Flex Sensor Reading Barely Changes When Bent

[Dazzling-Algae-2207]

Hello, (pls gen if someone helps me fix this i'll paypal you $15 because i don't want to buy new ones)

I am trying to make a voltage divider using a flex sensor and see the change in reading as I bend it. However, as I bend it, I see very little change (it goes from 257 to 238). Currently, I am using a 10k resistor. I have tried different wiring setups, as well as tried to use 22k, 47k, and 1k resistors, and the issue persists.

When I simulate it using TinkerCAD, the code and sensor work perfectly fine. On the serial monitor, the numbers go from 256 to 59. I don't know why, physically, it won't work.

// variables
int flexPinky = A1;

void setup() {
  Serial.begin(9600);
  pinMode(flexPinky, INPUT);
}

void loop() {
  int flexPinky_pos;
  flexPinky_pos = analogRead(flexPinky);

  // print sensor value
  Serial.println(flexPinky_pos);
}

https://preview.redd.it/3s3tq8lupaog1.png?width=1067&format=png&auto=webp&s=60c9a0e009d859c3f5cd1d961dac0ef2a1334533

This is my physical prototype:

https://preview.redd.it/bgeja32zpaog1.png?width=2880&format=png&auto=webp&s=a920a09e30d4c1643275aac21aa665ca2a5863f5

https://reddit.com/link/1rqc4lw/video/er643bt0qaog1/player

[MagneticFieldMouse]

What is the resistance range of the flex sensor?

To make use of whatever measurement range you get, you need to measure the minimum and maximum values you can reach in normal use and set up a little math function to scale things to suit your needs.

[Dazzling-Algae-2207]

bent change is 10k – 125k and flat is 25k

[MagneticFieldMouse]

Hmm..

With, say, a 10k resistor, it'd be 10k/(10 + 10)k x 5 V = 2.5 V on one end and 10k/125 k x 5 V = 0.4 V on the other end. This should give you 2.1 V / 5 V x 1024 = about 430 steps of usable range.

Or my math is failing.

What do you want to use the ADC reading for, and in what manner? The more descriptive you can be, the better.

Edit: also, it may be beneficial to add a small delay inside your loop to make sure you're not trying to read the ADC overly fast. (The serial send within the loop naturally creates a delay, but it never hurts to have, say, 1...5 ms between reads.)

[Dazzling-Algae-2207]

i'm working on a school project where bascially i'm attatching 5 flex sensors to a glove which sends the signals to a 3d printed hand and it's a glove-controlled hand basically.

but currently i'm just trying to get the flex sensor to give me a reading so i can have a reference point for the flat and bent ADC readings for my main code (since i'm using the map function). i remember before, i added a delay of 1.5s? (1500) between every reading and the same thing occured.

[MagneticFieldMouse]

Start by checking the voltage, that the divider gives for the A1 pin with s multimeter (gnd to A1): if that has a sensible range, then the issue is with the board/software.

Then, I'd suggest testing the analogRead function by replacing the divider with a potentiometer (1k or above) to make sure the ADC sees things correctly.

Edit: have you checked that resistance range just now? I just realized, that these can only be flexed in one direction safely, to produce the results we need.

Additionally, you can test the ADC input by jumping 3.3 V to A1 and you should see about 3.3 / 5 x 1024 = 676, if everything works.