Yet Another Gaussmeter

[salvarsan]

First pass on a cheep? gaussmeter using the A1302 Hall Effect Sensor,
an Arduino 2009 microcontroller, and an LCD daughterboard or "shield".

That's a 5/8" x 3/16" dia pole magnet held against the sensor.

The assembly was not difficult, consisting of inserting the A1302 into
socketed pigtail leads and inserting the LCD shield.

Bill of materials:
Arduino - $30,
LCD shield - $20
A1302 - $1.50
misc.: leftover pigtail from CD burner, USB 'B' cable - $0.00

Grand Total is $51.50 for all you Van Halen fans.

Before you folks start slinging shit at it (in the finest of Internet traditions),
remember that it is the first pass (actually, there was a zero'th pass a
year ago which had no display but sent data by USB stream).

All hardware was purchased assembled and tested.
All development used Open Source software running on Linux.

There is no power bypass cap across the sensor, nor does it
have a compensation cap on its signal line -- it is noisy!

-drh

[-Elepro-]

fine work
why there are 2 values displayed?
what language you use?

bye

[David King]

OK -now where's my Ver .01 Extech?

[Possum]

...

What does it actually do? How much guass, how is it calibrated? Can I watch iPod movies on it?

[salvarsan]

The left value is immediate gauss, the right one is the peak reading.
This is a prototype, not a finished product.
The display needs a better user design so
you won't need to ask basic questions.

The firmware implementation is in C/C++ using the Arduino IDE and libraries
which use the GNU AVR compiler suite and libraries. It makes development
very easy, very inexpensive. Mille grazie, Massimo Banzi.

What does it actually do?

It's a f*cking gaussmeter.
I measure small magnets with it,
but have no suggestions for how
other people may use it or
where they might install it.

Given that it uses the A1302 sensor, it's good for about +/-1700 Gauss
and is spec'd at 3% worst case accuracy over the full scale.

It self-calibrates if you hold it away from any magnets and press RESET.
This is a prototype, not a finished product.

The hard work will be a power-down/sleep mode so
that it can be used with batteries.

The Arduino is an Atmel (AVR) Atmega328 8-bit RISC device running at 16MHz.
There is a PIC 18F2550 work-alike called the Pinguino at HackingLab, and a 32-bit
ARM7 in the shield form factor Coridium Corporation - ARMmite PRO Controller

More Arduino info
English: Arduino - Wikipedia, the free encyclopedia
Italiano: Arduino - Wikipedia

The official Arduino site:
English: Arduino - HomePage
Italiano: Arduino - HomePage

-drh

[Possum]

...

What technical spec is "f*cking" do you have to stick it in something with lubricant? Well there are guassmeters that use hall sensors like one I built that all it did was measure gauss, not calibrated, and the readout was a multimeter, 600 guass was about its limit, so just wondered what yours does. I still would like one I could watch iPod porn on and brush my teeth with, wait that sounds yukky, never mind....

[salvarsan]

What technical spec is "f*cking" do you have to stick it in something with lubricant?

It may be close to the implied point of installation

.Well there are guassmeters that use hall sensors like one I built that all it did was measure gauss,

All it does is measure Gauss

not calibrated,

it's only calibrated at 0 (not full range)

and the readout was a multimeter,

the readout is an alphanumeric LCD (means: doesn't need a multimeter),

600 guass was about its limit,so just wondered what yours does.

+/-1700G (give or take),

also displays peak values,
also sends the measurement out the USB port.
Those are the functional benefits and features.

For DIY, it still looks good since it uses off-the-shelf
pre-assembled modules, and needs only three solder connections for the sensor.

That's only the prototype rev. 0.1

Geez, you expect a lot for $51.50.

(pout, sniffle)

-drh

[David King]

Well I'm impressed! I like the dual, simultaneous readings. Very well done and hats off to Arduino foundation etc. I just wish I was smart enough to do something cool with all these new DIY toys.

[salvarsan]

Well I'm impressed! I like the dual, simultaneous readings. Very well done and hats off to Arduino foundation etc. I just wish I was smart enough to do something cool with all these new DIY toys.

