We’re all hopefully a little more concerned about health these days, but with that concern comes a growing demand for products like hand sanitizer, disinfectant, and masks. Some masks are supposed to be single-use only, but with the shortage [Bob] thought it would be good if there were a way to sanitize things like masks without ruining them. He was able to modify a microwave oven to do just that.
His microwave doesn’t have a magnetron anymore, which is the part that actually produces the microwaves for cooking. In its place is an ultraviolet light which has been shown to be effective at neutralizing viruses. The mask is simply placed in the microwave and sterilized with the light. He did have to make some other modifications as well since the magnetron isn’t always powered up when cooking, so instead he wired the light into the circuit for the turntable so that it’s always powered on.
Since UV can be harmful, placing it in the microwave’s enclosure like this certainly limits risks. However, we’d like to point out that the mesh on the microwave door is specifically designed to block microwaves rather than light of any kind, and that you probably shouldn’t put your face up to the door while this thing is operating. Some other similar builds have addressed this issue. Still, it’s a great way to get some extra use out of your PPE.
What do you do when you have to disinfect an entire warehouse? You could send a group of people through the place with UV-C lamps, but that would take a long time as said humans cannot be in the same area as the UV-C radiation, as much as they may like the smell of BBQ chicken. Constantly repositioning the lamps or installing countless lamps would get in the way during normal operation. The answer is to strap UV-C lights to a robot according to MIT’s CSAIL, and have it ride around the space.
As can be seen in the video (also embedded after the break), a CSAIL group has been working with telepresence robotics company Ava Robotics and the Greater Boston Food Bank (GBFB). Their goal was to create a robotic system that could autonomously disinfect a GBFB warehouse using UV-C without exposing any humans to the harmful radiation. While the robotics can be controlled remotely, they can also map the space and navigate between waypoints.
While testing the system, the team used a UV-C dosimeter to confirm the effectiveness of this setup. With the robot driving along at a leisurely 0.22 miles per hour (~0.35 kilometer per hour), it was able to cover approximately 4,000 square feet (~372 square meter) in about half an hour. They estimated that about 90% of viruses like SARS-CoV-2 could be neutralized this way.
During trial runs, they discovered the need to have the robot adapt to the constantly changing layout of the warehouse, including which aisles require which UV-C depending on how full they are. Having multiple of these robots in the same space coordinate with each other would also be a useful feature addition.
Designed to be used once and then disposed of, personal protective equipment (PPE) such as N95 face masks proved to be in such short supply during the early days of the COVID-19 pandemic that getting a few extra uses out of them by sanitizing them after a shift seemed smart. And so we saw a bunch of designs for sanitizing chambers, mostly based on UV-C light and mostly, sad to say, somewhat dodgy looking. This UV-C disinfection chamber, though, looks like a much better bet.
The link above is to the final installment of a nine-part series by [Jim] from Grass Roots Engineering. The final article has links to all the earlier posts, which go back [Jim]’s early research on UV-C sanitization methods back in March. This led him to settle on an aquarium sanitizer as his UV-C source. A second-hand ultraviolet meter allowed him to quantify the lamp’s output and plan how best to use it, which he did using virtual models of various styles of masks. Knowing that getting light on every surface of the mask is important, he designed a mechanism to move the mask around inside a reflective chamber. The finished chamber, which can be seen in the video below, is 3D-printed and looks like it means business, with an interlock for safety and a Trinket for control.
We love the level of detail [Jim] put into these posts and the thoughtful engineering approach he took toward this project. And we appreciate his careful testing, too — after all, it wouldn’t do to use a germicidal lamp that actually doesn’t emit UV-C.
Editor’s Update: According to the schematic for this project, SST-10-UV-A130-F405-00 (PDF) LEDs are used which produce 405nm UV-A light. The manufacturer, Luminus, does not recommend that part for disinfection or sterilization. Luminus sells UV-C LEDs for that purpose, generating 275-285nm. After publication the part number used was changed to and American Opto L933-UV265-2-20 which is a UV-C LED producing 265-278nm.
