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  1. #121
    Registered popspipes's Avatar
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    Default Re: Renishaw Probe

    I have too much free time on my hands again, I was wondering if someone has an input circuit from the probe to the machine to reduce the sensing current required? The measured current on mine is approximately 5 ma.
    I dont use the interface, and I am thinking that if I could get the sensing current lower it would be a good thing?? I think KStrauss had a circuit for it to reduce it to about .05 ma but I havent located the post for it and I dont think I saw the schematic either. If anyone has something similar I would be very interested.

    thanks for any input

    mike sr


  2. #122
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    Default Re: Renishaw Probe

    For now I simply feed the contacts power via a resistor and monitor the voltage across the contacts using an analogue input on an Arduino clone. I'd have to take my probe apart to determine the resistor's value but ISR that it is perhaps 100K.

    The attached patent shows in figure 3 what Renishaw does.

    Attached Thumbnails Attached Thumbnails Renishaw Probe-ep0501680a1_contactresistancestabilized-pdf  


  3. #123
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    Default Re: Renishaw Probe

    Thank you sir, I didnt think about a resistor in series, that would work as well and be much simpler.
    It works fine as it is but I could experiment with the resistor value and drop the current more as you stated.....

    tnx

    mike sr


  4. #124
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    Default Re: Renishaw Probe

    Originally Posted by brianbonedoc
    My boot was pretty much in tatters when I received my probe - so I just removed it all. Doesn't affect the probe as far as I can tell.

    Pops - as far as backlash - you know PathPilot can do that automatically. Just go edit the tormach_1100-3.ini file in the tormach_mill directory.

    Just add the BACKLASH line like I have below with your actual backlash. Do for ea axis. Axis 0 = X, Axis 1=y, and 2 = Z

    ---------------
    [AXIS_0]
    TYPE = LINEAR
    HOME = 0.000

    # Default=110 in/min 1.833/30.0 - just upped to 5/22
    MAX_VELOCITY = 5
    MAX_ACCELERATION = 22

    # 20 % higher max-vel and 50% higher maxaccel for backlash comp 7.2/26
    STEPGEN_MAX_VEL = 6
    STEPGEN_MAXACCEL = 26

    BACKLASH = 0.0008



    The backlash figures can be entered into PP 2.02, set it up this evening, They do have to be entered into the same area in the .ini file though, I had it entered a few lines above and it wouldnt work.

    Getting to the desktop does take a bit of doing though...........


    - - - Updated - - -

    Originally Posted by brianbonedoc
    My boot was pretty much in tatters when I received my probe - so I just removed it all. Doesn't affect the probe as far as I can tell.

    Pops - as far as backlash - you know PathPilot can do that automatically. Just go edit the tormach_1100-3.ini file in the tormach_mill directory.

    Just add the BACKLASH line like I have below with your actual backlash. Do for ea axis. Axis 0 = X, Axis 1=y, and 2 = Z

    ---------------
    [AXIS_0]
    TYPE = LINEAR
    HOME = 0.000

    # Default=110 in/min 1.833/30.0 - just upped to 5/22
    MAX_VELOCITY = 5
    MAX_ACCELERATION = 22

    # 20 % higher max-vel and 50% higher maxaccel for backlash comp 7.2/26
    STEPGEN_MAX_VEL = 6
    STEPGEN_MAXACCEL = 26

    BACKLASH = 0.0008



    The backlash figures can be entered into PP 2.02, set it up this evening, They do have to be entered into the same area in the .ini file though, I had it entered a few lines above and it wouldnt work.

    Getting to the desktop does take a bit of doing though...........


    mike sr


  5. #125
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    Default Re: Renishaw Probe

    Renishaw has many different probes and multiple methods of sensing any physical contact with their probes. Which probe do you have?

    Also be aware that the Renishaw probes that use mechanical switch contacts internally do far more that what that specific patent states; that is only one of *many* Renishaw patents. My Renishaw probes actually detect minute resistance changes in the contacts and totally remove the contact current before the contacts fully open, preventing any arcing. In addition to that there is an oil gel on the contacts to prevent oxidation.

    There are many ways to reduce the current down to at least nanoamp or even lower levels. Knowing which probe you have could assist with a simple design, powered by the DIN jack on the Tormach electrical cabinet (it obviously does not require using a microcontroller).



  6. #126
    Registered kstrauss's Avatar
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    Default Re: Renishaw Probe

    I suspect that most (all?) of us have a Renishaw MP3 as the basic "guts"; the MP7 that I purchased uses a slight variation of the MP3 together with additional electronics.

    Obviously a microcontroller is not required since none of the older Renishaw units include a microcontroller. However, a microcontroller is often a less expensive/ simpler/ cheaper/ better way to provide the desired functionality. As an example, my homebrew IR attached MP3 uses a micro in the probe to measure contact resistance and to generate the IR pulses. Another micro connected to the DIN receptacle decodes the IR pulses, handles signal loss, provides a visual indication of probe status and IR signal strength on a tiny OLED display, etc.

    In any case I am interested in your design.



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