Automating Hand Sanitizer — If You Can Find Any

We once saw a Romeo and Juliet production where the two families were modern-day mob families with 3-piece suits and pistols. If they made King Richard III set in this week, the famous line might be: “Hand sanitizer, hand sanitizer, my kingdom for hand sanitizer!” Even if you have a supply stashed in your prepper cache, you have to touch the bottle so you could cross-contaminate with other users. Public places often have automatic dispensers to combat this, and now you can too. [Just Barran] shows the device in a video, you can see below.

Sourcing parts for projects is sometimes a problem, but right now we are betting the hand sanitizer will be the hardest component. Of course, the Internet is ripe with homemade brews that may or may not be effective based on beer, grain alcohol, or a variety of other base materials.

[Barran] has a big junk box. so he snagged an Arduino and an ultrasonic sensor. The part that is a little tricky is pulling down the pump. The basic idea is to use a servo motor to pull some fishing line. To engage the bottle, there is a small bit of plastic from a notebook cover and the fishing line goes to both sides of it. One side of the fishing line is fixed and the other is what the servo pulls.

We might have used a solenoid to push the button, but we like the servo method for its simplicity. In the end, it does look like it works well. Changing the bottle out probably requires a little surgery since there is a screw holding the plastic bracket in and you might have to update the fishing line lengths. That might be an impediment for a commercial project, but for your own use, it doesn’t seem like it would be a problem.

Fishing line is more useful than you might think. We’ve even seen it used as belts in 3D printers.

31 thoughts on “Automating Hand Sanitizer — If You Can Find Any

  1. That “production” was a movie. I saw it in middle school, IIRC… oh, how my English teacher from back then (with whom I am still friends!) would love to hear that I still remember that… :D maybe I’ll call her tomorrow. Shout-out to Mrs McEvoy, retired now from Jordan-Matthews High School in Siler City, NC — you did a remarkable job, and I hope *all* your students, over your many years of service, really do understand that.

    For the tinfoil hat crowd: I don’t care. I have nothing of sufficient value to anyone else, that I need fear robbery/etc (nor, at present or for the foreseeable future, the ability to change that), and I have exactly zero skeletons in the closet. If you want to be unnoticed, be unremarkable. Works pretty well, actually…

    …oh, right, the movie. Here you go:

    1. Double down, sanitize the pump top while you use it. Use each hand to pump for the other, and for the second hand, “inadvertently” smear some gel all over the pump. Then the next person to pump it inevitably touches some hand sanitizer _first_, and then replenishes some of it, and so on… unless people were trying to pump hand sanitizer without getting hand sanitizer all over their hands. In that case the whole scheme falls down.

  2. Always good to also show the simple things for the folks that are just starting with this kind of stuff. Personally i would change the ultrasonic sensor for a Time of Flight sensor, because the beam is way more narrow, so less false positives. Also no constant ultrasonic noise in your kitchen, your cats or kids might appreciate that.

    1. I was playing with capacitance based touch sensor PCB from China. It was a bit too sensitive as it can sense my finger about 1″ away. With a large piece of copper tape on the pump acting, it would increase the distance. The chip performs its calibration on power up.

      The virus only survive for 3 hours on copper surfaces vs days on plastic.

      Like Luke said above, if you are scrubbing you hand anyway so it really doesn’t matter that you touched the pump. The only thing it does is controlling the amount of soap. I would worry more about the water tap.

  3. It is actually a good idea because you would keep tapping the tap with your virus infected hand for starter. I would never think that servo has that much torque alone to be able to pull down the button… Now I just have to build it to see it.

    1. Though it’s a nice build, soap and washing liquids are much more efficient against this type of virus. It is covered by a lipid shell. Once the shell breaks the virus becomes disfunctional. Alcohol can’t penetrate the lipid shell half as good as soap. As long as you’re using some lipid-busting substance (e.g. soap) you don’t have to clean the handle afterwards.

      As for other viruses without such a shell: Alcohol can be be effective on some of them, but not as much as you might expect. This hysteria about desinfection liquids is just ridiculous. Anyway, alcohol can be very effective against certain bacteria and funghi, so you’re not doing anything wrong by using desinfection. It’s just virtually useless against COVID.

      Please, use soap, and learn how to wash your hands properly.
      Keep bustin’.

      1. Ah, thanks for that, was wondering whether I ought to hide certain cleaners in favor of ones that actually spell out their germicidal properties, but it appears that the “grease busting power!” will be adequate.

  4. So the last few days town has been fucking mental by the way and it’s like living in some shitty apocalypse film produced by politicians. Finally I get home from that. I think, “ah! some relaxing Internet! My hobby, which I do to relax from all the stress of the world with”…

    I can imagine the SEO-drones of the world have cerebral backflipped into ecstatic feedback loops, but for actual human beings, please, could we drop it? Can we talk about something else? The grownup scientists are taking care of this utter bother. Can’t we carry on gluing flashing LEDs to lolly sticks? Please?

      1. Interesting.. I have been pondering to myself what it will be like after, if everyone will in general pretend like 2020 never happened, or will they be telling war-stories all the time, “There I was, on the couch for 3 weeks straight…”

  5. “If you can find any”

    Just make your own. My recipe:

    30ml 99.9% isopropanol, 10ml aloe gel, 2-3 drops sandalwood (or other) essential oil for scent. Stir it all together and put in an appropriate vessel. If your vessel is a sprayer, thin it out with a little more isopropanol.

    I’m willing to bet quite a few people in a crowd of DIYers has access to high-grade isopropanol for flux removal, parts cleaning, or even cleaning resin in the case of MSLA printers.

    I’ve started making (and handing out) to people like my FedEx/UPS drivers, family, friends, etc.

    1. I didn’t have any aloe gel, so I use the old dried up liquid soap that had been sitting in the refill bottle and thin it down with 90% Isopropyl alcohol. It is a bit runny as it is mostly alcohol, but still lather up and use as soap for washing my hands. Can’t be too safe.

      I think they have already added a small amount of oil in regular drug store iso alcohol as people don’t like to see their skin turning white. i also stock the 99% for cleaning to minimize that.

      Now that even the major brewery in my country is also churning up sanitizer, I’ll expect to see some of them in the store shelves soon after the medical facilities get theirs.

      1. I’ll have to try the soap thing out as a backup, thanks!

        The stuff in the drug store isopropyl (70%-ish) is usually propylene glycol and/or glycerin, so it’s already not far off from hand sanitizer.

        Stay safe!

          1. Though serious answer, I just realised I temporarily forgot about it because I haven’t seen it in 5 years or so. The green stuff usually has oil of wintergreen in it, which as you may guess is a little oily, so never use it for contact cleaner etc. There may have been some carcinogenic concerns. It was used as a sports muscle rub for relieving aches and pains, hence the term rubbing alcohol, of which the green wintergreen stuff is more rubbing-y than alcohol-y in terms of general purpose use. Will still kill germs though.

  6. Adjusting the line is only necessary if you swap the brand (bottle) of disinfectant. Dettol (automatic sanitizing soap dispenser) does of course the opposite: They created a special cartridge like interface and sell you slightly overprized bottles of soap which fit. But I am quite sure, I will be able to refill it when necessary. It does not seem to have a chip like a printer cartridge.

  7. Would be good to combine this with a timer. Most people don’t use enough hand sanitizer, and don’t leave it on the skin long enough. (Needs to be moist for 60 to 90 seconds.)

    I prefer to go for the soap, but if going to use sanitizer, at least make it effective.

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