Application Question

[REB1102]

Does anyone know the components involved in making a device that will sound an alarm when it senses the difference between two platforms where an object can be placed on each platform. It needs to sense a difference in weight of approx 20 lbs. The working weights involved are between 60 and 150 pounds.




BeautyandtheBeast@kc.rr.com

 

[raedbenz]

go to stores and check for sensors do this job....or get strain gauges(type of sensors) and use ADC and microcontroller to know the weight..and u can do many functions with that not only knowing the more heavy object also reading the exact weight

 

[ericgibbs]

hi REB,
Looking at your weight ranges, 60 thru 150 lbs, with a difference weight
of 20lbs, I make that about 70 states, ie; 150-130, 149-129 etc...

My first suggestion would a load cell under each platform, depending upon the outside dimensions of your platform.

You would need some amplification of the load cell signal, before you fed it
into a analog to digitial convertors. Depending upon the resolution you required you may be able to use the ADC in the PIC.

You could use a 'voltage threshold window' method by comparing the outputs of the signal amplifiers, no PIC required.
Just amplify the load cell signals, sum/difference the two signals into a comparator and use the output to sound an alarm.
This would be my preferred solution, looking at the resolution you state.

You can either buy the finished load cells [ there not cheap ] or attempt to use strain gauge elements
[ I would not recommend this route, unless you have lots of experience]

Regards
EricG