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  • Arduino OLED Tacho BR2J

    My problem is mounting something to read true spindle speed not only in high but also in backgear so I am making an optical Arduino Tacho for my Bridgeport BR2J following this excellent Instructable the main advantage with the Arduino is that you can modify the sketch so that it will count gear teeth rather than fixed single revolutions this should open up more "read head" mounting opportunities.

    I was thinking of mounting it somehow so it reads the backgear teeth, anyone out there have any experience of doing this on a BR2J?

    Test version seems to be accurate when compared with my far eastern hand held device.

    The OLED display is currently only 0.96" but I am now looking at using a bigger OLED or TFT display, if I can find something at a price I like!









    Paul

  • #2
    I gave thought to reading rpm off the spindle business end but it moves up and down. I had my magnet and sensor mounted to the top bearing cap but it spins at pulley speed so it didn't read correctly in low gear. While I had the top apart for exploratory surgery (another topic), I mounted the sensor in the bull gear cover plate and put a magnet "in" the bull gear. Since the bull gear turns the spindle, I always get the spindle rpm no mater what pulley, gear or frequency of motor.







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    • #3
      Originally posted by _Paul_ View Post
      My problem is mounting something to read true spindle speed not only in high but also in backgear so I am making an optical Arduino Tacho for my Bridgeport BR2J following this excellent Instructable the main advantage with the Arduino is that you can modify the sketch so that it will count gear teeth rather than fixed single revolutions this should open up more "read head" mounting opportunities.

      I was thinking of mounting it somehow so it reads the backgear teeth, anyone out there have any experience of doing this on a BR2J?

      Test version seems to be accurate when compared with my far eastern hand held device.

      The OLED display is currently only 0.96" but I am now looking at using a bigger OLED or TFT display, if I can find something at a price I like!


      Paul
      Nice, I REALLY like the display. Very cool.

      If you are not stuck on an optical pickup, these parts are specifically designed to read gear teeth for speed sensing. Six bucks in onesey-twosey quantities. I've used similar parts in the past, easy to use and effective if you have a handy gear to use for the sensed element. I think the gear needs to be a magnetic metal, but having lots of teeth to count gives you good low speed resolution and response.

      Very cool project.

      Comment


      • #4
        That is a very good idea to measure your spindle RPM. I would love to be able to do that.

        I am in a very slow process of connecting VFD to my Bridgeport clone mill. It runs, but does not have any remote controls yet. It is a variable speed head, so I checked the actual spindle speeds with a hand held optical tach vs what dial shows you. At the low range dial set at 60 RPM produces 84 RPM actual speed, 470 RPM setting produces 585 actual RPM. At high range 1000 RPM setting is equal to 1295 spindle speed. You get the idea...

        I think this big mistake mostly came from China being a metric contry and having a 50Hz power supply. My VFD was set to 60 Hz output. You start vary the VFD frequency and it is easy to get lost. That's why I am thinking about a tachometer idea. My biggest problem is what part of the mill I am going to read with a sensor. On the picture above CCWKen shows the sensor reading the magnet in a bull gear. But once you put the head in a low range (backgear), the bull gear goes down and sensor no longer can read it. What am I missing?

        You could read the gear teeth with a proper sensor, but bull gear moves too much up and down. Maybe sensor can still read it? Does anybody have a working tachometer on a vertical mill? How did you do that?

        Comment


        • #5
          Originally posted by mikey553 View Post
          It is a variable speed head, so I checked the actual spindle speeds with a hand held optical tach vs what dial shows you. At the low range dial set at 60 RPM produces 84 RPM actual speed, 470 RPM setting produces 585 actual RPM. At high range 1000 RPM setting is equal to 1295 spindle speed. You get the idea...

          My biggest problem is what part of the mill I am going to read with a sensor. On the picture above CCWKen shows the sensor reading the magnet in a bull gear. But once you put the head in a low range (backgear), the bull gear goes down and sensor no longer can read it. What am I missing?

          You could read the gear teeth with a proper sensor, but bull gear moves too much up and down. Maybe sensor can still read it? Does anybody have a working tachometer on a vertical mill? How did you do that?
          That is the problem with the BR2J Bridgeport is actually finding something to get a reading from, CCWKen's machine is a step belt head so the bullgear is in a fixed position but as you have noted there is no such luxury on the Varispeed BP.

          Paul

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          • #6
            I never got around it it but I was going to simply read the splines (and divide by the number of splines) on the spindle just above where the power feed gear take-off is. Means getting "inside",, but..

