Wireless Scale

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Wireless Scale

Postby tuckrr » May 16th, 2016, 4:25 pm

Hello, I'm working on a project and need a wireless scale which can give real-time weight readings to my raspberry pi. I've looked at every wireless scale imaginable, but none meet my requirements:

• Always on (doesn’t turn off after 15 minutes)
• Size should be 12x24x1 or thinner. Casing should be sturdy. No LEDs required
• Bluetooth Low-Energy wireless connectivity (Connects to my raspberry pi)
• Lithium ion Battery powered. Can be recharged via micro-USB

I am looking for someone to either build or hack an existing scale so that it meets my requirements. The payment will be 200USD + Parts
Please reply here with any questions or email me directly at tuckrr@gmail.com
Thank you!
tuckrr
 
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Re: Wireless Scale

Postby k-ww » May 17th, 2016, 6:53 am

Basic questions:

1) max range in pounds, etc
2) resolution in pounds, etc
3) repeat-ability of reading
4) allowable drift with constant weight on scale [pounds, etc per hour/day etc].
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Re: Wireless Scale

Postby tuckrr » May 17th, 2016, 1:08 pm

1. Max weight 75lbs
2. Smaller resolution is better. Ideally <2g detection
3. Repeatability - should be very consistent.. Can you elaborate on the question?
4. Drift should be low.. 1g/day if possible.
tuckrr
 
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Re: Wireless Scale

Postby k-ww » May 17th, 2016, 5:40 pm

For an idea of what parameters are spec'd by load cells [the part that converts weight to an electrical signal that still needs to be amplified / converted to digital], take a look at the sensor parameters [towards middle of webpage] for this item:

http://www.ebay.com/itm/10-20-40Kg-Elec ... SwstxVRtFR

I would end up using a 40Kg or higher rated one, to allow for some leeway in what you are weighing.

I've seen low range ones screwed up because a weight was dropped instead of placed on them.

To better consider design trade-offs, what are you trying to do with the scale, and what is the environment?
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Re: Wireless Scale

Postby tuckrr » May 18th, 2016, 1:17 pm

k-ww wrote:For an idea of what parameters are spec'd by load cells [the part that converts weight to an electrical signal that still needs to be amplified / converted to digital], take a look at the sensor parameters [towards middle of webpage] for this item:

http://www.ebay.com/itm/10-20-40Kg-Elec ... SwstxVRtFR

I would end up using a 40Kg or higher rated one, to allow for some leeway in what you are weighing.

I've seen low range ones screwed up because a weight was dropped instead of placed on them.

To better consider design trade-offs, what are you trying to do with the scale, and what is the environment?

Typical load cells like the ones there will be fine for the accuracy needed. Nothing will be dropped on the scale at any time. The scale will be used to track the real-time consumption of beer. So long term there will be a heavy static load on it.
tuckrr
 
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Joined: May 16th, 2016, 3:26 pm


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