A PIN Pad Blasting UV Sanitizer

Retailers have instituted enhanced cleaning procedures in response to the COVID-19 pandemic, with an aim to keep frequently touched surfaces as clean as possible. Certainly one of the most commonly handled objects in the entire store is the payment terminal by the register, and the PIN pad specifically. Which is why [Josh Starnes] is working on a UV sterilizer that mounts onto a standard credit card terminal.

It’s a simple enough idea, but as is often the case, figuring out how to properly execute it is where things get tricky. [Josh] has already moved through several design iterations for his 3D printed enclosure in an attempt to make something that’s unobtrusive enough to be practical. The goal is to make something that the user won’t mistake for some kind of skimming device, which can certainly be tricky.

The skeptics in the audience will be happy to hear that [Josh] isn’t bothering with an LED UV source, either. We’ve all seen the pitfalls of trying to sanitize using UV LEDs, so this design goes old school with a small 12 volt UV bulb. That does mean it will need a dedicated power source however, which it seems like he’ll be addressing in the next phase of the project.


47 thoughts on “A PIN Pad Blasting UV Sanitizer

        1. Leave the alcohol in the beer! Unless it’s isopropanol, then don’t put it in beer…

          Nearly ruined a Swiss army knife earlier by cleaning it with isopropanol. Seems it can dissolve components out of plastics. Looked a bit dry for a while so wiped with mineral oil. Good for the mechanical parts and seems to have returned the sheen.

          It’s quite challenging to match chemical comparability. And since UV won’t go in the cracks, perhaps the best option is to heat all key pads up to 70°C. Still possible to touch for a moment, but the virus probably won’t like it.

    1. First thing I thought. I don’t know how it is in different areas of the world, but in western Europe, no modifications to the terminals are allowed. Banks will block your terminal and all bank accounts that used it when they find out. At the same time, smart customers will refuse to use it. Not strange, since this mod could easily house a camera to pick up your pincode.

      Even with our current (predominantly safe) EMV / contactless systems, eyeing a pincode and stealing your card is a real danger.

  1. Maybe this pandemic is what moves America to get rid of these types of pads in the first place. In Europe last year in several countries I never had to do anything other than tap my phone. I can tap my phone at my local grocery store and coffee house, but they still require me to either sign on a pad or enter my PIN. Which renders the whole thing useless. Time for a better experience.

    1. Contactless debit/credit cards still require you to enter a PIN every n-purchases to verify that it’s still you.

      Paying by phone works through Google Pay, so that’s not an option for anyone who values their privacy.

      1. I have two Bank of America Visa cards with both chip and mag stripe (but no NFC contactless). For purchases using the chip I have never had to enter a PIN, no matter what the purchase price is. I don’t know about purchases with the mag stripe though, it has never happened (yet). For any sort of ATM transactions, I have to enter a PIN every time. So if PIN-less purchases are OK with the chip, why wouldn’t PIN-less contactless purchases be OK too? Hmmm… Maybe it’s dependent on a particular bank’s policy (in the U.S. anyway).

        1. No PIN and no payment limit sounds like asking for trouble – or there’s a waiver in the contract that says, “If you lose this card, we take no responsibility whatsoever. You lose your money.”

          1. Well, most cards allow using them online with a high limit, by knowning just the numbers printed on the card – though some banks now have an extra mobile verification step.

        1. Your bank knows of it naturally, that’s part of the deal, but when Google starts recommending me liquor stores and strip clubs based on my shopping behavior, that’s where I draw the line.

  2. I was just about to place a project on my hackaday.io page with the DIY prototype of the non-touch keyboard, with IR active pairs emitter-phototransistor (4 for rows, and 4 for columns). There will be LED matrix with “press acknowledge” under the active IR plane (directed, so that only the user can see it), and a small speaker with a single “click”.

  3. If this works- it’s useful. Some of us have no way around using these damn TouchPads. He stands to make millions if this works and can be widely adapted in an accepted way.

    In a busy grocery store, it’s kind of impossible to avoid using these right after someone else. It’s got to be thd highest focal point of disease spread in modern society. Anything that people can do to disinfect these is useful.

    Personally, best method I’ve seen is plastic covers over keypad and sanitized wipe of it after each customer.

    1. It may be the highest focal point of disease, but that’s probably not saying much since most viruses that people talk about are respiratory, food poisoning, or STDs.

      It might be useful, if there’s no possible beam paths outside the keypad, and there’s a really good sensor to make sure nobody gets their fingers in the UV.

      Seems like FDA approved should be required for something that can exposed the general public.

    2. Contactless payments (at least here) don’t require you to touch the terminal under a certain amount. But even if you do, the virus won’t have any way to infect you while it’s on your hands. Just sanitize them when leaving the store (Something you should be doing anyway because you’re touching a lot of surfaces in the store) and you’ll be fine.

    1. Better question: is there any proof that there is any significant germ transmission through PIN pads?

      Yes, there’s plenty of anecdotal ‘evidence’ and lots of impressive rigged demos with fluorescent dye and even petri dish cultures, but I am not aware of a single case with unequivocal evidence of germ transmission through a keypad.

      In other words: is this even addressing a real need or relevant problem? Unless the problem is “Vendors need to be seen to be doing something about germs, and I need cash, so I’ll build and sell this nifty anti-germ widget and market it with all the FUD I can muster”.

    2. UV-C can breakdown organic matter on the surfaces of objects.

      UV-C is from 280nm to 100nm, so in theory it could break any bonds with bond energies from about 427 to 1200 kJ/mol.
      But the reality is that for a typical quartz mercury UV-C lamp there are two main peaks in the UV-C range.
      It has a one peak from 200nm (600kJ/mol) to 160nm (750kJ/mol) with a maximum near 183 nm (655 kJ/mol) and a larger second peak from 260 nm (462kJ/mol) to 230nm (521kJ/mol) peaking near 252 nm (476kJ/mol).