            On my mill I set my vfd to display rpm (scaled frequency) with the varispeed set to 4200rpm. I can mentally halve it when I occasionally wind down to 2100, or divide by 4 at 1050. I could also reprogram the constant divider, but can't be bothered.

            For step pulley, another way is to read the VFD 0-10v dc (proportional to frequency) via a $5 4 digit panel voltmeter. Add a 4 position switch with resistors to scale the input voltage based on the belt position used. I used the same idea on my belt sander, and switched between rpm and SFM
            Last edited by lakeside53; 04-18-2018, 10:47 AM.

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            • #7
              But once you put the head in a low range (backgear), the bull gear goes down and sensor no longer can read it. What am I missing?
              The bull gear doesn't move up and down--The drive pulley assembly moves up and down to disengage/engage the dog drive in the center. There's a separate lever on the head that moves the back gear up and down to drive the bull gear. The back gear is shown disengaged in the first picture (behind the bull gear). This is, of course, on the belt drive head. The bull gear remains on a single plain.

              Comment


              • #8
                For those wanting to read the bull-gear teeth, watch out for the max frequency. I my case I had to scratch that - 6000 (I can do more) rpm x tooth count was too high for available sensors a few years back. That's why I decided it was more practical to read the splines.

                Comment


                • #9
                  Originally posted by lakeside53 View Post
                  For those wanting to read the bull-gear teeth, watch out for the max frequency. I my case I had to scratch that - 6000 (I can do more) rpm x tooth count was too high for available sensors a few years back. That's why I decided it was more practical to read the splines.
                  Now that's something I had definitely not considered, makes reading the splines seem the sensible option.

                  There should be enough space to mount the photodiode and LED in the cavity where the downfeed power take off is, my problem then is how to protect them from oil contamination as my spindle has open bearings relying on lube from the drip feed oiler.

                  Paul

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                  • #10
                    Originally posted by lakeside53 View Post

                    For step pulley, another way is to read the VFD 0-10v dc (proportional to frequency) via a $5 4 digit panel voltmeter. Add a 4 position switch with resistors to scale the input voltage based on the belt position used. I used the same idea on my belt sander, and switched between rpm and SFM
                    That's really neat and simple to implement trick.

                    Comment


                    • #11
                      Originally posted by _Paul_ View Post
                      Now that's something I had definitely not considered, makes reading the splines seem the sensible option.

                      There should be enough space to mount the photodiode and LED in the cavity where the downfeed power take off is, my problem then is how to protect them from oil contamination as my spindle has open bearings relying on lube from the drip feed oiler.

                      Paul
                      Not a photo-diode... you can get a sealed sensor that gives a signal when it detects the "tooth" of the spline passing.

                      Comment


                      • #12
                        Quote Originally Posted by lakeside53 View Post

                        For step pulley, another way is to read the VFD 0-10v dc (proportional to frequency) via a $5 4 digit panel voltmeter. Add a 4 position switch with resistors to scale the input voltage based on the belt position used. I used the same idea on my belt sander, and switched between rpm and SFM
                        That's really neat and simple to implement trick.
                        Originally posted by MattiJ View Post
                        That's really neat and simple to implement trick.
                        Yes, it is, but there is another way depending on your VFD

                        My Mitsubishi Freqrol A-200 has two readouts , They can be whatever you want . On mine, the actual frequency is on one readout and for the other , I have the actual RPM by using a calculated factor like 1115/60= 18.2 (or whatever) for the second step on the step head (which is 1115 RPM at 1740 on the motor or 60 CPS.

                        Rich

                        if you want, just learn the parameter # and call it up if you switch steps and enter in the new factor.
                        Last edited by Rich Carlstedt; 04-18-2018, 06:15 PM.

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                        • #13
                          That's what I do on my varispeed mill - factored frequency for RPM. Using a panel meter and a switch allows you to "select" which belt position and have an rpm readout relatively accurate for each.

                          Of course... if you never change the belt position you can just do the one division and display 'rpm' on the VFD (assuming has that feature)
                          Last edited by lakeside53; 04-18-2018, 08:07 PM.

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                          • #14
                            Originally posted by lakeside53 View Post
                            Not a photo-diode... you can get a sealed sensor that gives a signal when it detects the "tooth" of the spline passing.
                            Sounds good, is there a specific type I should look for?

                            Paul

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                            • #15
                              Allegro has a gear tooth sensor:

                              https://www.allegromicro.com/en/Prod...Cs/ATS667.aspx

                              You can get them on eBay for about USD $7.

                              bob

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