Step 12: Circuits

Picture of Circuits
Flex Sensor Circuit V2 - Linear - Schematic.bmp
If you've gotten to this point, your Soft-Circuit position sensing glove is in working order so now the fun can begin!

Flex sensors only change resistance with respects to bend angle. You're going to have to build a circuit to convert this resistance change into a voltage to make it useful.

Here is the Spectra Symbol Flex Sensor spec sheet. They describe a couple different circuits you can use for different applications. Basically, the simplest one is to use it as a variable resistor in a voltage divider (with an op amp impedance buffer tagged on at the end of it). 

We design our circuits and protoboards in Eagle. This is a great way to plan out your circuit elements' positions before hand. We've posted pictures of the Eagle schematic and board layout files below. (The pictures look pretty small but if you click the "i" button when you hover over the image, you'll go to another page where you can download the much larger original images.)

Note: The circuit we built for the demo is for applications where you want to monitor the angle of bend of each finger. However, the circuit you need will change depending on your intended application for the glove. Some examples of circuits for other applications can be found in the Spectra Symbol datasheet as well.

Basically the circuit works like this.
5V input voltage --> inverting amplifier with a gain of -1 ----> voltage divider ---> inverting amplifier with a gain of -2.5 ---> MCU analog input pins.

Well eventually get around to posting an instructable detailing how to build the one we used in the demo. Until then, feel free to ask questions.
mina_dm2 years ago
Hello, this is very interesting and innovative. Please if it isn't too much trouble, do you mind explaining the circuit in the pcb design above. I am just a beginner in electronics and I would like to understand it better. I hope to hear back soon.
KcPower4 years ago
Hey! Nice instructable!! Is there a way to use it to control my HI-FI system?
jeff-o4 years ago
Will you be making an instructable detailing the interface circuit, too?