      So any bonds at that bond energy can be broken,
      C=C 602 kJ/mol (198.7 nm)
      C=N 615 kJ/mol (194.5 nm)
      O=O 494 kJ/mol (242.2 nm)

      So with a quartz mercury UV-C lamp, the lower energy peak (252nm) mostly generates Ozone and the higher energy peak (182nm) mostly breaks down organic molecules.

      The four most common elements in living organisms are carbon, hydrogen, oxygen, and nitrogen. So most organic matter have a double carbon bond or a double carbon nitrogen bond, including most hydrocarbon based plastics.

      Lucky for us no UV-C from the sun reaches the surface of earth, if it did no organic life could exist.

      A far safer option would be to replace plastic buttons with copper. Amazingly within minutes all bacteria or virus are dead, copper disinfects by being there. (ref: https://mbio.asm.org/content/mbio/6/6/e01697-15.full.pdf ) Contrast that with Teflon, PVC, ceramics, glass, silicon rubber, stainless steel which could be infectious for at least 5 days.

      1. But relatively pure copper oxidizes easily, the resulting patina reduces copper’s efficacy as a surface disinfectant. Are there copper alloys that resist oxidation but remain effective as a disinfectant? How long does it take to kill how many particles of various types? This is starting to sound like a deep rabbit-hole kinda’ thing…

      2. The real question is whether there are any germs on the pin pad in the first place.

        Washing your hands is important because it’s something we can pretty much totally control, which is easier than keeping the air totally clean.

        But it’s also provide not the main way this stuff spreads. What we need is to keep the air clean. By not going out in crowds. And when we do go out, by wearing masks.

        Cheap positive pressure HEPA masks for all would seem to be the real answer here.

  4. Better to just use cash really, that way you aren’t reliant on visa or mastercard as intermediaries, there is no risk of crooked authorities tracking and blocking your transactions (say for purposes of ratioing how many “unhealthy” foods you can buy per week), and by using cash you ensure you are able to still get things you need if the internet infrastructure on which card transactions rely gets temporarily cut off (the least sinister and perhaps most likely example of this is workers digging a new drain put the digger’s shovl through an optic fibre by accient). Cash is pretty safe from a germ perspective, in any given period of several days a given coin or note will have only been handled briefly by a small numebr of people, spending long periods inbetween sitting in a wallet or till.

    Might make more sense to design a steriliser to attach to a door handle and have it work out when the door has just been used and no humans are still in line-of-sight and give a good blast of the UV at that moment, if you fear surface transmission of viruses or bacteria then door handles should worry you a lot mroe than cash.

    1. I suspect cash would be more dangerous, because it takes more time, during which someone can cough on people, whereas surface transmission is probably not that relevant.

      Especially if you sanitize after leaving the store, which most people who care about surface transmission almost certainly are doing.

      Besides, I remember hating paying with cash back when it was a thing, counting and putting away change, having extra stuff to keep track of,
      not having any electronic logs to see what I spent that month without digging through receipts.

      Cashless payments are pretty much the obvious choice for anyone but serious privacy-interested people.

      1. The things you list were the best things about cash money:

        1) Not having to log online to see how much money you’ve spent – just withdraw the amount you intend to spend the next a week, and then what you have in your wallet is what you get to spend. If you happen to need more, there’s the ATM, but you really should have planned ahead anyhow.

        2) You automatically save money by dropping your change in a jar. It’s like tipping yourself.

        The reason I went cashless is because banks started demanding ridiculous fees for withdrawing and depositing cash, and they reduced the number of places where you can do it, and they started treating you like a criminal if you had more than your kids’ piggy bank money on you.

    2. ” there is no risk of crooked authorities tracking and blocking your transactions (say for purposes of ratioing how many “unhealthy” foods you can buy per week),”


      I really, really wish the comments section of HaD had an entry barrier.

      1. Health insurance companies are doing almost exactly this. They use your supermarket loyalty card to see how much booze/donuts/fast food you buy, and jack up your premiums, or scrutinise claims more closely.

    1. A petrol station nearby had Cling film placed between the cashier and the customer as a barrier – A lot cheaper than what is been charged for the perspex screens –

      Here we are largely contactless payment no pin required used to be up to $100AUD but I believe that has recently been raised

  5. Ingenico also makes an anti microbial pin pad that has copper impregnated paint. Also, even if the thing doesn’t look like a skimmer, it still opens up a physical vulnerability to install a skimmer (i.e. a camera that captures the users PIN with a convenient light for consistent video quality).

  6. Supposedly the soviets used a pencil in space instead of a pen that wouldn’t work in zero-G. NASA picked up a space pen for $$$. Seems like it’s time to get that rubber tipped writing instrument out again. Some of those keypads are hooded and hard to operate anyway.

    1. A pencil in a spacecraft is a bad idea. Graphite dust is conductive as well as flammable. Not to mention, graphite dust can cause irritation to the eyes. Also, pencils tend to break, causing even more mayhem. No, neither nation liked the idea of having pencils in space. But both actually did it. Until a private company developed a pen that could be used in microgravity / without gravity. Both NASA as well as the USSR quickly became big customers.

  7. Actually, the first question should be “does it work?” i.e. to kill viruses on surfaces. Not calculating theoretical UV energies on molecular bonds. DIY “sterilizers” need to be proven effective as the medical devices they purports to be: real viruses have to be placed on surfaces in calibrated amounts, exposed to the light and then assayed or cultured to see if the viruses are destroyed and not infectious. Otherwise you have no idea if it is at all effective in practice.

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