Load cell positioning and mounting questions

[Cptnyar77]

Hi there. So I have printed the "single" version. The load cell seems to fit on the bottom as pictured, but my question is:
What do you use to keep it in place and what is the small groove for that is slightly wider than the load cell?

[GeekyDeaks]

What do you use to keep it in place

The plunger should rest upon the upper part of the load cell and when the whole piston is re-assembled, the spring will provide a small amount of preload to keep everything from moving around.

what is the small groove for that is slightly wider than the load cell?

I am not sure what you referring to, could you please elaborate? The widest groove in the middle of the opening is the one that allows the load cell to be inserted into the assembly so that it can drop down into it's resting place at the bottom. There gaps in the model above to allow the load cell to be inserted and below to allow the load cell to deform. Does this help?

[Cptnyar77]

Thank you. My load cell was smaller than the one designed for.

Next question the schematic shows 4 leads from the load cell but there are only 3 leads. Advice?

[GeekyDeaks]

Ah, yeah that is not super clear. It's pins 2 ,3 and 4 on the circuit diagram (Vin+, Vin- and V+ with respect to the amplifier pins):

The load cell is used as the upper part of the wheatstone bridge. The resistors on the PCB are used to construct the lower section of the bridge.

[Cptnyar77]

OK couple things.
1.) My g27 reads 5v (4.9) at the pin? Is this normal?

2.) I opted to go with a 4558 for the op amp (I have a bunch laying around from building guitar pedals.)
Is this a bad choice?

3.) I can't seem to get this working with a single/balancing the wheatstone BUT it works just fine if I use two load cells.
My issue here is that my load cells are shaped slightly different. Would you be willing to share the model (single_holder.stl) in an editable format so I could try my hand at making these fit?