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Topic: How to choose the right resistor for the flex sensor (Read 53 times) previous topic - next topic

jack1992

Hello to everyone.I want to buy a flex sensor(4.5'') to experiment with it and i was wondering how to choose the right resistor.On the internet and the forums says that the 22K is good choice but it's my first time with flex so i need your opinion.Thanks in advnace.   

DrDiettrich

What's the purpose of the resistor?

If you need it to build a half-bridge, a first guess is the value of the sensor itself. If the sensor has very little resistance, chose a value that provides convenient current through the sensor, e.g. the suggested 22k. If then the signal range is too small, a full (Wheatstone) bridge and an opamp can be used to amplify the signal.

jack1992

What's the purpose of the resistor?

If you need it to build a half-bridge, a first guess is the value of the sensor itself. If the sensor has very little resistance, chose a value that provides convenient current through the sensor, e.g. the suggested 22k. If then the signal range is too small, a full (Wheatstone) bridge and an opamp can be used to amplify the signal.
I want to build this:
http://www.instructables.com/id/DIY-Robotic-Hand-Controlled-by-a-Glove-and-Arduino/

on the step 3 of the instructable says to use 22K resistor.I am confused.Every flex sensor can handle 22K resistor?

on this page says(https://www.adafruit.com/product/182)
 If they're unflexed, the resistance is about ~10KΩ. When flexed all the way the resistance rises to ~20KΩ.

on this page says(https://learn.sparkfun.com/tutorials/flex-sensor-hookup-guide)
This circuit requires one resistor. Many values from 10KΩ to 100KΩ will work.

so according to sparkfun 22K will do, right?Thank you for your time


DrDiettrich

When you study Ohm's law, you can calculate yourself how much the voltage on the center tap of a half-bridge will change, when your sensor varies its resistance between 10k and 20k, depending on the dummy resistor. Give it a try, you'll need it every now and then.

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