I am thinking of a project that will require the ability to sense the weight of an object and feed that back to the Arduino so it can detect weight changes.
Does anyone have any suggestions as to how I could do this please?
Depends a lot on the range of weights you need to detect and the accuracy you need.
There was a flurry of threads about this a few months back. Try doing a thread search.
I don't know a lot about this area but if you just want to know when the weight has changed could you use a piezo electric transducer as a sensor?
I guess a lot will depend on the kind of weight changes you're trying to measure and to what accuracy?
see the knock example for the code behind it.
Problem with this sort of sensor is that you only get an output with a rate of change of force not the force itself.
That is if you place a weight on it you get a reading when the weight is placed on and then it goes to zero with the weight still on.
Can you say what range of weights and what accuracy you need? I found a set of electronic kitchen scales in Tesco's for about ten quid that use a strain gauge bridge for sensing weight. You'd need an instrumentation amplifier to bring that up to a level that the Arduino could accept (Analog Devices AD620).
I am looking for detecting a weight range from zero to perhaps 250g.
And how accurately? That is, how many steps must you be able to distunguish? If all you need is zero or 250g, then a microswitch will work!
I would like to measure from between 0 and 250g in increments of 1g if possible.
I am watching this thread too, so any replies will be doubly appreciated.
I think I may have found the solution. Flexiforce make pressure sensors and there is one that goes up to 1lb of pressure.
I think that might do it if I use it underneath a tray or bowl with a pointed object underneath (with a rounded off end) to apply pressure to the sensor.
Anyone have any experience of using one of these?
I was hoping for a cheaper alternative.
This requires calibration so I'm already veto-ing it.
Well please let us know how you get on.
Hi there! I've got the same problem. I need a sensor that let me measure a weight from 0kg to 30kg. Could anybody tell me how to do it?
I'm probably missing something obvious here, but couldn't you
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Get a scale, and hook up the dial display to a potentimeter (thru a gearing system)?
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Get some springs, and measure how far they're compressed/stretched?
Good luck!
I'm using a load cell and instrumentation amp in my project. I think I payed about $16.00 for the 15kg load cell off of ebay and then I purchased an INA128 instrumentation amp from mouser.com.
Here is a 5lb one for about $12.00 (Load Cell)
What exactly is a load cell and how does it work please?
Iceman - Any pictures of your project please so I can understand how you've utilised the load cell? Thanks.