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Author Topic: Connecting Geophone Having 5 PIN Female Connector to Arduino Mega 2560  (Read 1585 times)
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Hi,

I've a Geophone (http://en.wikipedia.org/wiki/Geophone) which is having 5 PIN Female connector to observer output. Now I want to observe the output of Geophone by connecting it to Arduino Mega 2560. However I don't understand how I should do that as the Geophone has 5 pins (X,Y,Z , Earth and Common) and I don't have any knowledge of how to Interface it with an Arduino Mega 2560. I think such Geophone are called Triaxial Geophone.

Has anyone done that or any knowledge about same?
« Last Edit: January 26, 2012, 09:34:29 am by patilchetan » Logged

Mainz
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Hello,

which output type does your 5 pins have? A voltage signal from 0-5V?
If so, you can directly connect to a AD Channel of the arduino.

Regards
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Hi,

I don't have the datasheet of the sensor. I have borrowed it to understand
the output. Regarding output voltage range I can't comment. That is why I
wanted to know whether it will be advisable to directly connect it to ADC
of Arduino.

Also will Earth and common also go to ADC?

Thanks.
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nr Bundaberg, Australia
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X, Y and Z will be your axis so as long as they are < 5v you should be able to connect then to the analog inputs.

Earth and common, my guess is their common is what we normally call GND and their Earth is the chassis ground. In that case I'd connect common to the Arduino GND.

You may also find that the XYZ outputs do not vary their voltage much, in which case you won't have much resolution on the reading without amplifying.

I would test from common to X, Y and Z with a multi meter first.

______
Rob
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Rob Gray aka the GRAYnomad www.robgray.com

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Raw Geophone outputs are a AC voltage of very low frequency and low millivolt output voltages. So there are not a good candidate for direct attachment to a arduino analog input pin, as arduino needs DC only, no voltage with a negative component. Most applications using geophones use specific external pre-amp/filters/scaling electronics to Tailor the geophone to the application they are using it for.

So what is your usage or geophone and any specific technical specifications? Geophone can be very cool to play with, they are quite sensitive, although rather a physical large component for this day and age. Sometimes they can show up at bargain prices at surplus type outlets.

Lefty
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Hi,

The geophone shown here : http://www.instantel.com/pdf/720B0002.pdf
is the one I'm having. Now when I read the specification here, I don't understand why frequency range
is given instead of voltage for vibration monitoring. That holds me from connecting Arduino to Geophone.

@Graynomad : I did use multimeter however there was very low voltage shown. Also after looking into the above link I don't understand why frequency parameters are given for Vibration monitoring.

@retrolefty : What would you suggest?
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Quote
Raw Geophone outputs are a AC voltage of very low frequency and low millivolt
Well I wouldn't have picked that. You learn something new every day.

_____
Rob
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@Graynomad

When I vibrate Geophone with output connected to Multimeter then what I see is that both AC and DC voltages are produced.

So the voltage in both AC and DC are very low and it might be the case that I need some amplification.

However I don't see the logic in having both AC and DC Voltage.
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@ Graynomad

Quote
Well I wouldn't have picked that. You learn something new every day.

So no point of interfacing Geophone with Arduino?
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So no point of interfacing Geophone with Arduino?
That's up to you. It sounds like it's doable but not a simple hookup job so you have to decide if it's worth the effort or not.

It's getting a bit analog for me, sounds like retrolefty has more of an idea as to what is involved.

______
Rob
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A raw Geophone sensor is just a moving coil around a fixed magnet. It works on the same principle as a dynamic microphone 'sensor' or a permanent magnet loudspeaker. It is incapable of generating a DC output, just an AC voltage over a limited frequency band determined by the mechanical limitations of the design.

One must process this signal on a arduino just like the would and audio signal, with external circuitry scaled to fit in 0-5vdc range and a offset of +2.5 to center the response measurement around the zero crossings of the sensors signal. Often logarithmic amplifiers are required if one needs to try and capture the whole possible range that a geophone is capable of.

Geophones were designed to be used in arrays to detect the underground echos from explosive charges set off in exploring for oil, gas formations or other geological properties of the ground being explored.

 They are often used to form a lost cost seismometer and while not as sensitive and stable as a true seismometer there are much more compact and lower cost.

 I've looked into geophone circuits for hobbyist use in the past and there were many to be found on the web, just google around and I'm sure you can find enough information to get started. Make no mistake, the project will first have to focus on the external analog design needed to adapt a geophone to a arduino application.

Lefty
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@retrolefty :

Thanks for detailed explanation.

BTW : I again observed the output of my Geophone however this time on DSO. I was able gather following observation :
1) Max Output : 1 V
2) Min Output : 30 mV
3) Also high frequency noise

I'll make a pre-amplifier circuit and then an ADC and will give digital output to Arduino.
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