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Watt meter on my Mill

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  • Watt meter on my Mill

    I like to know how hard I am working my tools so I added a Wattmeter.

    First I tested at my desk:


    Then installed it on my mill, works great!!





    Huh, preview does not show the pictures, hope you see them if not I will add links.


    Ralph

  • #2
    Well the forum does not like my Google Drive image links!!

    Here are 4 images as links:

    1
    2
    3
    4

    Comment


    • #3
      Really the pictures of the meter and mounting are only passingly of interest. I came in here to see the HARD NUMBERS! ! ! !

      Like how much power is needed just to run the machine without cutting then how much additional does it draw during different cutting amounts during typical hogging and finishing cuts. And how different cutters alter the values if any. And how do these numbers change for running at different speeds. That'll be where the fork hits the meat! ! ! !

      I can see this running for a while as you run the trials and obtain the readings. It'll be extremely interesting.
      Chilliwack BC, Canada

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      • #4
        Some decent VFDs can display instantaneous power or current
        If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

        Comment


        • #5
          Your mill is probably going to be limited to rigidity not spindle HP. It might be interesting to look at the numbers but I'm not sure if it'll be much help in practice. My knee mill has a 1/2hp motor, replacing the old pancake motor BP originally fitted. Plenty for endmills, maybe a bit too little for a face mill.

          Sent from my XT1053 using Tapatalk

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          • #6
            Wow, $11.90 for a power meter. That tempts me to get one or more.

            I noticed that there is something that is probably a current sensor in the outlet box. Did that come with the meter or did you have to purchase it separately?

            And is it a true power meter that takes the power factor into account or is it just a VA meter?
            Paul A.
            SE Texas

            And if you look REAL close at an analog signal,
            You will find that it has discrete steps.

            Comment


            • #7
              Hi Ralphxyz
              You are on to it by fitting a meter to check the loading on the motor amps as this will allow you to get the optimum speed and feed rate without overloading the motor.
              Spent a chunk of my working life as a factory engineer with variety of motor driven machinery with amp meters fitted that by regular monitoring and recording helped with early intervention before a breakdown occurred.
              Now my lathe and mill have 15 0 15 amp meters on the DC motor leads.

              Eric

              Comment


              • #8
                Originally posted by Paul Alciatore View Post
                Wow, $11.90 for a power meter. That tempts me to get one or more.

                I noticed that there is something that is probably a current sensor in the outlet box. Did that come with the meter or did you have to purchase it separately?

                And is it a true power meter that takes the power factor into account or is it just a VA meter?
                It'll cost any of us $12 to find out...

                I see it shows the voltage and amperage and power along with watt-hrs. If one can read the voltage and amperage and APPARENT watts I wonder if they could use that as a way to calculate any phase shift and power factor? So so even if the meter doesn't provide the real watts then it would be possible to enter the readings into a spread sheet with the equations in the back ground to figure this out.
                Chilliwack BC, Canada

                Comment


                • #9
                  Originally posted by BCRider View Post
                  It'll cost any of us $12 to find out...

                  I see it shows the voltage and amperage and power along with watt-hrs. If one can read the voltage and amperage and APPARENT watts I wonder if they could use that as a way to calculate any phase shift and power factor? So so even if the meter doesn't provide the real watts then it would be possible to enter the readings into a spread sheet with the equations in the back ground to figure this out.
                  Look more carefully at the photos. This:

                  https://drive.google.com/file/d/0B3d...Q0alVNR1U/view

                  Is showing 122VAC, 2.69A, and 195.4 W. The apparent power is 122 x 2.69 = ~ 328 W. The actual power shown is 195.4. The readings equate to a power factor of 195.4 / 328 = ~0.59, call it 0.6. That is reasonable for a motor under a good load, and even more reasonable if any other items are powered, such as control box parts, perhaps a light, or contactor etc.

                  So, either the wattmeter is totally inaccurate, OR it is actually reading V x A x Cos (theta)
                  .
                  CNC machines only go through the motions.

                  Ideas expressed may be mine, or from anyone else in the universe.
                  Not responsible for clerical errors. Or those made by lay people either.
                  Number formats and units may be chosen at random depending on what day it is.
                  I reserve the right to use a number system with any integer base without prior notice.
                  Generalizations are understood to be "often" true, but not true in every case.

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                  • #10
                    I use this one (easier to connect and configure):
                    http://www.ebay.com/itm/LCD-Digital-...0AAOSwo4pYHr8g


                    Max 16A though

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                    • #11
                      Does about the same as a Kill-A-Watt meter except the KAW meter can also calculate electric costs and can be moved from plug to plug. Works pretty good. I used one to determine whether I could use a particular wireless remote to control some dust filter fans in the shop. It's also fun to check other equipment and house appliances.

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                      • #12
                        My VFD on my round column mill will read out like that but I have it programmed to read spindle speed most of the time. The mill is converted to 3 phase.
                        CPeter
                        Grantham, New Hampshire

                        Comment


                        • #13
                          It is perhaps even easier to read true watts than apparent watts (VARS) using inexpensive digital technology. It is just a matter of taking samples of the voltage and current waveform reasonably close to simultaneous. A typical PIC (or Arduino) can easily take a sample/hold reading in 50 uSec. At 60 Hz, 50 uSec corresponds to a phase shift of 1.08 degrees, which is close enough for a non-lab consumer device such as this. The product of the two readings is instantaneous power. 6000 samples per second can be averaged for a smooth reading at a comfortable update rate of 2-4 per second. The current and voltage readings can be processed to provide true-RMS response with no additional expensive hardware.

                          One limitation of this meter appears to be that it has a limited range of AC volts and frequency, so it may not be suitable for monitoring a wide range variable speed drive output. But it should be perfectly capable for most needs.
                          http://pauleschoen.com/pix/PM08_P76_P54.png
                          Paul , P S Technology, Inc. and MrTibbs
                          USA Maryland 21030

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                          • #14
                            I just read current on my vfd. With constant feed and DOC.. I can watch the tool wear increase the current. 50% increase... time to take a good look at the tooling.

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