ?

julienb


What kind of transducers ? just a bare piezo element ? You can only use short wires with that. Perhaps a conditioned signal and coax.
What frequency range would you want ?


low frequencies captation. I have to experiment, but I wouldn't have things greater than 200Hz, imho.
anyway, I would use something different than arduino. I'd need a bigger sampling rate.
julienb
http://www.julienbayle.net

Caltoa

What about the sensors ? brand ? type ? photo ?

CrossRoads

Either way, digitize it and send the data out using RS485 driver.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

julienb


Either way, digitize it and send the data out using RS485 driver.


I think I need an arduino per sensor, consider distances I'll have..
that way, I can read data with sensor/arduino, then send data with rj45 to the computer. ethernet cat7 is already set up there.
julienb
http://www.julienbayle.net

CrossRoads

Promini, simple & inexpensive at each location.
Can sample at 10x rate of 200Hz without issue.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Caltoa

CrossRoads is talking about the : Arduino Pro Mini.
http://arduino.cc/en/Main/ArduinoBoardProMini
They are small, but they don't have a USB connector, so you need a usb-to-serial converter. Once you have a setup for them, you can use them everything because they are so cheap.

The clones are very (very) cheap on Ebay :
http://www.ebay.com/sch/i.html?LH_BIN=1&_sop=15&_osacat=0&_from=R40&LH_PrefLoc=2&_nkw=arduino+pro+mini+-atmega128+-atmega168&_sacat=0

dave-in-nj

I have been trying to design a simple unit with the pro-mini from e-bay.  there are multiple chip layouts.  some of A6 and  A7 on the end next too A4 and A5, others have A4 and A5 nestled inside next to A3.....

also, because of the way A6 and A7, and A4 and A5 are laid out, you cannot use a common breadboard.

the price you pay for not paying a high price.

another option here might be the Teensy.   it has on-board ADC, 13bit usable. (16bit ADC)


julienb

Thanks a lot for all your feedbacks. couldn't answer before because of other projects on the go.

So now, I'm just trying to know about: piezo + arduino vs accelerometer + arduino

piezo seems easier/cheaper.
julienb
http://www.julienbayle.net

CrossRoads

A6/A7 are analog input Only, cannot be used for digital outputs.
Piezo' are definitely cheaper than accelerometer chips.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

julienb

Thanks CrossRoads.
How can I estimate frequency range I can capture with this or that piezo?
I mean, is there a specific feature to check ?
julienb
http://www.julienbayle.net

CrossRoads

Piezo's are spec'ed to have a resonant frequency
http://www.digikey.com/product-search/en/audio-products/buzzer-elements-piezo-benders/721679?k=piezo%20element&stock=1

See this data sheet as an example
http://www.cui.com/product/resource/ceb-27d44.pdf
It explains how the resonant frequency is determined.

Is there a specific range you are looking to capture?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

julienb

ok got it.
if I understand correctly, each piezo have a global range and there is an optimum which is announced as the resonant peak.

I need to experiment.
Working on building vibrations...
I think very low frequencies...
From several Hz to 100 I guess.
julienb
http://www.julienbayle.net

julienb

afaik, vibrations in buildings in a city with not a lot of metro going underground are from 0 to 10Hz ... no more.
I'm going to ask more specific questions in another thread. I just found this too: https://www.sparkfun.com/products/11744 expensive but it makes me thinking about these frequencies range I need to test..
julienb
http://www.julienbayle.net

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