digital scale weight sent to arduino - Page 1
Forum section: electronics / projects

author: tayexdrums
author_rank: Contributor
timestamp: June 18, 2012, 08:47:18 pm
content: 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.lolI am familiar with how to get serial data from objects. Could I use that method?

author: daedalus
author_rank: Regular Contributor
timestamp: June 18, 2012, 09:44:12 pm
content: 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

author: tayexdrums
author_rank: Contributor
timestamp: June 18, 2012, 10:00:11 pm
content: 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.

author: PeterG
author_rank: Frequent Contributor
timestamp: June 19, 2012, 12:30:14 am
content: 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

author: amyk
author_rank: Super Contributor
timestamp: June 19, 2012, 09:02:27 am
content: Quote from: tayexdrums on June 18, 2012, 10:00:11 pmYou can, but decoding multiplexed LCD drive signals (a complex AC waveform) is a bit on the difficult side.

author: 8086
author_rank: Super Contributor
timestamp: June 19, 2012, 09:45:13 am
content: How frequently?Spreadsheet and typed input seems best option to me

author: rr100
author_rank: Frequent Contributor
timestamp: June 19, 2012, 10:59:40 am
content: 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.

author: Christopher
author_rank: Frequent Contributor
timestamp: June 19, 2012, 01:02:37 pm
content: 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.

author: T4P
author_rank: Super Contributor
timestamp: June 19, 2012, 06:55:14 pm
content: If you want a good 12-bit ADC and uC together consider the Cortex-M0 Or STM32-F0 chips

author: GK
author_rank: Super Contributor
timestamp: June 20, 2012, 04:23:55 am
content: 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.

author: Psi
author_rank: Super Contributor
timestamp: June 20, 2012, 04:38:13 am
content: Quote from: GK on June 20, 2012, 04:23:55 amWell we already have toothbrushes with microcontrollers so yeah, seems likely :|

author: rr100
author_rank: Frequent Contributor
timestamp: June 20, 2012, 06:19:51 am
content: 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...

author: T4P
author_rank: Super Contributor
timestamp: June 20, 2012, 07:04:27 am
content: Quote from: rr100 on June 20, 2012, 06:19:51 amAnd very expensive