Hi guys,
So I was thinking about how if everyone touches the top of a soap bottle like this, it can possibly spread through there.
In public places there are automated soap dispensers. However, to get one at home, they appear to be $30-50 on Amazon.

So I was thinking if I got a solenoid a couple ICs and a distance sensor of some sort, I could automate it fairly easily. However, I am not sure what specifications I would want for the solenoid, and if I should use an ultrasonic or a light based distance sensor.

Also, I would need help with the circuit if it is many comparators and logic. It seems like a microcontroller is added cost.

The end goal is to automate a normal soap dispenser for $5 or less (excluding shipping). This is more of a proof of concept type thing to show that DIY can help keep things sanitary for less.

 

One problem is the viscosity of liquid soap making simple gravity feed about impossible. Liquid soap also does not come in a pressurized container like for example shaving cream so use of a simple cheap solenoid valve isn't likely to work.

Triggering could be done using a simple and cheap PIR sensor module. A Google of PIR Sensor Module will bring up a wide range of them. That takes care of the sensor. Next we need a timer scheme and a simple 555 timer one shot design could take care of thet or just Google One Shot Timer and buy a ready to go module. The trick is then how to dispense the soap or hand sanitize solution?

Ron

 

The one shot/monostable thing makes sense, but I would have to learn a bit more how to set up the 555 timer. I also will need to find the best deal on the PIR sensor but that definitely should work.

I'm thinking that a solenoid just presses down on the top with enough force that it is like a hand pressing it down. Then I somehow attach it. Not a valve or anything like that. However, where could I get a reasonably powerful solenoid for a couple of bucks? What specifications should I look for?

 

What needs figured out is how to get the liquid from bottle to hand. It's actually hard to duplicate those little hand pumps electrically. Hand soap is too thick ruling out gravity feed.

A Google of 555 One Shot timer (non retriggerable) will bring up circuits, the out pulse duration needs figured into this. Also the 555 timer chip uses a negative going trigger to start things so if possible you want a PIR sensor which is Active Low out.

Ron

 

In public places there are automated soap dispensers. However, to get one at home, they appear to be $30-50 on Amazon.

That's a bargain for an engineered solution. How much do you value your time? By the time you MacGyver something, you'll be in way more than $50 in time and materials.

 

I would be thinking more of a linear motor or a servo/gear motor than a solenoid.

 

... As far as an efficient actuator, there is a type of threaded rod called ACME thread that is used for motion type applications, rather than fastening. A small diameter ACME threaded rod, maybe 1/4" or so, could be energized in a fixture by a stepper motor to provide sufficient force to compress the push button on a hand soap bottle. An arduino would control the forward and reverse movement of the plunger. Some type of motion sensor could initiate the sequence.
.. It looks to be feasible, as far as the construction goes.
ACME threaded rod
... It may be that it would be necessary to somehow allow the ACME Nut component to compress the push button, rather than the rod, for positioning convenience. That is, the modified nut would be the verticle moving plunger part, rather than the rotating rod.

 

... As far as an efficient actuator, there is a type of threaded rod called ACME thread that is used for 'motion' type applications, rather than fastening. A small diameter ACME threaded rod, maybe 1/4" or so could be energized in a fixture by a stepper motor to provide sufficient force to compress the push button on a hand soap bottle. An arduino would control the forward and reverse movement of the plunger. Some type of motion sensor could be the initializing trigger.
. .. It looks to be feasible, as far as 'execution' goes.
ACME threaded rod

I actually gave that some thought but discounted it. A linear actuator could be used but often we need to pump the hand dispensers like the one pictured a few times.

That's a bargain for an engineered solution. How much do you value your time? By the time you MacGyver something, you'll be in way more than $50 in time and materials.

This I agree with strongly. I mean as a college or school project it could be interesting and get students thinking but as to making a home brew solution even at $30 ~ $50 it's a good deal. When I suggest things I normally try to implement turn key or modular solutions. Sort of a connect the dots.

Ron

 

That's a bargain for an engineered solution. How much do you value your time? By the time you MacGyver something, you'll be in way more than $50 in time and materials.

It's more of a proof of concept thing that if you can solder some things together it can be much cheaper, plus with isolation, there is less to do anyways.

I would be thinking more of a linear motor or a servo/gear motor than a solenoid.

Okay, maybe. But would I be able to get a motor like that which is powerful enough and cheap enough?

