Help for developing a bathroom scale that logs everyday data

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#1
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Hello :-)

I was thinking that I would like to have a weighing scale to have on my bathroom so I can log my weigh... I am a bit over my body average, I am trying to get on the line, mainly because of my health and also look ;-)

I was thinking If I can found one on market, but I didn't... If someone can point me to a ready solution...

Since I believe it can be difficult to find it on market, I was thinking of what I need to make one for me, DIY, using an AVR and share the project on Code.Google (with purposes to get help from others and also help others in my situation) :-)

Can someone give ideas? as the sensor to use... the communication to PC..., etc...

I am recently using an AT90USB162, I am able to use MyUSB Lib.

I am imagining some kind of contactless card for storing the data, when I use weighing scale leave the card near it - weighing scale storing automatically the date and weighing.

On PC having a contactless card reader where I could read a file maybe of that with coma separated in TXT, so on OpenOffice I could make a graph :-)

I never worked with contactless cards... - I work on electronics with AVR, I am always looking for new projects for learning ;-) :-) -- I would like to start using the AVR32 :-)

Thank you :-)

JPCasainho,
www.Casainho.net
.Portugal

Last Edited: Sat. Jul 19, 2008 - 08:32 AM
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For an industrial project, I am interfacing to a digital scale that has an RS232 interface. With that you can grab the information from the scale and do with it what you like. It may be a bit pricey for you, though, at about US$200.
http://www.balances.com/
http://balance.balances.com/scal...
http://balance.balances.com/scal...

I'd think you could find similar models readily available in Europe as I looked at a brand that was of Italian manufacture, and one that was German.

If you are REALLY large, then on eBay in the results for "scale rs232" you find
http://cgi.ebay.com/Salter-Breck...

;) Lee

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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theusch, thank you for your suggestions. However I was looking for something like a bathroom weighing scale.

Tehy are very cheap... maybe I could adapt one of that cheap ones and add a sensor, after work the data on MCU and register it on some card - preferable contactless :-)

EDIT:

I found an example of use a digital Bathroom Scale at instructables.com.

Maybe If I re-use on of that cheap digital Bathroom-Scale I can easy have the sensor + the scale body. I may need to do some analogue electronic circuit to amplify the signal so it can be read on an MCU ADC.

Using a real time clock module to have data, read it using SPI bus.

Put AT90USB162 working as Mass Storage Host, to write on a pen flash memory new data each time I got to measure my weight. Pen flash can stay always connected to system to record a big chunk of data, I can take the pen flash and read that data file on computer and make a graph.

NO LCD: how to setup the data on real time clock module? - simple, put a specific file with data on pen flash, system will read data and setup that new data and delete that file - each time I need to setup new data I must put that specific file on pen flash.

JPCasainho,
www.Casainho.net
.Portugal

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Is there some way you can interface to the LCD display of the cheap scale? A long time ago, an engineer did the same thing by decoding the bits used to drive seven segment displays on something for which I don't recall, just that it was the bits for the segments.

I'll believe corporations
are people when Texas executes one.

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tubecut wrote:
Is there some way you can interface to the LCD display of the cheap scale? A long time ago, an engineer did the same thing by decoding the bits used to drive seven segment displays on something for which I don't recall, just that it was the bits for the segments.

Thats another possibility ;-) :-) -- thanks.

I was reading the MyUSB Lib Mass Storage Host example and a bit of the FAT32 File IO Library :-)

I must read more about FAT32 to know If with this 2 Libs I could read and write on a pen flash drive.

I think I would use the ATmega32U4 which have 2,5kB of SRAM - I think FAT32 are like chunks of data of 512 bytes each.

JPCasainho,
www.Casainho.net
.Portugal

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Oh, I just finished this project, and works great :-) -- I did learn a lot and I ended up by not using AVR but instead ARM7 from NXP Phillips, because it's very important for me to have a cheap, Open JTAG debugger, not like the Atmel AVRs that have closed, proprietary debuggers :-(

2 pictures:

And one video.

Here is the project page with the source code an many technical details :-)

http://code.google.com/p/casainh...

JPCasainho,
www.Casainho.net
.Portugal

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Casainho,

Nice job on your project!

JC