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Make a Scale with Load Cells and Phidgets


by Lucas

Introduction

I needed to make a scale for my Pet Monitoring project so I decided to document it and share it. This will be a quick article on how you can build your own scale.

The main component of our scale: a load cell

Hardware

Building

Step 1: Scale material

I chose a basic 1/2" plywood as the material for my scale. This material was cheap and provided enough stability for the intended use. I cut the pieces into 12" x 12" sections which provided me with more than enough room for the intended use.

Step 2: Placement of load cells

Draw a line 1" above the edge on each side of the plywood square.

Step 3: Mark holes for load cells

Use a load cell as a guide, and mark where you will drill holes in the plywood.

Step 4: Stack both pieces of plywood

If you stack both pieces of plywood before drilling, you will ensure you have proper alignment later.

Step 5: Drill holes

If you don't have a clamp, duct tape works well for securing the board together while drilling.

Step 6A: Install load cell

It is important to use nuts or spacers to create room between the plywood and the load cell so that flexing can occur. Two nuts may have been overkill in this situation as there is plently of room below the load cell.

Note: Orientation

Make sure the load cell has the correct orientation.

Step 6B: Install load cell

Ensure your load cell will be able to handle the force that is applied.

Step 7: Finish installing load cells

Use the same method to install the other three load cells.

Step 8: Add top of scale

Using the holes drilled earlier, simply attach the top piece of plywood to the bottom with a bolt.

Scale complete:

The scale is now complete. All we have to do is wire it to the PhidgetBridge 4-input.

Wiring Step 1:

Gather load cell wires towards on side of the scale and trim to the same length. Tape the bundle up to make this step easier.

Wiring Step 2:

Strip the wire ends and connect like-colors together. At this point you can either solder them together or use another method. I used insulated wire ferrules for this step.

Wiring Complete:

Now simply connect the wires to the PhidgetBridge and you are done!

Conclusion

This is just one way to make a scale using Phidgets. There are many different options available to you in terms of weight capacity, building materials, and number of load cells, just to name a few. If you have a cool scale you would like to share, let us know!