SparkFun Load Sensor Combinator

If you have ever opened an electronic bathroom scale, you were likely greeted by a confusing tangle of 12 different wires. The SparkFun Load Sensor Combinator is a bare PCB designed specifically to eliminate that mess of complicated wiring for four individual 3-wire load sensors and combine them into a standard, easy-to-read four-wire Wheatstone bridge configuration.

Hacking & Remote Sensing

This board's versatility allows you to mount four individual sensors for a custom base, or simply gut an off-the-shelf bathroom scale to hack this combinator inside. As you may have noticed, it's packed with footprints to make your load sensing project customisable and scalable:

• Direct Amplifier Connection: The five pins on the edge of the combinator line up directly with the SparkFun Load Cell Amplifier Breakout, making your initial wiring with the most important board needed to get started a breeze.
• Long-Distance RJ45: If the electronics you're incorporating need to be placed far away from the physical scale (and you don't want to go wireless), the board includes an RJ45 footprint. This allows you to route the four Wheatstone pins (and a shield pin) through a standard twisted-pair Ethernet cable.
• Remote Temperature Tracking: We also included a footprint for a DS18B20 one-wire temperature sensor. Because temperature variances can affect load readings, this allows you to gather environmental data right at the measurement site and transmit it over the same Ethernet cable.

Community Updates & Wiring

We are always listening to user feedback, and this version features a few specific community-requested updates. We improved the silkscreen to clearly read "C/+/-" (replacing the old "R/W/B" labels) to reduce wiring confusion, and we moved the temperature sensor connector safely away from the standoff hole to make mounting much easier.

Please be aware that this combinator is strictly designed to work with 3-wire load sensors and is not compatible with 4-wire load cells.

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