digital scale weight sent to arduino

[tayexdrums]

I am a pretty healthy guy which means I weigh myself frequently to track my progress. I was thinking one day as I was stepping on it, what if I could send the data(my weight) to a file and then do something with it such as averaging or something. How would I do this? I have an arduino with an ethernet shield but i don't really want an ethernet cord running to my bathroom.lol
I am familiar with  how to get serial data from objects. Could I use that method?

[daedalus]

You can buy weigh scales from tanita that have Bluetooth links to your home pc. They are pretty good scales, have a set myself. Then its just a little bit of programming to do your rolling average filter.

If you want to make your own equivalent, then you would need to build an instrumentation amplifier to amplify the strain guage bridge in the scales, this would give you an analog value for the weight on the scales, which you could read with an arduino. Then you would have to calibrate the scales for weight, figure out how to power the arduino in the bathroom, and how to communicate out the values.

Personally I would just buy the Bluetooth scales and get on with more fun projects

[tayexdrums]

Hmm, I see. So you are saying that I can't get the data going between the microprocessor and the output LCD? Those numbers have to come from something besides the strain gauge.

[PeterG]

You may be able to perform 1 of 2 possible hacks.

First, you may be able to locate a serial output port somewhere that was used bt the factory.

Second is, you can tap into the analog signal from the load cell and output the results via serial.

I think your best option is the second choice.

Regards

[amyk]

Hmm, I see. So you are saying that I can't get the data going between the microprocessor and the output LCD? Those numbers have to come from something besides the strain gauge.

You can, but decoding multiplexed LCD drive signals (a complex AC waveform) is a bit on the difficult side.

[8086]

How frequently?

Spreadsheet and typed input seems best option to me 

[rr100]

If you wanna go for the bluetooth scale just go one step higher and get the withings scale, it will just connect to wifi directly and (assuming you have wifi already) you really don't need to do much else.

If you want to go for cheap and do it yourself route reverse engineering the display connection seems to be a good place to start (if no other obvious interfaces are available inside).
Are there any scales with 7-segment LED displays? Those would be easy to capture.

And speaking about logging, at some point I wanted to get one of those wifi webcams and log values (from a multimeter or in this case would be a bathroom scale, but it can be anything) via pictures. Some would be interesting and it would be feasible to put them by hand in a spreadsheet (for example) but I was thinking just to do command-line based OCR on them! There are already pretty decent command-line OCRs and of course enough software to do automatic corrections, cropping, etc. And I would assume it isn't hard to OCR a display with a few digits.

[Christopher]

Simple, take out the strain gauge and amplify the signal using a low-noise op-amp, then read using a 12 bit dac or something (Personally I'd used embedded 8 bit)

Also working on same thing with mini-scales. Let me know how you get on.

[T4P]

If you want a good 12-bit ADC and uC together consider the Cortex-M0 Or STM32-F0 chips

[GK]

Freaking heck. I wonder when someone is going to stick a Bluetooth thingo into a toothbrush. Your iMac or whatever could then alert you when the bristles are worn out.

Just write the damn numbers down and poke them into a spreadsheet at the end of the month.

[Psi]

Freaking heck. I wonder when someone is going to stick a Bluetooth thingo into a toothbrush. Your iMac or whatever could then alert you when the bristles are worn out.

Well we already have toothbrushes with microcontrollers so yeah, seems likely :|

[rr100]

I was actually going to suggest a teardown on a Microsoft Sidewinder X8 mouse. It has at least 4 PCBs (albeit 2 smaller ones for buttons almost unpopulated but 2 rather big, stacked on top of each other and rather heavily populated). It has a very few buttons more than your usual mouse but still...

[T4P]

I was actually going to suggest a teardown on a Microsoft Sidewinder X8 mouse. It has at least 4 PCBs (albeit 2 smaller ones for buttons almost unpopulated but 2 rather big, stacked on top of each other and rather heavily populated). It has a very few buttons more than your usual mouse but still...

And very expensive