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  • Writer's pictureJon Peroutka

Custom RFID laundry scanner

Updated: Jul 6, 2023




Problem / Opportunity


Laundry is not my favorite activity. Fortunately for me, my amazing girlfriend has been gracious enough to take on the chore of our laundry (thanks hun!). While this has been super helpful, we ran into a bit of an issue. Many of my clothing articles don’t go into the dryer in order to avoid the items shrinking and no longer fitting. But by combining our laundry together and washing them together, some items which needed to be pulled out of the load before going into the dryer were missed amongst the other items which were meant to go into the dryer. These missed items went through the dryer cycle and ended up shrinking - and I couldn’t wear them anymore.


The simple solution would be to sort the laundry beforehand into the items which were meant for the dryer and items which were not. However, even with this process, there were still some items missed if I wasn’t careful about inspecting the laundry. So, I wanted a solution which would be able to scan a load of laundry which had both categories of items in it (dryer-friendly as well as dryer-unfriendly) and be able to tell the user if there were any dryer-unfriendly items in the laundry load, how many items, and what they looked like so that the user could find them more easily. Then the user/laundry washer could pull those items out of the load and ensure nothing inadvertently goes into the dryer.



Research


After looking on the internet for solutions which could fit my need, the closest ones I could find were commercial-grade RFID-based inventory management scanners. These are scanners which are meant for business such as hotels who wish to track their linen inventory. The idea is that each linen would have an RFID tag sewn into it, and the tag can be scanned to identify if it had been washed and with which products, as well as identify any theft which has taken place on their linens.

This was exactly the solution I needed. However, these devices were priced much higher than I thought was reasonable for my use case, around $1000 or more - yikes! I couldn’t find anything close to the price range which I wanted, so I decided to build my own.



Solutioning


I learned that I had to use an ultra high RFID protocol due to the distance which would be required for sensing RFID tags (1-3 feet). During my research, I came across an arduino-based, ultra high-frequency RFID reader shield (below). I kept this in my back pocket, and I eventually concluded that this was going to be my best bet for my solution.

I started by creating a rough “logical” sketch of what I thought the solution could look like, to gauge what I would need to buy, how much it would cost (knowing that there would likely be some variance once I started in the project), and what the 3D printer parts might look like. (did I mention this was rough?)



Parts and Prices:

  • UHF RFID Shield - $240

  • Arduino Uno - $20

  • Battery - $10

  • Screen - $15

  • Button(s) - $2

  • External Antenna - ~$30

  • 3D Printed Parts - ~$10

  • Miscellaneous Wires, screws, etc - ~$10

  • Laundry-friendly RFID tags - $1.25 per tag


Total cost would be around $330 (at least $600 less than purchasing an existing product), not including the cost of the tags.


Now, this was the first arduino project I had ever thought about building. I had never coded in C++ before, had no knowledge of the arduino ecosystem, and had extremely limited electronics engineering and 3D modeling experience. [sidenote: my dad is an electronics engineer, so I told myself that I would reach out to him if I encountered any blockers on that front. He was definitely a help for this. Thanks, Dad!]


I took some time to do some research on what arduino is, how to get started, how components get linked to each other, etc. I watched youtube videos, searched google, read articles, and finally read various forum threads on C++, existing arduino libraries I could use, and electronics engineering concepts. Eventually I got the feeling that I may be able to make this work, so I took the plunge and purchased all the components I needed.



Build


Once I received the parts, I started by confirming that the RFID shield connected to the Uno was working for me. I followed the sparkfun.com’s hookup guide instructions closely. I was able to confirm that the RFID reader was successfully reading the tags with the uno connected to the computer via the Universal Reader Assistant software found in the guide.


With that confirmed, I went on to confirm that I could read the RFID tags via the arduino serial monitor in the arduino IDE, utilizing some of the available libraries called out in the guide.





With that successfully built, I moved next to building the ability to display the RFID tag’s EPC (the tag’s unique ID) in the display.




With the screen working, I had the primary functionality successfully built. The next big hurdle to undertake was the 3D modeling. This was easily my most ambitious 3D modeling challenge to date. I broke up the whole design into 5 major components: the main bay which holds the uno & RFID shield, the screen compartment, the compartment for the battery, the lid to cover the battery, and the handle.


Below is the main bay I designed:










Next, was assembly and wiring.





Along the way, I wired up an on/off button, clear button (to clear the screen of scanned tags at the user's discretion), and the usb battery bank. I added an external antenna as it added considerable range and ensured the best detection rate. I also added a temperature/humidity sensor as I was concerned that heat and moisture from using the device inside a warm dryer could cause damage.



Final Product


At last, the final product!











Below is an example of an RFID tag affixed to one of my hoodies. It's a specific type of RFID tag intended for linens and has a soft cloth-like touch to it. With it affixed to the main tag on my clothes, it's soft enough to not be uncomfortable on my skin.





The solution has proven very helpful and eliminated all items from inadvertently going through the dryer cycle. It's been a great success and a fantastic learning experience. I very much enjoyed the project and had a great sense of accomplishment from it.



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