Yet Another Gaussmeter

[David King]

Bitch slapping sounds like fun. How do I become an armchair developer?

If you think the Arduino platform is cool, you might also want to check out something the Brits came out with that's basically the same but cheaper to implement and less mac friendly called PICAXE.
PICAXE
PICAXE - Wikipedia, the free encyclopedia
Programming can be done in BASIC. This is the one where the USB cable costs you $29 because it normally takes a serial port...
Add a serial port to your Mac

[Dave Kerr]

[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]

-drh

What self-respecting coder adds comments? My stuff's so clean, it's self-documenting.

[David Schwab]

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

Actually they are white now. They stopped doing the color stuff years ago. I haven't had to buy a single USB cable. I seem to accumulate them when I buy USB stuff.

[David Schwab]

[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]

Looks a bit like Apple Script.

Cool stuff.

[peskywinnets]

Great work!

I still think the simplest/cheapest implementation of a gaussmeter bar none**, is to buy a Pickit2 programmer (or a clone eg - Clone PICKIT2 PICKIT Microchip PIC Programmer Kit on eBay (end time 06-Feb-10 14:39:10 GMT) - which within its accompanying programmer app software integrates with the pickit2 h/w to provide a USB/USART LINK usart interface - use that as the 'interface' between a little CUSTOM board and your PC - Voila THE pcb is powered by 5V USB (no PSU needed), minimal components (pic, hall sensor and a couple of caps), watch results on a PC monitor (no little LCD needed), use the pc keyboard for switching/entry (no switches needed)....just one USB cable needed.

About 20 lines of PIC code (AtoD the DC voltage from the hall sensor, turn the result into gauss terms - job done!)

total cost....$30, Oh yeah, you get a PIC programmer thrown in for free with such a gaussmeter implementation!


**PC required!

[RedHouse]

Salvarsan, I'm glad you broke the ice on alternative gauss meters. I wanted to post pics of my development a while back but didn't want to step on any toes if you know what I mean. I too have one in the works, attached are the pics of my prototype.

"Like minds" I suppose, as I too have the current and peak gauss displayed at the same time (mine is on different lines though).

Started in PicBasicPro, then switched to MicroC Pro. Used the PIC 16F886 at first then switched to 18F2620 last month.

I opted for the 5-button navigation scheme like a TV remote or MP3 player uses, all functions have on-screen prompts so there's no need for a user manual just to use the meter, it leverages users existing knowlege.

Prototype has both internal probe (the black lump on the front end) and an external probe with a locking 3.5mm plug, the internal one is the AD22151 and the external is whatever one wants. Holds 3 probe setting/calibrations right now but might roll that back to two like Elepro did.

In the pic, it shows P2 which means probe-2 is selected, the (H) and (Z) are "hold" and "Zero". Pressing the OK button gets you into the menu.

I'm not going for cheap-to-build, I'm going for a professional (retail) offering to sell under my Classic Amplification business name.

[David Schwab]

Nice work Brad!

[Arndawg56]

Salvarsan, I'm glad you broke the ice on alternative gauss meters. I wanted to post pics of my development a while back but didn't want to step on any toes if you know what I mean. I too have one in the works, attached are the pics of my prototype.

"Like minds" I suppose, as I too have the current and peak gauss displayed at the same time (mine is on different lines though).

Started in PicBasicPro, then switched to MicroC Pro. Used the PIC 16F886 at first then switched to 18F2620 last month.

I opted for the 5-button navigation scheme like a TV remote or MP3 player uses, all functions have on-screen prompts so there's no need for a user manual just to use the meter, it leverages users existing knowlege.

Prototype has both internal probe (the black lump on the front end) and an external probe with a locking 3.5mm plug, the internal one is the AD22151 and the external is whatever one wants. Holds 3 probe setting/calibrations right now but might roll that back to two like Elepro did.

In the pic, it shows P2 which means probe-2 is selected, the (H) and (Z) are "hold" and "Zero". Pressing the OK button gets you into the menu.

I'm not going for cheap-to-build, I'm going for a professional (retail) offering to sell under my Classic Amplification business name.

Let me know when I can purchase one. I'll sell my other one.

[Possum]

....

Very nice. I like the built in sensor with addition of external. Is is possible those thingys can have a glitch where they lose their programming? How are the AlphaLab gaussmeters done? Stay under $100 and you might have a sale here....

[salvarsan]

Salvarsan, I'm glad you broke the ice on alternative gauss meters. I wanted to post pics of my development a while back but didn't want to step on any toes if you know what I mean. I too have one in the works, attached are the pics of my prototype.

