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