The global COVID-19 pandemic has had a serious impact on the hacking and making scene, though it hasn’t been all bad. Sure, shipping on average is taking a lot longer than we’d like when ordering parts, but otherwise being stuck at home has given many people far more time to work on their projects than they would have had otherwise. In some cases, it’s also been a reminder of just how far we’ve come in terms of what the dedicated individual is capable of producing within the confines of their own home.
As a perfect example, take a look at this UV sanitizer box built by [Md Raz]. Looking for a way to quickly and easily kill germs on smartphones and other small devices, he used the considerable capabilities afforded to the modern hacker to produce a professional-looking device in far less time than it would have if he had to outsource things like PCB manufacturing or injection molding.
Inside the 3D printed enclosure is an array of SMD UV-C LEDs that, according to the manufacturer’s specs, will destroy viruses and bacteria in 5 minutes. To make sure the LEDs are given enough time to do their job, [Md] is using an ATtiny85 to control the countdown and a seven segment display to let the user know how much longer they have to wait. All the electronics are held on PCBs produced with a BotFactory SV2 desktop PCB printer, but for those of us with somewhat more limited budgets, a mill or even a modified laser engraver could be used to produce similar boards.
Germicidal lamps are designed to destroy viruses and bacteria using ultraviolet light. But not just any UV light will work, and I came across an example of a lamp that was advertised as germicidal but a few things just weren’t right about it.
I ordered the UV-C germicidal LED lamp on Amazon, and received it a few days ago. It felt the suspicion from the first moment: playing around with a lot of different UV LEDs, I’ve learnt how the parasitic visible light from different UV ranges should look like to human eye. Also, proper UV-C LED lenses like the one shown here are made of quartz glass. Compare that to the image at the top of the article of the bulb I received that has a soft plastic lens, which is possibly opaque and degradable in the far UV range. The most important clue that something was wrong was the price. It’s hard to imagine that a UV-C LED lamp with the 253.7nm wavelength, made of more than 200 LEDs and in such a robust metal case, can cost only $62.99.
Although there was the risk of being unjust, I decided to return the product. In my message I bluffed that I measured the spectra of the lamp with a spectral emission meter, and that its output was not in the UV-C range. The next day I received confirmation that the bluff paid off: the seller replied that they advertised the product according to information from the supplier, and that the incorrect information was caused by their lack of understanding of product information. They also attached the official datasheet with the measured wavelength: it was not 253.7 nm, as advertised, but with the peak at 394.3 nm, and the dominant wavelength at 413.9 nm. It was not in the far UV-C, but in the near UV-A range and not at all useful for destroying germs! The seller promised that the product would be removed from their store, and kept the promise.
If you are thinking about buying a UV-C LED lamp, maybe you should get the good old CFL germicidal lamp. I don’t think that viruses care too much about the new technology.
The current situation has given closet germaphobes the world over a chance to get out there and clean the hell out of everything. Some of it may be overdone; we ourselves can cop to a certain excess as we wipe down cans and boxes when returning from a run to the grocery store. But sometimes disinfection is clearly indicated, and having an easy way to kill the bugs on things like face masks can make a big difference by extending the life of something that would normally be disposable. That’s where this quick and easy UV-C germicidal cabinet really shines.
The idea behind [Deeplocal]’s “YouVee” is to be something that can be quickly cobbled together from parts that can be picked up at any big-box home store, thereby limiting the number of trips out. You might even have everything needed already, which would make this a super simple build. The business end is a UV-C germicidal fluorescent lamp, of the kind used in clarifiers for backyard ponds. A fluorescent droplight is modified to accept the lamp by snipping off a bit of plastic, and the lamp is attached to the inside of the lid of a sturdy black plastic tote. The interior of the tote is lined with aluminum tape and a stand for items to be disinfected is made from a paint roller screen. The clever bit is the safety interlock; to prevent exposure to UV, the lamp needs to be unplugged before removing the lid. Check out the full build tutorial for details.
Looking to sterilize something? Give it a good blast of the old UV-C. Ultraviolet radiation in the shortest wavelength band breaks down DNA and RNA, so it’s a great way to kill off any nasties that are lurking. But how much UV-C are you using? [Akiba] at Hackerfarm has come up with the NukeMeter, a meter that measures the output of their UV-C sterilizer the NukeBox. It is built around a $2.50 sensor and a $3 Arduino.