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Topic: Best resolution with bend sensor and voltage divider? (Read 1 time) previous topic - next topic

mcsteeze

Hello,
I currently have a project with three bend / flex sensors. I believe the sensors put out 100kohm- 500kOhm depending on how they are bent.  From what I have read, I have to include a voltage divider in the circuit to read the values from the analog pin to which the bend sensor is connected (anyone know why?) I have wired in a 330kohm resistor as the voltage divider but my readings are not very good.  I am only able to get a range from about  .59-.70 (I read the values on a computer program so I am not sure what that translates to out of 1024. 
Any suggestions on what size resistor I should use (assuming that the bend sensors are indeed putting out 100-500kohms) Thank you

Grumpy_Mike

In general it should be the size of your average reading.
The sensor should be wired from input to ground and the resistor from input to +5V.
It sounds like you are using the right value but have wired it up wrong.

The resistor is needed to turn a varying resistance into a varying voltage, as you can't measure resistance only voltage.

mcsteeze

What's strange about this is that I am still getting readings (accurate ones) just not very detailed. Are you saying that even if I have it hooked up backwards (with the sensor reading going to the arduino pin and the resistor going to ground) I will still get some reading?  (Meaning I could improve the accuracy by switching where the resistor is in the circuit?

mcsteeze

Could you be a little more clear on how it is hooked up. You use the term input and I am not sure what you mean. This tutorial shows the fixed resistor going from the bend sensor to an analog pin to ground...and the bend sensor from 5v to the analog pin...Is this what you mean?

http://bildr.org/2012/11/flex-sensor-arduino/

Grumpy_Mike

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Meaning I could improve the accuracy by switching where the resistor is in the circuit?

No you just switch what directions the readings go when the bending happens.

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This tutorial shows the fixed resistor going from the bend sensor to an analog pin to ground...and the bend sensor from 5v to the analog pin...Is this what you mean?

Yes that sort of thing although as I said I would swap the resistor and sensor in that circuit, just a personal preference it won't change the rang of reading you get.

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