With all the hands-free dispenser designs cropping up out there, the maker world could potentially be headed for an Arduino shortage. We say that in jest, but it’s far too easy to use an Arduino to prototype a design and then just leave it there doing all the work, even if you know going in that it’s overkill.
[ASCAS] took up the challenge and built a cheap and simple dispenser that relies on recycled parts and essential electronics. It uses an IR proximity sensor module to detect dirty digits, and a small submersible pump to push isopropyl alcohol, sanitizer, or soap up to your hovering hand. The power comes from a sacrificial USB cable and is switched through a transistor, so it could be plugged into the wall or a portable power pack.
We admire the amount of reuse in this project, especially the nozzle-narrowing ballpoint pen piece. Be sure to check out the build video after the break.
Hopefully, you’re all still washing your hands for the prescribed 20 seconds. If you’re starting to slip, why not build a digital hourglass and watch the pixels disappear?
I got excited when I read that headline and got disappointed when I got to the bit about dirty digits – but I guess it could be adapted :-)
My thought’s exactly, anything over 140 proof (U.S. Proof) would be good for the hands and the mood.
The thought of DIY electronics suspended in flammable liquid is a little concerning.
Just remember, if something goes wrong you’re going to have to compete for attention at the Emergency Room with the COVID victims. Stay safe and choose low risk solutions for the time being. A peristaltic pump plus conformal coating on the electronics might be more sensible.
This is a good point. But i would be suprised if alcohol could catch fire with out oxygen being present (when the pump is submerged).
Any time the pump dispenses liquid, air must enter the bottle. Vapors can exit through the same hole.
The worst case scenario is that the circuit malfunctions and runs the pump until the container goes dry, then the motor (being a simple brushed motor) ignites the vapors and pops the top off. Then you have a desk full of fire.
These small pumps are usually quite water-tight and use brushless motors. The biggest flammability would be in gas phase, so for the peristaltic pump with brushed DC motor would probably be the most dangerous setup.
The fuel pump in my cars tank is brushed, and the fuel runs straight through the motor itself. Think about that.
And I seriously have to wonder if that cheap water pumps plastic housing and adhesives were designed with alcohol duty in mind, so “water-tight” is kind of moot.
And a peristaltic pump is meant to be outside of the reservoir, not immersed in it.
true, fuel pumps use the fuel as coolant in ‘older’ designs – that is one of the reasons not all can run on ethanol (it is conductive). i’m a bit concerned about over-spilling, maybe a very basic timer and a way to detect something doesn’t activate the pump accidentally.
No. Ethanol is not conductive.
Corrosive, not conductive. Well, it becomes conductive once it has dissolved bits of metal.
https://www.sciencedirect.com/science/article/pii/S0016236110005983
Ethanol is directly corrosive to aluminum.
But it’s also indirectly corrosive to other metals, because ethanol can absorb large amounts of water and create conditions for bacteria to survive in your fuel tank, where they create acetic acid by eating the ethanol. This happens particularly with low ethanol fuel blends with 5-15% ethanol, whereas high ethanol blends over 20% are too harsh for the bacteria to survive.
Have you opened one up? I would think they use very cheap brushed motors….
Considering the pump is less than $1 (I paid $0.86+shipping) , you won’t get anything fancy.
That particular pump used by OP uses brush motor and is not water tight. For this project, probably okay.
https://1.bp.blogspot.com/-sJTmqgivw2A/XnAFpwfaQEI/AAAAAAAADPU/hCfhuB2YgnAqkiZ8t5PfEVh2tz1Jnyp-gCLcBGAsYHQ/s640/IMG_2682.JPG
see the dark brownish motor vs OP. Mine has rust and the motor no longer works at the rated voltage. It needs 20V to break off the rust to start. Mine also had a leak on arrival that I seal up with superglue.
There are different types of pumps that do not submerge the motor, but this one was the cheapest. My replacements are probably stuck because of virus lock down.
author just squeezes z few cc of alcohol into the water. It is not pure and thus inflamable at room temperature. Also, as Mettor and jpa point out: you still need oxygen and a spark which are both absent.
A few CC is useless as you need at least 60% ABV (Alcohol By Volume) to kill this virus. 60+% is flammable.
