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Magnetic field array

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LAN_403

Tesladownunder

Sun May 28 2006, 05:29AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

For an afternoons entertainment I made this. It contains 20 UGN3503 Hall effect devices. They output 2.5 V in no field. Present a south pole and voltage goes up by by 1.3mV/gauss and the same in the reverse. (10,000 gauss = 1 Tesla).

So what did I put on the other side? I would be interested to see what other people would do.

I got 50 of these from eBay and have yet to put the rest in but the concept works. Pics after I get a few replies.

Peter

Bjørn

Sun May 28 2006, 06:17AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

20 LEDs on the reverse would do nicely. Since they are quite fast putting them in a row on a spinning disk would be good.

Tesladownunder

Sun May 28 2006, 06:31AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Close but I wanted to indicate field intensity and direction. Spinning disk is a good idea and I have considered this as well. It has the big advantage of giving an analogue smoothness and with a sufficient number of lines should read out with good resolution but with the disadvantage of the mechanics.

Any other suggestions?

Peter

Bjørn

Sun May 28 2006, 06:45AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

20 more LEDs of a different colour in antiparallel should give the polarity. Something that could show different frequencies would be a good addition.

Tesladownunder

Sun May 28 2006, 06:55AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

That is what I hoped to do but it appears to be a voltage source only not sink. Only really space for 2 standard LED's behind each sensor so it can't be too complicated. (IQ<< 135 in my clan).

One more go.

Peter

joshua_

Sun May 28 2006, 07:50AM

Registered Member #61 Joined: Thu Feb 09 2006, 05:50AM
Location: Mountain View, CA
Posts: 43

Hmmmm... I'm interested to see what happens with this one. My initial hunch is varying forward voltages on the LEDs meaning that <2.5v is one color, and somehow >2.5 would mean that the ohter color would light up instead... Perhaps in parallel sitting behind a resistor? It's a little late for my brain right now, but whatever it is, I wanna see...

Carbon_Rod

Sun May 28 2006, 08:17AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Comparators are simple. But IIRC the classic LM2914 is a 10 pixel linear bar graph (they sell cheap pre-made car audio level display meters with the LEDs already wired and mounted.)

Personally I would prefer to scan the states with an AD unit and use a built-in graphics lib to give a keen display as a crude 2d plot or a slowly revolving 3d plot -- Clean , simple, and adaptable.

Cheers,

Tesladownunder

Sun May 28 2006, 08:24AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

My brain was hurting too but I had available 50 red and 50 green LED's with dropping resistors. The simplest I could get to indicate the three states was to do as you suggested, that is to use the different voltage drops of the two colours. This is not an ideal display but gives the following. Not much room to do much else as you see.

North pole: no lights
no Field: red
South pole: red and green

1148804685 10 FT10275 Magarray20frontangled

1148804685 10 FT10275 Magarray20topnomagnet

1148804685 10 FT10275 Magarray20nibnorth

1148804685 10 FT10275 Magarray20nibsouth

Bored Chemist

Sun May 28 2006, 09:16AM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Thta's quite a nice "work-around" as well as a nice toy. Do you actually have any practical use for it?

Tesladownunder

Sun May 28 2006, 10:30AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Actually I had vague plans for looking at the can crusher fields. The UGN3503 is rated as linear to 23kHz and the can crusher runs at a resonant frequency of about 16kHz. Have to be careful not to fry the array or pull it apart as the LED leads are magnetic.

Here are two pics with the array moving by hand in a time exposure shot of 3 secs with magnets below the plastic sheet. Hand is faster than the eye here.
The first one is of a single pass with the south poles of a ferrite ring and a stronger NIB magnet adjacent. The second pic shows the "hole" where the NIB has been turned north up. You can see my foot stationary here for 3 seconds which gives you a clue as to my dancing style.

Peter

1148812219 10 FT10275 Magarray20movtsinglepassends

1148812219 10 FT10275 Magarray20movtsinglepassns

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