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  • Tachometer Kits

    Any one out there know if tachometer kits are available from a supplier in Canada? Thanks


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    George L
    George L

  • #2
    Don;t know about Canada but have you checked out usdigital.com?
    I just need one more tool,just one!

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    • #3
      George

      You talking about your VFD? Does it have a tach input? I can program mine to display proper rpm based on the VFD output.

      You can build one yourself - just need an DAC and phototransistor input. Check your local Active components store - they may have kits for a tach, or you can buy cheap ones at Canadian tire and just roll your own.

      Comment


      • #4
        <font face="Verdana, Arial" size="2">Originally posted by Thrud:
        George

        You talking about your VFD? Does it have a tach input? I can program mine to display proper rpm based on the VFD output.

        You can build one yourself - just need an DAC and phototransistor input. Check your local Active components store - they may have kits for a tach, or you can buy cheap ones at Canadian tire and just roll your own.
        </font>
        Hi Thrud: I looked at the CTC and Princess Auto tachometers and I may end up with one of those. I really want a digital one though. Next chance I get to visit the local Radio Shack store I'll look there too. Thanks

        PS Yes the VFD is programmed to read rpm for the lathe but, since I will be running either the lathe or the mill I will need a tachometer for one of them or I shall have to re-enter the parameter each time I change machines.

        [This message has been edited by GJLawlor (edited 02-02-2003).]

        [This message has been edited by GJLawlor (edited 02-02-2003).]

        [This message has been edited by GJLawlor (edited 02-02-2003).]
        George L

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        • #5
          Don't know how many would want to go to this much trouble, but here's what I did to measure the rpm of my mill/drill spindle. Put a T-shaped piece like a lathe chuck wrench in the mill collet. Put a small magnet on one end of the T. Place a coil of fine magnet wire near the end of the T so the magnet passes it at each revolution. Attach the ends of the magnet wire to the mike input of the computer sound card. Use the sound recorder software under utilities/multimedia in the programs directory to record the resulting signal. Use the AudioView software to display the waveform and count how many peaks occur per second. For more accuracy, run the digitized wave data through a fast Fourier transform (Excel has one). I found all this software (except Excel) on my computer as it was delivered. The Sound Blaster audio card that came with the computer has an analog to digital (A/D) converter (at the end of the mic input) that handles up to 40 KhZ (and down to DC). The signal from the magnet/coil detector is not likely to overload the A/D, but start with the volume controls turned way down.

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          • #6
            Herb that is absolutely ingenious. What a marvelously inventive approach. I have all the stuff to do this with but I will still try for an inexpensive digital tachometer. Thanks

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            George L
            George L

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            • #7
              Please, why is a digital tach needed? How accuartely do you need to know RPM or what ever with a VFD?
              Steve

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              • #8
                <font face="Verdana, Arial" size="2">Originally posted by docsteve66:
                Please, why is a digital tach needed? How accuartely do you need to know RPM or what ever with a VFD?
                Steve
                </font>

                Good Question Steve. I wish to know the spindle RPM to be able to calculate the cutting rate in Feet Per Minute based on the size of the work piece or the cutting tool. Good CNC machines and software use RPM data accurate to 1 or 2 RPM to control feed and / or RPM to give good tool life and fast performance and a good finish.

                George
                George L

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                • #9
                  Glad my machines are obselete like me---all I gotta do is check the belt positions on the pulleys and I can quickly look at the chart and tell what rpm I'm turning.

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                  • #10
                    Hi, Just read the above and the timing was perfect. I just installed an older AB (Bulletin 1333) VFD on my lathe and am now thinking about adding some of the bells and whistles it came with. The manual says I can add a 0 to 1ma "frequency meter" to the drive to read speed. What is this meter and where might I find one? Are they talking about an analog meter like in a older voltage meter? Can the signal be used to drive a digital meter? Not being an old timer at this, I turn to the experiance on the board for help and I am never disapointed.
                    Tadd, from the sunset coast

                    Comment


                    • #11
                      Tadd, a 0 to 1 ma meter is just a device that reads current, in this case, l ma, or .001 ampere. It's being called a frequency meter in your case because your vfd has an output to the meter that corresponds frequency (rpm) to a level of current, 1 ma, at full needle deflection, where I assume is at maximum rpm. Any analog meter will work for this if it has a range where 1 ma can be read on one of it's scales. It doesn't matter if the scale is, say, 10 ma, just assume full rpm is read at the 1 ma mark on the scale. A digital meter may or may not give a proper reading because it doesn't necessarily interpret the input signal from the vfd properly. Get a cheap analog meter with a 1 or a 2 ma range, it will do the job fine.
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                      • #12
                        George

                        Once you get use to using it, you will not need the readout (unless curious). I adjust purely by cutting performance pushing the tools as far as I can without ruining the carbide.

                        Comment


                        • #13
                          Thanks, Thats kind of what I thought the manual was talking about. Get the meter out of a $10.00 Radio Shaft meter and use it for freq/speed meter. Your right Thrud, so often I install the bells and whistles and end up not using them because the "feel" method seems to work better.

                          [This message has been edited by Tadd (edited 02-04-2003).]
                          Tadd, from the sunset coast

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                          • #14
                            <font face="Verdana, Arial" size="2">Originally posted by Thrud:
                            George

                            Once you get use to using it, you will not need the readout (unless curious). I adjust purely by cutting performance pushing the tools as far as I can without ruining the carbide.
                            </font>
                            Thrud I don't have the touch that some of you guys who wave been machining for , shall we say extended periods of time, do. Ever watch a TIG artist at work laying down a beautiful almost flat bead that fills the weldment gap? I can TIG weld but it sure don't look like that. And you are quite right about feed rates that may be pushed to escessive limits. Some of the books say, and my experience confirms this, that the single biggest mistake beginners make is that they are too timid about feed rates and cutting speeds. Since I'v made some improvements to my Grizzly it seems that the finish of the cut is definitely better at higher speeds and feed rates. So with th Tachometer I guess I am trying to assist my lack of experiende and ability with better data.

                            George


                            George L

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                            • #15
                              <font face="Verdana, Arial" size="2">Originally posted by darryl:
                              Tadd, a 0 to 1 ma meter is just a device that reads current, in this case, l ma, or .001 ampere. It's being called a frequency meter in your case because your vfd has an output to the meter that corresponds frequency (rpm) to a level of current, 1 ma, at full needle deflection, where I assume is at maximum rpm. Any analog meter will work for this if it has a range where 1 ma can be read on one of it's scales. It doesn't matter if the scale is, say, 10 ma, just assume full rpm is read at the 1 ma mark on the scale. A digital meter may or may not give a proper reading because it doesn't necessarily interpret the input signal from the vfd properly. Get a cheap analog meter with a 1 or a 2 ma range, it will do the job fine.</font>

                              Darryl's right on the money. On the face of the meter there will be some fine printing saying something like 'x number of ohms per volt' or 'x number of volts per milliamp' or something that tells one what is required to give a full scale deflection on the meter. You want to know that so as to avoid overloadng the meter. Use a digital volt meter and check (between VFD ground and the output)what that special output on your VFD does as you vary the speed. If the readings look strange put a 10,000 ohm (10 k ohm) accross the output and ground and then put the meter across the resister. Of course if you have an oscilloscope use it. (boy I sure could use a spell checker here) Good luck, let us know how you make out.
                              George.
                              George L

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