cheap smart rfid packet for moisture detection - super absorbent polymer powder
I'm sorry it was a rather lengthy guide, but it's such a simple concept that I really want to share with you guys and I hope you guys like it!
The purpose of this project is to design a cheap sensor package that can be used to identify the presence of water.
One of the ways to achieve this is to use any standard RFID tag, silver foil, high absorbent powder (
Similar to what was found in diapers)
And paper towels.
The frequency is very high for this project (HF)
RFID tags are used. The reason for the selection is that the frequency at which the hf rfid tag works is 13. 56MHz.
This is ideal for this project, as this wavelength is not affected at close range with water.
In this project, I also developed a way to easily show when tags are triggered and when Arduino, LCD screen and RTC modules are used.
For this project, you need-
USB-HF RFID Mifare card reader£14. 80-
RFID/NFC tags (
These can be any size or style for this item. 45mm round coil hf rfid tag used)~ £2 -£10-
Kitchen paper towels (
Any paper that will not completely dissolve once wet)-
There should be around the house-
Silver foil of any kind-
There should be around the house-
High absorbent diaper polymer (
This will be our absorbing material)-£19.
99 case used to identify when triggering smart RFID packets-
Tiny RTC I2C dscash-£1. 44-
LCD display 20x4 characters£3. 30-
ABS case 197x113x63mm-£5.
The cost of the whole project should be around £ 60, but the actual cost of smart RFID packets per packet can be only 50 p!
Now that all this is covered, let's get started!
So the theory behind these smart RFID packets is that silver foil will act as a ground plane.
This means that when the ground plane is close to the antenna of the RFID tag, this will interfere with its properties so that it cannot be transmitted normally (
There is a lot of math and theory behind this, but basically the closer the ground plane is to the RFID tag, the smaller the reading range of the tag)
There are three layers of smart RFID packets. The picture above explains how the packet works, while the packet dries the distance between the RFID tag and the silver foil (Ground plane)
Small, which means that the RFID reader will not be able to recognize the RFID tag when the packet gets wet. The suction powder will expand sharply, increasing the distance between the RFID tag and the silver foil (Ground plane)
Allows the tag to work properly and allows the RFID reader to identify the tag.
The chart above shows the distance between silver foil (Ground plane)
The RFID tag increases over time, and the RFID tag also reads the range until the distance is so large that the silver foil (Ground plane)
There is no longer any impact on the label.
For this project, I purchased 45mm HF RFID tags, and the reason for selecting the HF RFID tag is due to the functional frequency of the HF tag.
The function frequency is 13.
The 56 MHz signal is very close to the water and will hardly be disturbed.
Another benefit of this is that since most hf rfid readers share this band, they are also able to identify NFC tags.
It's easier for this intern to choose a label!
The first picture above shows the 45mm circular coil hf rfid tag I used in this project.
Using my RFID reader, the reading range of this tag itself is about 40mm.
The first step in making smart RFID packets is to pull out the required amount of paper towels, which will be used to keep the packets together.
The second and third pictures show me my bag organization shell.
The final smart RFID packet size is 50mm x 50mm.
Now that the smart RFID packet has a shell, you first want to put the RFID tag in the center position you see in the three images above.
The next step is to put a small amount of suction powder on the top of the RFID tag, I am trying to cover the entire RFID tag with enough money, which can be seen in figure 4 above.
I used the distance of 50mm x 50mm again for this project.
This silver foil is very important (Ground plane)
Is equal to or slightly larger than the size of the RFID tag antenna.
This can be shown in image 5 above and you want to place silver foil (Ground plane)
On top of the suction powder.
Now that all the layers are in place, you want to wrap the sides of the tissue around the top of the silver foil and then close the package with a small amount of taps.
My last packet can be seen in image 6 above, note that it is important to mark the side with an RFID tag as the top of the packet.
Now it's time for the packet to test it!
In testing this, I used a measuring spoon of 5 ml and I put the smart RFID packet on the card cell spacing (
Paper can also work)
This spacing is 3mm thick, ensuring that my reading range measurements are as accurate as possible.
I started with a spacer, meaning that the RFID tag was 3mm away from the reader and then added 5 ml of the water.
I use spacing to identify the maximum reading range of 5 ml of the water added to the packet, and then use 10 ml and so on until the packet is no longer extended.
The way I designed the packet I found that after adding 20 ml of the water, the packet stopped expanding, at which point the packet has expanded to about 10mm, as shown in figure 2 above.
The final result I read is related to ml water, as can be seen in the chart above, I did 10 tests with different packets and read the range on average per ml, to get the results shown in this table.
We can see that the reading range of smart RFID packets has never reached the maximum value of the RFID tag, due to the fact that the water is very close to the tag.
I found that the maximum reading range for a smart RFID packet is 28mm, and the maximum reading range for RFID tags alone is 40mm, which means that water reduces the maximum range by 12mm, this is reasonable for the functional frequency of the tag I chose.
I would really like to see what you have achieved with some of your packet design!
I know this is far from the best design, so please post what you found below if you try it yourself!
: D. since I purchased two different RFID readers, I would like to be able to identify when the RFID tag was found separately for each reader.
The first goal is to find a way to identify when tags are found on the RFID reader board, after a little testing, a finds out
Welding pin output, output 1 when the label is identified, I think this is used during board verification.
The first picture above shows the board of my RFID reader, the pin in the red circle is my RFID trigger pin.
With this, I can now design a circuit that uses Arduino to monitor each trigger of an RFID reader, and if one gets higher it updates the LCD time to indicate which reader is triggered, and view the real-time clock (RTC)
The time when the module prints the event.
The final circuit configuration can be seen in the second picture.
The software running on the Arduino can be described in the third picture of the system flow chart. The final Arduino code can be found once the code and circuit are fully tested. I designed a PCB to help clean up the terrible breadboard mess I was using.
Figure 4 shows the final breadboard design (
Yes, it could have been done smaller, but the size is not a real problem for the case I chose)
Now that the code and PCB are complete, it is time to measure the position of the LCD, LED RFID reader input and power supply.
Figure 1 above shows the size and position of all of these holes made using dremel.
After the hole was hit, I started installing the electronics, starting with the front assembly including the reset switch, LED and LCD display.
This can be seen in image 2 above.
Once these are installed, the RFID reader input is extended to the side of the shell that can also be seen in image 2 above.
Now, with the installation of all the key components, the Arduino is connected to the PCB and then installed behind all the front panel electronics seen in image 3, USB-
B. reach the cable of Arduino to eliminate the need for internal power supply.
Figure 4 shows the front of the housing after installing all components and tightening the housing.
Figure 5 above shows the final shell test that triggers two RFID tags, in short, it's a cool project involving electronics that I 've had little experience with before.
It's a simple and cool way to make a smart RFID packet with nothing but a standard RFID tag and other parts you might put in your home.
I hope you enjoyed this guide, please feel free to ask questions in the comments below!
Thanks for reading!