DIY a low-cost FLEX sensor

Hello everyone, in this tutorial you will learn how to make a FLEX sensor at home for next to nothing. The cost of this type of sensor in the market is very high, ranging from 60 to 200 yuan.

They are useful on an industry level, but the cost is too high for making DIY technology projects at home. Therefore, I bring you alternative solutions for sensors and I will show you how to easily build one at home.

Step 1: Story, Research and Work

1.1 Bending sensor

A bend sensor or bend sensor is a sensor that measures the amount of deflection or bending. It is also known as flexible potentiometer. It works on the principle of resistance and gives various values ​​based on the change in resistance.

Its working is very simple. Since the distance between the conductive particles present in the sensor is very short, it has low resistance when held straight. As it bends, the distance between the particles increases, causing higher resistance and lower current flow through the sensor.

This way we can easily use a microcontroller board like Arduino because all we need to do is use the sensor as input and we will get a value between 0 and 1023 where 0 means straight and 1023 means curved .

For more information about flex sensors read this pdf from SparkFun Electronics!

1.2 Intrusion sensor:

Now what we're going to do here is we're going to replace the resistive carbon element inside with pencil completely masked paper. Pencil lead conducts electricity and we will use this to our advantage.

For the main conductive plate of the sensor we will use two strips of tinfoil/aluminum foil as they conduct electricity very well and again we will use these easy to use materials that can be found in every home which will work to our advantage.

The sensor will have two terminals and we can easily connect it to the Arduino board. Flexible sensors have a wide range of applications:

car control

medical equipment

industrial control

Computer Peripherals

fitness products

musical instrument

measuring equipment

virtual reality games

consumer products

Physical therapy etc.

It's all about a simple flexible sensor and how we can hack the sensor to fit our needs and drastically reduce the cost using easily accessible and low cost materials!

Now, let's go ahead and gather the materials we need and actually start building it!

Step 2: Gather what you need

2.1 Required materials:

2 x cardboard strips (10cm x 1.5cm)

1 x paper strip (10cm x 1.5cm)

2 x tinfoil/aluminum foil strips (9cm x 1cm)

some glue

pencil

2 x small jumper wires

2.2 Tools (optional):

hot glue gun

Collect the items above and proceed to the next step!

Step 3: Glue the tinfoil strip to the cardboard strip

This is a very simple step. All you need to do here is glue the two strips of tinfoil to the two strips of cardboard you cut earlier. You can use any type of glue to adhere the tinfoil strips to the cardboard strips.

Make sure the tinfoil strip is centered relative to the cardboard strip and does not extend past the edge of the strip. There's a very important reason for this, as you'll see later!

You can even use the image above to follow along. Now move on to the next step!

Step 4: Color the Strips

This step is also very easy. The reason I repeat this statement is that this project is really easy to make and anyone can complete it without any technical experience. Now coming to this step, we just need to mask on both sides the strip of paper we took earlier. You can use any type of pencil.

Just make sure you shade the note very dark. I'm sure it'll be a mess after you're done printing with black carbon everywhere, but I guess that's okay :)

Without further ado, let’s move on!

Step 5: Connect wire ends to strips

Now what we need to do is we need to "create" sensor terminals using which the sensor will actually be able to interact with other electronic components. We only need two wires. I took two female jumper wires and cut them off near the bus connector so that later we could plug the two jumper wires into the sensor terminals.

You can also use any regular wire if you wish. Now we just need to glue these wire ends to each of the card foil strips we prepared earlier. You can use hot glue like I did, or you can use some tape to get the job done.

Just make sure you press the end of the wire onto the foil properly as it won't work properly without proper conduction.

Go to the next step!

Step 6: Stack Materials

Now we just need to put together the individual components we made earlier. Stacking will be in the following order:

any card chaff

shadow paper

any card chaff

However, make sure the card foil is facing inwards. Now just use some hot glue or tape to make sure the ends are connected so the sensors are securely held together and don't fall apart.

Step 7: Final Look

That's the process of building this DIY Flex Sensor. Make sure you bend it a few times when you're done making it and see if the hot glue stays where it should be, as sometimes it can happen that the hot glue can tear when you bend the sensor.

As you can see in the picture above, our sensor is very neat. If you have artistic talent, you can also customize and beautify it

Now it's time for the last part. test

Step 8: Build the Test Circuit

Now we need to test the sensor to see if it's actually worth making. We need an Arduino board and an LED to test our flex sensor. We also need a 22kΩ resistor. It will be better if we use a breadboard as this will make the circuit building process easy and fast.

I've attached all the necessary resources like schematics and code that will help you test your own flex sensor and see if it works.

Just follow the circuit diagram and use my code or write your own and hope it works.

Code:

Finally, if your sensor isn't working, try some of the following as troubleshooting measures:

Try using better quality tin foil

Make sure the wire ends are pressed firmly against the strips, you can even test them with a small conduction test.

Make sure the two foil strips are not touching each other.

Make sure you have penciled the paper very dark.