Thin film Hall sensor

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The distributors I approached either didn't reply to my email, or only replied once. What am I to do!? Thin film Hall sensors aren't easy to buy, it seems.

snipped-for-privacy@netzero.com Inscribed thus:

You could always salvage some from a scrap computer fan or floppy drive !

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Best Regards:
                          Baron.

They're switches, not linear. They're silicon, they're not thin and they're in a package. I didn't pick the HS-100 because it was hard to get...

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So why did you pick this device? Is there realy nothing else out there? (in grad school I made a hall sensor out of a thin piece of Bismuth. It was just for a demo though, and I had to push several amps through it to get a milli-volt signal.) What magnetic fields are you trying to sense? Is it the samll size that is important?

George H.

Hall sensors make BLDC motors a lot easier to control, at least at a hobby or small production level. Back-EMF isn't that easy to do over a wide range of motor speeds, at least the last time I looked at it.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

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It's not for motor control.

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None that I could find. Perhaps it's time to look elsewhere. Most hits were for journal articles about how someone built a wonderful thin film sensor, not for commercial parts.

Small size is vital.

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How small is small? Is there some tiny gap in which you want to measure the field? What magnetic field strength? The Earth's Field?, permanent magnets? If you give more details, maybe someone here will have an easier way to get what you want. Do you need fast response time? I've used small hall sensors that come in what looks like a flatened T0-93 package so ~0.1 inch (2-3 mm.) is to large? Maybe you could file one of them down to make it thinner?

George H.

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Thin film small. Yes.

The field created by a wire carrying 1mA DC.

Well, there's a reason I wanted to make a lapping machine out of an old hard drive... :)

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Ouch! that's gonna be hard with that Hall sensor (or any Hall sensor).... I threw out the spec sheet... ~ 10mV/kG. (?)

What's the diameter of the wire.... Calculate the B field. I get ~10^-7 Tesla 1 mm away. (But check my numbers!) That's 1 milliGauss! Forget it, the Earth's field swamps your signal, and unless you live in the middle of nowhere, then changes in the direction of the Earth's field, (due to bits of iron moving about) will swamp your signal. (And I haven't mentioned the AC magnetic fields yet.)

I use to lap semi-conductor samples by hand. Large piece of plate glass, and some fine grit Silicon carbide in a slurry.

George H.

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Yes, it's not the most sensitive... Finding rare-earth sensors is even harder. Just finding the information has already taken me to the uni library. In person! In PERSON! In 2011! :) I can trade linearity for sensistivity. But only for existing, real, orderable products!

Or it's inside a double mu-metal shield can.

No worries. It's not impossible. Just hard.

I'm planning on purchasing Ramsden's "Hall-Effect Sensors: Theory and Application".

One more expense for what was supposed to be a hobby thing.

I need a new hobby. Drinking was a hobby for a while but booze has gone up. There's a place near me that charges 15$ for an "organic" gin tonic... With Hendricks! Blargh! It tastes like cucumbers! 15$ !

I'll stick to Bombay and 2L bottles of tonic water. And limes from Super C. Even if I have to fight with the local meth heads to get to the "6 items or less" cash. (The proles at the self-checkouts just stare, slack-jawed, at the screen for far too long for my taste. And the "speed" at which they take stuff out of the cart... Just GO GO GO!!! ARGH!)

Hmm, how can you assure that everyting's "normal", so that *two* pieces you lapped will face each other perfectly?

That was my next set of questions, how to make mechanical jigs that are perpendicular, orthogonal and normal to a given surface. It's all the same thing, but I want to make sure!

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Hmm, I've never used mu-metal, but I've heard tales that if you look at mu-metal cross-eyed you have to re-anneal it.

Sounds like it. Is the milli-Gauss number about what you hope to measure? Even without the corrupting effects of the local B field it still looks like your signal will be groveling in the noise.

Could you pass the wire through a torroid and do a flux-gate/ saturation thing like Jan has been posting?

I stick with beer. A can of Genny and I'm a happy man.

Well there were these nice metal 'jigs' that were to keep things parallel. A cylinder held the work piece and a was held in a 'donut' cylinder. But we didn't really want things parallel. We were doing FIR transmission spectroscopy, after removing the back side, you wanted a bit of a wedge on the sample so wouldn't make a little Fabry- Perot cavity.

I looked through McMaster-Carr, but couldn't find one... they must not make them any more. :^)

George H.

snipped-for-privacy@netzero.com Inscribed thus:

Ah :-( I didn't realise that. Sorry !

--
Best Regards:
                          Baron.

There are few complete motor controllers on a chip type products around. MicroChip parts MTD6501C, MTD6501D, and MTD6502B for instance. These only require a microcontroller with a dedicated PWM channel to operate. These make back-emf control of BLDC motors easier by orders of magnitude. Trying to do it in software is, as you describe, a total PITA. Dave

Will this do? Size 2.0 × 3.0 mm, 0.75 mm, not as thin, but area is even smaller.

This is available in qty's of 1 at farnell.com. (order# 1521680)