Something completely different.

[tonyfoale]

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.

Click for full size
Here are the ingredients. It could not get much simpler.


In the making.


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.


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".


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.

[DIYer]

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:

Linear Velocity Transducer by tonyfoale

tags: dyno, measurement

[tonyfoale]

Thanks tonyfoale! We've added your Linear Vertical Transducer

Linear VELOCITY Transducer.

[Jon]

Thanks, all fixed.

[mwmkravchenko]

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.

[tonyfoale]

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.

[mwmkravchenko]

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.

[tonyfoale]

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.

[mwmkravchenko]

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.

[Jon]

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:

Horizontal Milling Machine by tonyfoale

tags: mill

Drum Brake Grinder by tonyfoale

tags: grinder, brake drums

Shock Absorber Dynamometer by tonyfoale

tags: suspension, measurement

Valve Holding Collet by tonyfoale

tags: valve, holder, collet

Laser Aligner by tonyfoale

tags: alignment, laser

Double Edge Fly Cutter by tonyfoale

tags: flange, fly cutter

Vertical Bandsaw by tonyfoale

tags: bandsaw

Surface Grinder by tonyfoale

tags: grinder, surface

Radius Gauge by tonyfoale

tags: gauge, radius

Motorcycle Frame Fabrication by tonyfoale

tags: motorcycle, frame

Treadmill Motor Modifications by tonyfoale

tags: safety, modification, motor

Cross Slide Screw Conversion by tonyfoale

tags: lathe, modification

Linear Velocity Transducer by tonyfoale

tags: dyno, measurement