OpenScale Applications and Hookup Guide

Contributors: Nate, LightningHawk
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Attaching the Load Cell

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DS18B20 external temperature sensor

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200kg load cell

OpenScale uses 3.5mm screw terminals to connect to the load cell wires and external temperature sensor. The SparkFun Mini Screwdriver fit the screws well as does the Pocket Screwdriver Set.

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Sparkfun Load Cells follow the general color convention described below

Most load cells will have a Red/Black/White/Green wire color configuration. Insert these wires into the screw terminal and tighten the terminal to finger tight. A few load cells use a blue wire in place of the green wire - don’t worry, it will still work! Load cells with a large capacity or a long connecting cable may have an additional yellow wire that is used to shield the four signal wires. If you have this wire available attach it as well.

Three wire load sensor

This load sensor has only three wires

If you are using discrete strain gauges (for example our 50kg load sensor) you will need to use the Load Cell Combinator to combine four strain gauges into a wheat stone bridge configuration. See the Load Cell Combinator Hookup Guide for more information. Openscale also has the Load Cell COmbinator built-in. The markings UL, UR, LL and LR stand for upper left, upper right, lower left and lower right respectively. Just like you would see in a bathroom scale. The C mark is for the “center tap” which is explained in the strain gauge tutorial.

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Load Cell Combinator