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strain gauges — Parallax Forums

strain gauges

ArchiverArchiver Posts: 46,084
edited 2003-05-25 08:38 in General Discussion
Hi. I'm a mechanical engineer that just recently completed a
mechatronics graduate class that employed the basic stamp. I loved
the class and want to continue using the basic stamp for work related
problems. As such, I was wondering if anybody out there has
interfaced strain gauges to the basic stamp and if so, could you
please tell me what you used. I would love to configure my basic stamp
to collect strain date for me.

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-05-24 01:23
    In a message dated 5/23/2003 8:28:47 AM Pacific Daylight Time,
    jbechtel@e... writes:

    > Hi. I'm a mechanical engineer that just recently completed a
    > mechatronics graduate class that employed the basic stamp. I loved
    > the class and want to continue using the basic stamp for work related
    > problems. As such, I was wondering if anybody out there has
    > interfaced strain gauges to the basic stamp and if so, could you
    > please tell me what you used. I would love to configure my basic stamp
    > to collect strain date for me.
    >

    You will likly want to normalize the strain gage output for a 0 to 5 or 0 to
    10 volt range. The strain gauge output will go into an analogue to digital
    converter. The A/D data can then be easily be read and used by the stamp.


    [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-05-25 07:43
    You'll probably have to do some amplification of the strain gage
    signal before you can put it directly into an A/D converter. On the
    strain gages I have dealt with (for determining load on steel rolling
    mills), the gage outputs a few millivolts per volt excitation
    proportional to the amount of strain (rated in microinches per square
    inch I believe). So the max we get out of these things, with 5V
    excitation, is not even 100mV. We have a card in the PLC rack
    specifically for this type of signal so we can deal with it easily,
    but if you wish to put that value into the stamp you'll need to
    amplify it some before sending it into an A/D converter.

    Basically inside the strain gage there is a circuit called a
    Wheatstone bridge, which can sense a very small change in
    resistance. One of the elements in the bridge is the strain gage
    which varies in resistance as strain varies. Check out this link for
    some basic theory and simple circuits:

    http://www.omega.com/literature/transactions/volume3/strain2.html

    Also, if you put 'strain gage circuit' in on a Google search you will
    get a bunch of hits with some sites that may be able to help you out
    with some circuitry.

    --- In basicstamps@yahoogroups.com, smartdim@a... wrote:
    > In a message dated 5/23/2003 8:28:47 AM Pacific Daylight Time,
    > jbechtel@e... writes:
    >
    > > Hi. I'm a mechanical engineer that just recently completed a
    > > mechatronics graduate class that employed the basic stamp. I
    loved
    > > the class and want to continue using the basic stamp for work
    related
    > > problems. As such, I was wondering if anybody out there has
    > > interfaced strain gauges to the basic stamp and if so, could you
    > > please tell me what you used. I would love to configure my basic
    stamp
    > > to collect strain date for me.
    > >
    >
    > You will likly want to normalize the strain gage output for a 0 to
    5 or 0 to
    > 10 volt range. The strain gauge output will go into an analogue to
    digital
    > converter. The A/D data can then be easily be read and used by the
    stamp.
    >
    >
    > [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-05-25 08:38
    There are chips specifically designed to interface directly to bridge
    outputs of strain gage based load cell.
    I use AD7730 for weigh scale applications.

    look at this link for load cell fundamental:

    http://www.measurespec.com/tips/principles.htm


    >From: "Hernck" <jbechtel@e...>
    >Reply-To: basicstamps@yahoogroups.com
    >To: basicstamps@yahoogroups.com
    >Subject: [noparse][[/noparse]basicstamps] strain gauges
    >Date: Fri, 23 May 2003 15:22:31 -0000
    >
    >Hi. I'm a mechanical engineer that just recently completed a
    >mechatronics graduate class that employed the basic stamp. I loved
    >the class and want to continue using the basic stamp for work related
    >problems. As such, I was wondering if anybody out there has
    >interfaced strain gauges to the basic stamp and if so, could you
    >please tell me what you used. I would love to configure my basic stamp
    >to collect strain date for me.
    >
    >
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