SparkFun Load Sensor Combinator

The SparkFun Load Sensor Combinator is a bare PCB that combines four load sensors into a standard four-wire Wheatstone bridge configuration. If you open up an electronic bathroom scale, you’ll find a large rat’s nest of wires. The Load Sensor Combinator was created to combine the 12 wires found in a bathroom scale into the standard four-wire Wheatstone bridge configuration.

This version of the SparkFun Load Sensor Combinator features a few changes that you specifically asked for! We updated the silk on the breakout to read “C/+/-” instead of “R/W/B” and moved the temperature sensor connector away from the standoff hole.

You can either use four individual load sensors or simply purchase an off-the-shelf bathroom scale and hack the combinator into it rather than trying to design a base to properly mount four load sensors.

This board works great with our Load Cell Amplifier breakout board; the five pins on the edge of the combinator line up directly to the five pins on the amplifier.

If your amplifier and supporting electronics are more than a few inches away from the scale, an RJ45 footprint is provided. The four Wheatstone pins (E+/E-/S+/S-) as well as the shield pin are connected to twisted pairs within a standard cheap Ethernet cable. This allows the amplifier board to be placed many feet away from the scale itself.

The combinator board also includes a footprint for the DS18B20 one-wire temperature sensor. This allows the user to gather the temperature of the scale in case there is a large variance between the scale and the amplifier. These three pins are accessed through the RJ45 connection as well, allowing remote temperature readings to be gathered over one twisted pair Ethernet cable.

Documents:

• Schematic
• Eagle Files
• Hookup Guide
• Getting Started with Load Cells
• GitHub