For similar reason's, if all I post is a crude prototype, it is no threat to Elepro's fine efforts.

Started in PicBasicPro, then switched to MicroC Pro. Used the PIC 16F886 at first then switched to 18F2620 last month.

There are cheap PIC 18Fxxxx chips with 12-bits A/D
which would simplify the data smoothing some.
Do you have any plans to use a higher rez PIC?

"Like minds" I suppose, as I too have the current and peak gauss displayed at the same time (mine is on different lines though).

It's too essential to leave it out.

I've also coded a "dead zone" at 0 gauss +/-2 so the display doesn't bobble around.

For maximal laziness, the peak reading self-clears if the sensor sees zero gauss for two seconds.

Anyone is free to incorporate these ideas.

opted for the 5-button navigation scheme like a TV remote or MP3 player uses, all functions have on-screen prompts so there's no need for a user manual just to use the meter, it leverages users existing knowlege.

I assume that many users are dumb as a box of rocks and design for the most
obvious functionality requiring no more user input than to power up the device.
Remember Occam's Law: Keep It Simple, Stupid.

Prototype has both internal probe (the black lump on the front end) and an external probe with a locking 3.5mm plug, the internal one is the AD22151 and the external is whatever one wants. Holds 3 probe setting/calibrations right now but might roll that back to two like Elepro did.

I'd be interested in swapping ideas about the AD22151.
Do you bother with much temperature compensation, or simply stay with the vanilla
bipolar mode application?

By "calibrate", do you mean to observe the sensor's output from a known field strength?

The Principle of Maximum Laziness compels that I state the sensor's worst case
accuracy and simply live with it.

I'm not going for cheap-to-build, I'm going for a professional (retail) offering to sell under my Classic Amplification business name.

Yup. I'm impressed with your execution, you bastard.

My goal was to make a stupid-simple toaster of a gaussmeter
and put it out under a Creative Commons license while building a
more capable one for sale.

-drh

[mkat]

What self-respecting coder adds comments? My stuff's so clean, it's self-documenting.

So is mine (signature is the exception, not everyone's a code cutter). When you're working with large apps, the last thing you want to see is streams of comments which may or may not be updated LOL - the code is the source of truth. But still, I like

gauss -= calibration;

better than

gauss = gauss - calibration;

[salvarsan]

What self-respecting coder adds comments? My stuff's so clean, it's self-documenting.

I wrote that so the non-programmers could get
the gist without their eyes glazing over.

Otherwise, I might put the conversion+calculation into
the display argument so as to minimize static RAM use.
This is rather more important on a chip with only ~1k SRAM
if you plan to use printf() or scanf() later on.

[B]loop() {
   lcd.setCursor(1,0) ;
   lcd.print((((analogRead(1) - cal0) * 10) / 13)) ;
   delay(250) ;
}[/B]

-drh

[salvarsan]

Let me know when I can purchase one. I'll sell my other one.

You could simply ask Elepro for some more features and
buy the upgraded chip for less than a whole new gaussmeter.

I don't think Elepro is done with it.
Programming is in his blood.

-drh

[Possum]

...

I wouldn't buy a gaussmeter that doesn't read real numbers, then its not a gaussmeter but only reads relative strength, not gauss. I think if you actually wanted to sell them that would number one priority as well. Somewhere on the net there are instructions for building a gaussmeter using a Radio Shack hall sensor that is calibrated, you might try to find that to see how calibration is done maybe...

[-Elepro-]

wow ... this is the thread of news on gaussmeter world !!!

but did you use 10bit a/d without any kind of oversample or average? did yo display the result of a single sample? did you use same math for normal and peak hold mode?

lcd.print((((analogRead(1) - cal0) * 10) / 13))

where do the remainder of divide go ?? for eg, if the result is 10.99 it display 10? or in your library there's a self-rounding?

my little suggest is if you want really understand the mcu programming start with use the assembler language.... just with it you can really understand what happend inside the mcu because it is the mcu language.... you will can use c++ later and for most complex firmware....


btw, now it's my turn:

all features of previous version
64 samples in peak hold mode and 1024 in normal mode
2 probe with calibration accuracy of 0.000001volt/gauss ...
no more 70''s like switches and wires (all functions controlled by onboard tactile buttons..... power and backlight included)
double side probe (ad22151 a1302... or other)
average mode with 5sec averaging (for whole magnet measuring)
onboard usb-con for probe
professional pcb 2side-silkscreen-soldermask (the stripe on right is to make probe)
bla bla bla etc etc

here's project and prototype

bye