SparkFun Load Sensor Combinator

The SparkFun Load Sensor Combinator is a bare Printed Circuit Board (PCB) that ingeniously consolidates four load sensors into a standard four-wire Wheatstone bridge configuration. This eliminates the messy wiring you'd find in an electronic bathroom scale, by reducing the 12 wires typically found in such a scale into a more manageable four-wire configuration.

The SparkFun Load Sensor Combinator has been improved based on customer feedback. The silk on the breakout now reads "C/+/-" instead of "R/W/B" for easier understanding, and the temperature sensor connector has been repositioned away from the standoff hole for better usability.

With this combinator, you have the option to either use four individual load sensors or simply modify an off-the-shelf bathroom scale by integrating the combinator into it. This saves you the trouble of having to design a base to mount four load sensors.

This board is fully compatible with the SparkFun Load Cell Amplifier breakout board. The five pins on the edge of the combinator align perfectly with the five pins on the amplifier for a seamless connection.

If your amplifier and supporting electronics are positioned more than a few centimeters away from the scale, the combinator provides an RJ45 footprint. The four Wheatstone pins (E+/E-/S+/S-) and the shield pin connect to twisted pairs within a standard Ethernet cable. This configuration allows the amplifier board to be placed several meters away from the scale itself.

Additionally, the combinator board includes a footprint for the DS18B20 one-wire temperature sensor. This allows you to monitor the temperature of the scale, especially useful when there is a significant temperature difference between the scale and the amplifier. These three pins can be accessed via the RJ45 connection, enabling remote temperature readings to be gathered over one twisted-pair Ethernet cable.

Please note that the SparkFun Load Sensor Combinator is designed to work with 3-wire load sensors and is not compatible with 4-wire load cells.

The product package includes comprehensive documents, such as a schematic, Eagle Files, a Hookup Guide, a Getting Started with Load Cells guide, and a GitHub link for further support and information.