I was thinkina coding the display so it would be more obvious, like

Gauss __ MAX
N 666 __N 712

For pickup magnets, a gaussmeter only has to be as convenient as
a compass yet give a useful numeric result.

It's not really a tool until it has a case, though.

-drh

[ShannonH]

I was thinkina coding the display so it would be more obvious, like

Gauss __ MAX
N 666 __N 712

For pickup magnets, a gaussmeter only has to be as convenient as
a compass yet give a useful numeric result.

It's not really a tool until it has a case, though.

-drh

Nevertheless, that is very cool, and would be quite useful.

[David Schwab]

For DIY, it still looks good since it uses off-the-shelf pre-assembled modules, and needs only three solder connections for the sensor.

Well it doesn't get simpler than that! The module comes programed as a gauss meter?

Nice work.

[David King]

David, Arduino is a platform, you just dump code into it via a USB cable from you PC (Mac too but you need a different cable I think). The code is open source but you might need to customize it. There are all sorts of off the shelf dohickies you can plug in like stepper and servo drivers for robotics etc.

[David Schwab]

Ah! If I had actually looked at the links I probably would have figured that out.

That's very cool though.... I love gadgets.

So where did the gauss meter code come from?

Also Macs use standard USB cables.

[Steve Conner]

Also Macs use standard USB cables.

No, they use stylish colour coordinated ones that cost more.

I try to stay out of the Pickup Makers board, but this was too cool, I was just reading about Arduinos today. I recently got a Mac, and Arduino is about the only embedded development platform that works on MacOS. It's also very cool how you can program them in C++. I've used assembler on PICs for years, but the Arduino looks like it would be a really handy tool for prototyping and one-off jobs.

Where did the gaussmeter code come from, well I assume Salvarsan wrote it, but he's too modest to say. Or wants to avoid the usual internet bitch slapping from armchair developers.

[salvarsan]

Arduino fails to suck

No, they use stylish colour coordinated ones that cost more.

"More?" In Apple context, "more" means 2.5x $.

I try to stay out of the Pickup Makers board,

Screwed the pooch on that one, didn't you?

...but this was too cool, I was just reading about Arduinos today. I recently got a Mac, and Arduino is about the only embedded development platform that works on MacOS. It's also very cool how you can program them in C++. I've used assembler on PICs for years, but the Arduino looks like it would be a really handy tool for prototyping and one-off jobs.

Arduino hardware is cheap & abundant,
the development IDE free, as in free beer,
but that's only part of it.

Where did the gaussmeter code come from, well I assume Salvarsan wrote it, but he's too modest to say. Or wants to avoid the usual internet bitch slapping from armchair developers.

I wrote it.

If you are a C/C++ programmer, bragging about programming an Arduino
is like bragging about screwing in a light bulb, more so when you see things like
the user-contributed Arduino libraries for network sockets, DHCP, and a web server application.
Finding all that inside is humbling.

Oh yeah, the Arduino WiFi daughterboard has TCP/IP in hardware.
To suddenly discover all these cool toys is to feel like Rip Van Winkle.

It is insanely simple to program on the Arduino because the Arduino code libraries
hide the very ugly details of microcontroller hardware better than anything I've ever
seen in 20 years. It's so bonehead simple that the gaussmeter essentials look a lot
like this:

[B]loop()
{[/B]
   [B] int gauss ;[/B]

    [B]gauss = AnalogRead(1) ;[/B]          // read analog/digital converter #1
    [B]gauss = gauss - calibration ;[/B]   // + is North, - is South
    [B]gauss = (gauss * 10) / 13 ;[/B] // scale for sensor 1.3 mv/gauss

    [B]lcd.setCursor(1,0) ;[/B]        // set LCD cursor at row 1, column 0
   [B] lcd.print(gauss) [/B];          // print out gauss on LCD

    [B]delay(250);[/B]                 // pause for 1/4 second
[B]}[/B]

Well, it looked like that until I added in oversampling, self-calibration, dead spot
stabilization, peak value display, peak self-clearing on timeout, blah, blah,
but you get the point -- You can test a project idea very quickly.

-drh