FYI:
>The term proof dates back to 16th century England, when spirits were taxed at different rates depending on their alcohol content. Spirits were tested by soaking a pellet of gunpowder in them. If the gunpowder could still burn, the spirits were rated above proof and taxed at a higher rate.[1] As gunpowder would not burn if soaked in rum that contained less than 57.15% ABV, rum that contained this percentage of alcohol was defined as having 100 degrees proof.
Flammability depends on temperature. If you take a spoonful of 40% vodka and heat it up a little, it will ignite and burn until it’s just 10-15% ethanol left. Same goes with the proof test – you would get stronger spirits on a colder day.
Don’t have to heat it up if you’re not soaking gunpowder in it, I think you can light down to ~35% by itself and a few percent less with a wick. Well not heat above typical room temperature, if you keep in the fridge, you might have issues lighting off stronger stuff until a bit of vapor comes off.
“Sort of like how ‘inflammable’ means the same as ‘flammable’? Boy, I learned that one the hard way.”
–Woody from Cheers
Did he say “prevent it from fart circuiting” at 3:00 ?
Also wondering how long it will take him to figure out why it stops pumping when it’s pulled too much vacuum for the pump to overcome. Always vent your reservoir!
I carry a small squeeze bottle in my pocket. No arduino needed.
…and it’s virtually useless against this virus as long as it’s just the default alcoholic mixture.
Soap or other washing liquids are much more efficient: This specific virus is protected by a lipid shell which is easily destroyed using soap, thus deactivating the virus. Alcohol is efficient against many bacteria; That’s why alcoholic desinfection products should be prioritized to people who actually need them.
Please, don’t just use alcohol and think the others are protected from your virus!
When I read “no arduino” I expected a footpump. A simple footpump most people use to pressurize their air matras or boat on the beach. So using this you can that with one gentle push, pressurize the jar enough to push out some of the liquid.
Just one jar with fluid and a footpump with an air hose is all you need. No fiddling with electrics or electronics, no pump required and the possible failure(s) are directly coupled by the way you step on the footpump.
Using an electric pump (which hopefully doesn’t degrade by the fluid) is fun too… but in a different way.
I actually went from this style of pump to a siphon + a tap (controlled by a servo). My pump was rusting after a year or so.
https://hw-by-design.blogspot.com/2020/03/stm8-timer-servo-controlled-water-valve.html
Why would you need your sanitizer to be hands free? This is literally where you could sanitize your hands.
Secondly, instead of a pump, a siphon would allow you to dispense without the electronics coming into contact with the alcohol. Simply set the spout below the jar and use a value to control flow. You can use the alcohol’s vapor pressure to prime the siphon.
Same thoughts on a proximity-sensor soap dispenser ad that run on tv a few years back. They tried to instill the fear of the oh-so-dirty pump handle with it’s many pathogens that you were just about to wash off if you used the soap properly
I did not get what “dirty digits” mean, even after googling it (it show some DJ or whatever). Can someone explait it to me?
digit[ dij-it ] noun: a finger or toe.
When doing a battery-powered project, I’ve found the Arduino (or an ATtiny, at any rate) is worth its cost. An IR sensor running continuously takes a surprising amount of power. With a microcontroller, you can turn the IR sensor on and off intermittently and extend the battery life quite a bit. The microcontroller itself takes only a trickle of current, so it’s well worth it.
“a container which used to contain coffee” ….. Maybe I was watching a different video. all I saw was an empty jar of “powered sadness”. :D
How about a system that uses zero electronics? What can be re purposed to make a foot powered bellows and some simple flap valves. I am thinking you step on the bellows, send a blast of compressed air through a flapper valve into something like a soda bottle with two holes in the top. The air goes to the top and a tube comes up from the bottom and out through the top and dispenses your hand goo. When you let off the bellows a spring returns them to their open position and another flapper valve lets the next blast of air to be used into them. Simple, and zero electronics. I can see laser cutting the valve flappers and perhaps 3D printing the return springs. It could be an interesting marriage of recycled kitchen junk and high tech, with some aquarium tubing, and gorilla tape thrown in…