Description:
A simple flex sensor 2.2" in length. As the sensor is flexed, the resistance across the sensor increases. Patented technology by Spectra Symbol - they claim these sensors were used in the original Nintendo Power Glove. I love the Nintendo Power Glove. It’s so bad!
The resistance of the flex sensor changes when the metal pads are on the outside of the bend (text on inside of bend).Connector is 0.1" spaced and bread board friendly. Check datasheet for full Specifications.
Note: Please refrain from flexing or straining this sensor at the base. The usable range of the sensor can be flexed without a problem, but care should be taken to minimize flexing outside of the usable range. For best results, securely mount the base and bottom portion and only allow the actual flex sensor to flex.
Description: A simple flex sensor 4.5" in
length. As the sensor is flexed, the resistance across the sensor
increases. Patented technology by Spectra Symbol - they claim these
sensors were used in the original Nintendo Power Glove. I love the Nintendo Power Glove. It’s so bad!The resistance of the flex sensor changes when the metal pads are on the outside of the bend (text on inside of bend).
Connector is 0.1" spaced and bread board friendly. Check datasheet for full
Features
- Angle Displacement Measurement
Mechanical Specifications
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Electrical Specifications
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-Life Cycle: >1
million
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-Flat Resistance:
10K Ohms
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-Height:
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0.43mm
(0.017")
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-Resistance
Tolerance: ±30%
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-Temperature Range:
-35°C to +80°C
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-Bend Resistance
Range: 60K to 110K Ohms
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-Power Rating :
0.50 Watts continuous. 1 Watt
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Peak
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"The
impedance buffer in the [Basic Flex Sensor Circuit] (above) is a single sided
operational amplifier, used with these sensors because the low bias current of
the op amp reduces errer due to source impedance of the flex sensor as voltage
divider. Suggested op amps are the LM358 or LM324."
"You
can also test your flex sensor using the simplest circut, and skip the op
amp."
"Adjustable Buffer - a
potentiometer can be added to the circuit to adjust the sensitivity
range."
"Variable Deflection Threshold Switch - an
op amp is used and outputs either high or low depending on the voltage
of the inverting input. In this way you can use the flex sensor as a switch
without going through a microcontroller."
"Resistance to Voltage Converter - use
the sensor as the input of a resistance to voltage converter using a
dual sided supply op-amp. A negative reference voltage will give a positive
output. Should be used in situations when you want output at a low degree of
bending."
Sensing A Bend With A Flex Sensor + Arduino
We spend so much time talking about sensing things less mechanical, that is is easy to forget the accelerometer isnt the only part in town. The flex sensor is one of those parts often overlooked by the advanced user. But what if you need to check if something bent? Like a finger, or a doll arm. (A lot of toy prototypes seem to have this need).
Anytime you need to detect a flex, or bend, a flex sensor is probably the part for you. They come in a few different sizes ( small, large).The flex sensor is basically a variable resistor that reacts to bends. Unbent it measures about 22KΩ, to 40KΩ when bend 180º. Note that the bend is only detected in one direction and the reading can be a bit shaky, so you will have best results detecting changes of at least 10º.
Also, make sure you don’t bend the sensor at the base as it wont register as a change, and could break the leads. I always tape some thick board to the base of it to make it wont bend there.
Hooking it up, and why
The flex sensor changes its resistance when flexed so we can measure that change using one of the Arduino’s analog pins. But to do that we need a fixed resistor (not changing) that we can use for that comparison (We are using a 22K resistor). This is called a voltage divider and divides the 5v between the flex sensor and the resistor.The analog read on your arduino is basically a voltage meter. at 5V (its max) it would read 1023, and at 0v it read 0. So we can measure how much voltage is on the flex sensor using the analogRead and we have our reading.
The amount of that 5V that each part gets is proportional to its resistance. So if the the flex sensor and the resistor have the same resistance, the 5V is split evenly (2.5V) to each part. (analog reading of 512)
Just pretend that the the sensor was reading only 1.1K of resistance, the 22K resistor is going to soak up 20 times as much of that 5V. So the flex sensor would only get .23V. (analog reading of 46)
And if we roll the flex sensor around a tibe, the flex sensor may be 40K or resistance, so the flex sensor will soak up 1.8 times as much of that 5V as the 22K resistor. So the flex sensor would get 3V. (analog reading of 614)
Code
The arduino code for this just could not be easier. We are adding some serial prints and delays to it just so you can easily see the readings, but they dont need to be there if you dont need them.In my tests I was getting a reading on the arduino between 512, and 614. So the range isnt the best. But using the map() function, you can convert that to a larger range.
int flexSensorPin = A0; //analog pin 0 void setup(){ Serial.begin(9600); } void loop(){ int flexSensorReading = analogRead(flexSensorPin); Serial.println(flexSensorReading); //In my tests I was getting a reading on the arduino between 512, and 614. //Using map(), you can convert that to a larger range like 0-100. int flex0to100 = map(flexSensorReading, 512, 614, 0, 100); Serial.println(flex0to100); delay(250); //just here to slow down the output for easier reading }
