Conductive Rubber Cord Stretch Sensor + extras! Measuring stretch forces isn’t easy – unless you have some conductive rubber cord! This cord is 2mm diameter, and 1 meter long, made of carbon-black impregnated rubber. Usually this material is used for EMF gasketing, but its also very fun to play with.
In a ‘relaxed’ state, the resistance is about 350 ohms per inch. As you pull on it, the resistance increases (the particles get further apart). As you stretch it out, the resistance increases linearly. So lets say you have a 6″ piece – thats about 2.1 Kohms. Stretch it to 10″ long and now it is 10″/6″*2.1K = 3.5 Kohms. You can stretch the rubber about 50-70% longer than the resting length, so a 6″ piece shouldn’t be stretched more than 10″. Once the force is released, the rubber will shrink back, although its not very ‘fast’ and it takes a minute or two to revert to its original length.
This stuff is fun, so we give you a full meter and also two alligator clips (to connect to the cord) and a 10K resistor. Together, you can use these to make a simple voltage divider. Then use our handy Thermistor tutorial to measure the analog voltage and convert that back to resistance.
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, or even use Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for MakeCode, CircuitPython, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.