Bowman Magnet Motor Open Sourcing Project

Status: Project commenced Dec. 2003 with claim to a working device, which later, after three months, ended up running down due to demagnetization.  No replications were accomplished though several were attempted.

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   Make for $6.00

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PES Network Inc > Open Sourcing Projects > Magnetic Motors > Bowman > Instructions > Build Gauss Meter to Test Magnets

Build Cheap Gauss Meter; Accurate Measurement Protocol

See: Hugh Campbell Offers to Purchase, Cut, Characterize Magnets at Cost

Gauss Meter for $6.00

From: Sterling D. Allan
To: PES Magnetic Motor (Bowman) egroup
Sent: Monday, December 29, 2003 6:01 AM
Subject: [PES_BMM] $6.00 Gauss Meter adequate?
I've put a link to the $6.00 make-it-yourself Gauss meter

from the Bowman Motor site.

The question we need to answer before the site goes public is whether or not this make-shift Gauss meter will be adequate for the task.

Which of you, if any, plan to make this $6.00 Gauss meter?


Saturates When Up Close

From: Eric Vogels
Sent: Monday, December 29, 2003 12:14 AM
Subject: Re: [PES_BMM] $6.00 Gauss Meter adequate?
But read this: This is great for weak magnetic fields, but may saturate when measuring strong NIB magnets up close.  To use this with the stronger magnets, you will need to keep the magnet about an inch away from the Hall device
And the Bowman device has the magnets so close together so that we need a device that can handle close contact, not an inch.

Create A Jig to Space the Magnets for Testing

Sent: Monday, December 29, 2003 6:15 AM
Subject: Re: [PES_BMM] $6.00 Gauss Meter adequate?

I would think that you could create a jig in which to insert the magnets to measure them at a specific distance from the probe.  I would be curious to see which technique would be more accurate: that way, or the way that is presently described on the instructions page of using a torque wrench.
My guess is that you could get more accuracy with the Gauss meter.

Looks Good

From: Ken Rauen
Sent: Wednesday, December 31, 2003 12:13 PM
Subject: Re: $6.00 Gauss Meter adequate?

Looks good.  I recommend this method.
It can be calibrated with a good oscilloscope and a coil of wire and a sizeable bar magnet.  The face of the magnet with the flux eminating from it should be bigger than the coil to be swept over the surface.  Uniform motion by your hand is key to a decent calibration.  The exact speed of your hand is unimportant.  Use the scope to view the voltage from the thin coil.  I recommend just a 10 turn coil of enameled wire 1/2" in diameter.  Sweep it over the face of the magnet, even starting and ending the motion beyond the magnet.  You will see a rounded pulse waveform, almost squared off.  The time of the pulse and the length of the magnet face crossed tells you the speed of motion.  By the number of turns and the peak voltage that is somewhat constant, you can calculate the number of flux lines crossed.  I do not have the equations handy, but have done this in the past.  10% error is a halfway decent calibration for B flux of the magnet face.
Good luck.

$6.00 Gauss Meter and Bowman Motor Application

Sent: Saturday, January 03, 2004 12:01 PM

Hi Sterling, I have come up with wonderful ideas on how to use that cheap $6 gauss meter. See if Douglas approves it.
First you have to incorporate the Hall pickup into a end of a small plastic tube and cable the leads out of the tube to the circuit board. Now we can place or point the Hall device in the exact small area we want with this home made pickup probe
Next take all seventeen Bowman magnets and measure the value at only the NORTH pole ends never moving the pickup all this time and keeping the same distance from the pickup probe to each magnet.
We select eight magnets that have the same or nearly the same NORTH pole readings and mount them into our drilled MAIN plastic rotor. All NORTH poles facing one way. 
Mount this MAIN rotor on a shaft BY ITSELF so it can be rotated and place the Hall pickup probe in the same CENTERED position you would normally have the SOUTH pole of the actuator magnet positioned. Secure the Hall probe there so it does not move.
Check the value you have on the first magnet in the rotation. By pushing the magnet back and forth in the plastic rotor try for the smallest value you can get. This is going to be the ZERO or NULL value.
Do the same for every magnet on the main rotor as above.
WITHOUT TOUCHING THOSE MAGNETS swing the probe next to any magnet NORTH end and secure the probe in this fixed position.
Now ROTATE the main plastic rotor and check that each NORTH value of every magnet that swings by is the same or very close in value.
WITHOUT MOVING ANY MAGNETS ON THE MAIN ROTOR - secure each magnet PERMANENTLY so it does not move. 
Check the NORTH pole values you found in the remainder of your magnets you have left. Select any four magnets with the same or nearly the same value and place them in the repel rotor drilled holes. NORTH poles facing one side. That is the side we will measure.
Place the rotor with magnets in them BY ITSELF on a shaft so it can be rotated. Place the hall pickup probe close to any NORTH pole magnet end and secure in a fixed position.. Observe the reading. Next rotate the rotor and check that this reading is the same for all four magnets. Any magnet can be adjusted by sliding it back and forth in the plastic rotor.
WITHOUT MOVING ANY MAGNETS - you can now secure each magnet PERMANENTLY so it does not move.
Take the four remaining magnets you have left and mount them into the drilled plastic attract rotor. This time we are going to measure the SOUTH poles the same way as the Repel rotor north pole magnets were  measured.  Adjust each magnet the same way as in the Repel Configuration. Secure the magnets the same way.
With mounted magnets SECURE in ALL rotors the FORCES with the smaller rotors to push through or pull away from the main rotor should be adjusted EQUALLY. If correctly done  the repel rotor magnets will be closer to the main rotor magnets while the attract rotor setup will be further away.
You are now free from having to play with individual magnets that will push or pull out of rotor positions while you are trying to adjust them.     
All above procedures a brainstorm by Tom Ferko


From: Ken Rauen
Sent: Sunday, January 04, 2004 11:45 AM

Sounds fine to me.

From: Eric Vogels
Sent: Friday, January 02, 2004 6:33 AM
Subject: [PES_BMM] 6 $ Gauss meter really works.

I received the parts today and I made the Gauss meter. And it works.
Although a spacer is needed when using with NEO's. I also used a breadboard circuit (like the one on the website) but now I know that it works I'll make
a nice box around it.
I didn't buy a calibrated hall sensor but I made the gauss meter as a compare device. And that should work.

From: Mark Hayton
Sent: Tuesday, January 13, 2004 10:45 AM
Subject: [PES_BMM] Bell 640 Gauss Meter on Ebay.. Could be a good deal

F.W.Bell 640 Gaussmeter
Measurement range is from 100 G to 30 kG full scale in 10 dB steps. Measures DC and AC (up to 400 Hz).
Requires 3 prong round power cord.

You can buy it now for $144.95

[a source] [Google > Bell 640 Gaussmeter]

From: A.S. [Engineer]
Sent: Friday, February 06, 2004 12:29 AM
Subject: Re: $6.00 gauss meter
This is fine.  It's really just a probe, not a meter.  The accuracy and linearity, and temperature sensitivity of the linear hall sensor makes it useful for taking approximate readings.
From: Mark Hayton
Sent: Wednesday, February 11, 2004 8:46 AM
Subject: [PES_BMM] Re: flux line direction indicator

I received my MagnaProbe today, very, very cool, it really helps to see the fields in action.


See also


Page posted by Sterling D. Allan Jan. 4, 2004
Last updated November 06, 2004
 visits since Jan. 11, 2004

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