load cell interfacing
Hi,
First of all you should clear up the problem with your amplifier. LM324 is not good enough opamp for such applications, however, for educational purposes may still be used.
What problem you are facing? In order to test the amplifier, you do not need a load cell, just use a resistive divider with around 10mv differential voltage and connect to the terminals marked OUT+(IN-?) and OUT- (IN+?) points. Check for the output voltage at the point marked ADC.
By the way, I have noticed some noise problem with the amplifier with pins 12,13 and 14. It was attributed to some layout problem and it was solved by using another unused amplifier from the same package.
You should also use a 4.7uF tantulum cap in parallel to a 0.1uF ceramic cap across Power supply pins close to the IC. Small capacitor values of 470pf across feedback resistors also help to avoid unexpected oscillations in the amplifier.
Since you are using on single supply, you have to make sure that all amplifier outputs swing to +ve side only, else you should use dual supplies.
Only after establishing the proper working of the amplifier you should proceed with the remaining circuit.
Regards,