TrailerTrash:
$0.99 50 x Resistors 250 Ohms OHM 1/4W 5% Carbon Film
$0.99 50 x Resistor 10K Ohm 1/4W 0.25W 5% Carbon Film
$0.99 3 x 0.1uF 50V Radial Capacitor Tantalum
$14.28 2 x INA122 Precision Instrumentation Amp, 2-36Vsup R-RO
Total: $17.25
worth it?
As Lefty say's, 'priceless', though one has to wonder why on Earth, or in your case 'a rogue planet called Nibiru' would you design a circuit with a precision op-amp costing $14 and buy for less than one dollar, 50 resistors that are a inferior 5% carbon film?
I can see that the two 10k? resistors probably do not need to be exactly 10k?, but for me, it's about good design practice.
Out of the 48 resistors left over, a time will come where you wished you had 1% metal.
Chagrin:
What you'll find is that when the cell is at rest it will report some non-zero voltage (load cells are never perfectly balanced), and then you'll want to get the largest voltage swing possible from that point when load is applied. You'll be doing a lot of fiddling with the gain resistor when you're setting this up and will want to have 500R or 100R or maybe even 10R trimmers on hand to do that.
too late, i bought all the stuff already
you think i should replace the 250ohm resistor with a 250k ohm Trimmer Potentiometer? but they have 3 pins. draw it.
Chagrin:
What you'll find is that when the cell is at rest it will report some non-zero voltage (load cells are never perfectly balanced), and then you'll want to get the largest voltage swing possible from that point when load is applied. You'll be doing a lot of fiddling with the gain resistor when you're setting this up and will want to have 500R or 100R or maybe even 10R trimmers on hand to do that.
too late, i bought all the stuff already
you think i should replace the 250ohm resistor with a 250k ohm Trimmer Potentiometer? but they have 3 pins. draw it.
And ordered one. With that kind of resolution one can directly read low level wheatstone bridge devices without requiring amplification at all. Lets see how good it's low noise performance is when it arrives.
Hey! As fate would have it; I am currently a scale technician--previously worked on helicopter's that towed stuff (they're pretty cool) technician--and I found Arduino, explicitly from my interest doing this same project. How has it turned out? & "what-all" have you pieced together to get it done?
I have lots of experience on the hardware and end-market commercial software for scales;
