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Thread: Something completely different.

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    Supporting Member tonyfoale's Avatar
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    Something completely different.

    How I made an LVT for my shock dyno.
    That is a Linear Velocity Transducer. As motion is involved I have made a movie.
    An LVT measures linear velocity over a limited range depending on the construction details. I wanted a transducer that had a range of 100 mm. with a maximum velocity of 1 m/s.

    Something completely different.-bits-4-100mm-lvt.jpg Click for full size
    Here are the ingredients. It could not get much simpler.

    Something completely different.-coil-all.jpg
    In the making.

    Name:  LVTcoils.JPG
Views: 3041
Size:  7.2 KB Something completely different.-mounted-2.jpg
    What is inside and mounted.

    Until I made this device I got the velocity information in the usual way of measuring displacement with a potentiometer and differentiating that signal. The process of numerical differentiation leads to noise in the velocity signal. The noise level depends on the resolution of the DAC (Digital Analog Conversion). I used a 12 bit LabJack U3 to convert the data, if I had used a 10 bit Arduino the noise level would have been 4 times more.
    This pic shows the difference between getting the velocity direct from the LVT and indirectly from the potentiometer.
    Something completely different.-velocity.jpg

    I still want displacement information, but I now get that by integrating the velocity signal which reduces noise. I get a slightly better displacement signal from the velocity than directly. This is often termed a "win-win".
    Something completely different.-displacement.jpg

    The movie is in two parts, the first shows the making and the results. As of writing this the second part is not ready but will describe the simple electronic bits and discuss resolution and range considerations. I'll add the link when ready.


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    baja (02-27-2021), Christophe Mineau (02-24-2021), DIYer (02-23-2021), FEM2008 (02-24-2021), JDrouin (02-23-2021), johncg (02-24-2021), Jon (02-26-2021), mwmkravchenko (02-23-2021), olderdan (02-23-2021), Saltfever (02-24-2021), yvonf (02-24-2021)

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    Thanks tonyfoale! We've added your Linear Velocity Transducer to our Motorcycle category,
    as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:


    Last edited by Jon; 02-23-2021 at 02:05 PM.

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    Supporting Member tonyfoale's Avatar
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    Quote Originally Posted by DIYer View Post
    Thanks tonyfoale! We've added your Linear Vertical Transducer
    Linear VELOCITY Transducer.

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    Jon (02-23-2021)

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    Thanks, all fixed.

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    Very interesting Tony!

    The only thing I can wonder about is your using an aluminium tube to house your magnets. Did you want to use only the ends of the magnets? Because aluminium and magnetic flux repel one another. The ends of your composite magnet will see the greatest flux concentration. It may be the method behind your madness. Because you have done quite a lot of research in the rest of this design.

    Among other things I design loudspeakers for a living. Working as a consultant for a number of different companies. I do a lot of design work with various types of magnets for designing woofers, and tweeters of various sizes and shapes.

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    Supporting Member tonyfoale's Avatar
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    Quote Originally Posted by mwmkravchenko View Post
    Very interesting Tony!

    The only thing I can wonder about is your using an aluminium tube to house your magnets. Did you want to use only the ends of the magnets? Because aluminium and magnetic flux repel one another. The ends of your composite magnet will see the greatest flux concentration. It may be the method behind your madness. Because you have done quite a lot of research in the rest of this design.
    Aluminium is paramagnetic and relative movement of aluminium and a magnetic field will generate a repulsive force as you say but in this case there is no RELATIVE movement. The magnet and aluminium tube move together, I pointed this out in the video when talking about eddy currents.
    Yes the ends of the magnet see the greatest flux concentration, that is what is required and I demonstrated that with my little screw driver test. If there were areas of concentration along its length a lack of linearity would ensue in the output signal, it would be position and velocity sensitive. I only want velocity sensitive.
    There is no method in my madness, it just comes naturally.

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    Quote Originally Posted by tonyfoale View Post
    Aluminium is paramagnetic and relative movement of aluminium and a magnetic field will generate a repulsive force as you say but in this case there is no RELATIVE movement. The magnet and aluminium tube move together, I pointed this out in the video when talking about eddy currents.
    Yes the ends of the magnet see the greatest flux concentration, that is what is required and I demonstrated that with my little screw driver test. If there were areas of concentration along its length a lack of linearity would ensue in the output signal, it would be position and velocity sensitive. I only want velocity sensitive.
    There is no method in my madness, it just comes naturally.
    This very same method of using a paramagnetic metal be it aluminium or better yet copper is used in a proper loudspeaker motor to control inductance rise in a voice coil. You know this I am sure. The voice coil is an analog to your single layer solenoid winding.

    You could not have done a better job of an easy to make composite magnet with very focused end high flux density if you tried.

    What I failed to type the first time is I am impressed with your engineering research and competency. A pleasure to watch your videos and learn from them.

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    Quote Originally Posted by mwmkravchenko View Post
    What I failed to type the first time is I am impressed with your engineering research and competency. A pleasure to watch your videos and learn from them.
    I appreciate your kind words but they make me feel like a fraud. I do very research on anything.

    Here is the link to the second part of the video, I hope that you like it as much.


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    Quote Originally Posted by tonyfoale View Post
    I appreciate your kind words but they make me feel like a fraud. I do very research on anything.

    Here is the link to the second part of the video, I hope that you like it as much.

    Watched. And the little research at present comes from a lot of research in the past. I'm not as old as you are Tony. But I don't have to look up everything that I put my hands to either. Some things we don't loose with time. Other areas of interest require a refreshing of what we once knew well.

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    Congratulations tonyfoale - your Linear Velocity Transducer is the Homemade Tool of the Week!

    This unique build, which further develops your previous winning Shock Absorber Dynamometer, will be useful to people doing CNC machine building.

    Some more nice builds from this week:

    Mill Scale Removal Methods by Haslip Cycle Works
    Mill Angle Plate by bouboulas
    Welding Table by fox craft
    Metalworking Table by Tuomas
    Vise by orioncons36
    Lathe Chuck Spacers by editor@glue-it.com
    Disc Punch by editor@glue-it.com
    Quorn Tool and Cutter Grinder Spindle Housing by ttmrj
    Circle Cutting Jig by Workshopshed
    Glass Cutter by Mr.DK DIY
    Clothespins by Philip Davies
    Knee Mill Head Lifter by LMMasterMariner
    Drill Press Sanding Drum by HandmadeCreativeChannel
    Downdraft Sanding Table by Didpoolhall
    Floating Tap Holder by machining 4 all
    Double Duty GPIO Pins by rgsparber
    Rip Cut Jig by Didpoolhall


    tonyfoale - we've added your tool entry to our All Homemade Tool of the Week winners post. And, you'll be receiving a $25 online gift card, in your choice of Amazon, PayPal, or bitcoin. Please PM me your current email address and gift card choice and I'll get it sent over right away.


    This is your 13th Homemade Tool of the Week win! Here are all of your winning tools:


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