Load cell amplifiers

In simracing pedals load cells are often used for the brake pedal.
They provide a realistic feeling and like a real hydraulic brake the signal increases with the force applied. A challenge in DIY setups with load cells is to amplify and shift the tiny signal from the load cell.
Depending on the type of load cell it is either a full wheatstone bridge creating a differential signal or in the case of 3 wire load cells just half of the wheatstone bridge which is basically just a resistor divider changing the ratio with the force applied to the strain element.

Using 3 wire load cells alone on a differential amplifier requires generating the other side as a reference voltage with a static divider. In some applications a 1k/1k divider can be enough but then an offset either positive or negative is to be expected.

Another solution is to use a variable divider as the reference. This is what i chose for the following module. It features an INA333 and a trimpot for the gain and also one for the offset to fine tune the loadcell depending on preloading and manufacturing variations.

The module can be purchased on Tindie and schematics are available on GitHub