Educational Force Sensor + Lab Exercises

thingiverse

3D printers are becoming more prevalent in schools these days, but what kinds of education specific things can they be used for? Why not an introductory lesson in physics?!! This is a functioning 3D printed load cell model capable of measuring force in tension and compression. You can change out the spring to measure forces up to 20 lbs! Links to the purchased parts and lessons explaining the science behind it are all provided in this Thingiverse post! This hands-on project is safe for kids and the result is durable and can be used for future educational experiments! Video Demo Here:https://www.youtube.com/watch?v=wAwtl4TtXP8 Update: Links to the non-printed parts for quick reference here:Hardware: (1) Spring (Spring-rate = 5.1 lb/in): http://www.mcmaster.com/#9657K428 (1) Alternate Spring (Rate = 3.77 lb/in): http://www.mcmaster.com/#9657K115 (1) Alternate Spring (Rate = 10 lb/in): http://www.mcmaster.com/#9657K429 (1) Sliding Potentiometer (2.36 inch travel): https://www.sparkfun.com/products/9119 (1) 1/4"-20 nut (1) 1/4"-20 hex bolt, 4" long, PARTIALLY threaded (not fully threaded) Data Acquisition: (1) Arduino Uno (Program in the ThingFiles) http://amzn.to/1XrtSUa (1) Screen Interface (this is optional because you can just use the Arduino serial monitor on the computer to read measurements. The buttons are overkill for this project but they are nice to have for other things.) http://amzn.to/2b47mQ8 Print Settings Printer Brand: RepRap Printer: Printrbot Rafts: Doesn't Matter Supports: No Resolution: .3 Infill: 15% Minimum Notes: Any material will work! Post-Printing Deburr all printed parts Just be sure to remove all traces of printing support/raft/scaffold/brim etc because these parts snap fit and slide together. How I Designed This Measure, Model, Print! First I designed the basic functioning device with a pencil and paper. Then I purchased all the non-printed hardware I knew I would need. Then I used digital calipers to measure the part dimensions and make 3d models of the fasteners, spring, and potientometer. Then I modeled the printable parts to match my concept drawings. When doing this I always try to minimize overhanging edges and ultrafine features that make 3d printing difficult. After I printed the parts I cleaned them up and test fit everything together. If the sliding connections were too tight or the press fit connections were too lose I would go back and adjust the model and reprint it to test it out again. (Oh yea, I used #CubifyDesign for my 3d models) Educational Force Sensor Lessons 3D Printed Force Sensor for the Classroom This is a partially 3d printed spring based force measuring tool. Overview & Background: In this Thingiverse Project I'm going to show you how to build a functioning 3D printed load cell model capable of measuring force in tension & compression. This project will give students a hands-on focus and a segway for more technical scientific discussions. Objectives: Using this printed force sensor students can learn: 1.How it Works (Hooke's Law) 2.How this compares to a professional load cell. 3.How do we even define what a pound is? (Calibration) 4.Digital electronic measurements: Bit Resolution & Proportional Scaling. Audiences: This tool is intended as tool for use in a science (physics) lesson/class. The intended audience for the full lessons are middle school through high school students, although the finished tool/toy itself can be enjoyed by all ages. Subjects: Physics, Math, Science, Computers/electronics Skills Learned (Standards): Hooke's Law & how to determine the spring rate of an unknown spring. Wiring up a potentiometer. Wiring up & programming Arduino. Lesson/Activity: Lessons take the form of guided discussion and experimentation with the device, intended in a specific order. (The complexity increases as you go!) Please refer to the ThingFiles download section for PDF files. Here are the steps for reference: Step1_PrintableParts&_BOM Step2_Assemble_The_Parts Step3_Wire_It_Up_and_Play! Step4_Discuss_How_It_Works+Mystery_Spring_Exercise Step5_Comparison_to_Real_Load_Cell Step6_Perform_A_Calibration (See MS Excel based Step6_Calibration_Calculator) Step7_Discuss_BitResolution&_Proportional_Scaling (See MS Excel based Step7_Printed_LoadCell_Calculations) Quiz_Loadcell_Lab Duration: Consider each step a 15 minute activity with the difficultly level increasing as you go. Although the explanation and discussion itself can last as long as the kids remain interested enough to ask questions! Preparation: It helps a lot to have assembled the parts at least once before you introduce them to the kids. (Just to make sure everything fits!) Then disassemble them before class so the kids can rebuild them to achieve the 'i-made-this' feeling. (If you have a late high school class then yuo can just let them 3d print the parts by themselves.) It also helps if the teacher is familiar enough with Arduino to be able to assist in uploading the program and perhaps editing a variable or 2. References The teachers will definitely want to read through the entire lesson before hand to make sure than they themselves understand what it is that they are sharing! Rubric & Assessment: Students should be able to answer all the questions on the quiz handout. They should be able to tell you what would happen if you were to do the following:Use a stronger or weaker springUse a longer or shorter potentiometerUse a different bit measurement system Also:What is Hookes LawHow do we define what a lb actually isHow to determine the spring rate of an unknown spring Handouts & Assets: See optional quiz handout. If the students are young then give them this at the beginning of class and have them turn it in after you perform the lab as a class or in small groups.