... As far as an efficient actuator, there is a type of threaded rod called ACME thread that is used for 'motion' type applications, rather than fastening. A small diameter ACME threaded rod, maybe 1/4" or so could be energized in a fixture by a stepper motor to provide sufficient force to compress the push button on a hand soap bottle. An arduino would control the forward and reverse movement of the plunger. Some type of motion sensor could be the initializing trigger.
. .. It looks to be feasible, as far as 'execution' goes.
ACME threaded rod
... It may be that it would be necessary to somehow allow the ACME 'Nut' component to compress the push button, rather than the rod, for positioning reasons.

Sound slow and difficult to implement or not powerful enough.

 

Perhaps some sort of peristaltic pump would be better.

I’d design a bag with an extended neck. The bag would be mounted with the neck facing down. A cam mounted on a stepper motor would squeeze the soap out with peristalsis. The rest of the bag would rest in a chamber, where a weight would assist gravity in pushing out the soap.

You wouldn’t need an Arduino (nor PIC, etc...). A simply ATTiny would serve as a driver.

 

A solenoid that is AC powered, 120V and had sufficient force was used several years ago to construct an animal feeder. It worked as planned. When power was applied, a feeder cup moved causing its lid to drop out of the way. The motion of the solenoid core slug, when activated, was a retraction of maybe 1/4". Consequently, it would be necessary, in your application, to fabricate an arrangement that pulled the dispenser button down when power is applied, maybe with the solenoid body situated underneath the dispenser bottle. A metal harness to capture the dispenser button could be attached to the solenoid core in some manner.
A search of the original solenoid supplier, an industrial supply house, did not yie!d any stock of the previously used solenoid. It would be necessary to locate an acceptable part, with sufficient force and core displacement specifications.

 

Is there a problem at all here, or are there some habits that need to be changed?

Before the disinfection, you have potentially some virus on the hands and top of the pump bottle.

After pressing the pump, you do not need to touch the bottle again, but can just distribute the disinfectant over your hands.

 

Had I to attempt this myself, I would focus on imitating the finger/hand exerting pressure on the existing dispenser.

Doing otherwise means reengineering the whole thing, making that mythical 5 USD cost possible if you build 6 million units minimum.

EDIT/
In line with post #3
/EDIT

 

For an actuator I would use a geared motor with a cam or crank to to press the button on the dispenser. There would also be disk with a notch in it which operated a micro switch. Use the contact on the micro switch that was open at the notch position and closed when not at the notch position between the power supply and the motor. This would cause the motor to rotate until it reached the notch and then stop. A pulse from the PIR when it first sensed the presence of a hand would trigger the motor on for long enough for the motor to move away from the notch. It would then complete a revolution. I agree with the other comments that it would be cheaper to buy one than make it. I think I have seen them on offer from aldi and lidl for less than £10.00

Les.

 

What I once saw in a medical installation for surgeons to was up with was a sink with foot pedals to operate the water valves mechanically, and a separate pedal that worked a mechanical flex-cable to drive the soap pump. No electrical stuff at all. No batteries or external electric power. That was in another part of the world but certainly such could be created to operate a standard pump type of soap dispenser today. Fairly cheap and quite reliable and it would offer a level of control quite challenging to have with an electrical powered dispenser. Of course, the down side is it would not be "stupid-proof", and so it could not be used in public areas.

 

I agree with Kjeldgaard (post #12) re the dispenser, but there is still a problem; how to turn off the water tap without re-infecting your hands after washing them. This does require a change of habits since both hands and tap would have to be washed.

 

https://www.banggood.com/Intelligen...Xiaomi-Youpin-p-1481537.html?cur_warehouse=CZ
by
https://www.google.com/search?q=liquid+hand+cleaner+servo+dispencer

 

I agree with Kjeldgaard (post #12) re the dispenser, but there is still a problem; how to turn off the water tap without re-infecting your hands after washing them. This does require a change of habits since both hands and tap would have to be washed.

In many airports flushing toiletts and opening the faucet is started approaching a hand to acertain point.

 

In many airports flushing toiletts and opening the faucet is started approaching a hand to acertain point.

We had a "hands free" restroom where I worked. Automatic door(s), automatic toilets, automatic had soap dispensers and automatic water in the sinks. During the winters if I came in from the back loading docks when it was freezing and snowing the automatic urinals wouldn't work. The PIR sensors were looking for IR (heat) and until you warmed up they had no idea you were there, so manual flush backup. Never looked at a soap dispenser up close to see how they worked.

Ron

 

For faucets, there are already available alternate handles designed to be used to shut off the valves by means of pressure from the back of the upper wrist. Those handles are available from Home Depot and many plumbing supply stores. The advantage is that no plumbing changes are required, and so no expensive plumber need be called. In addition, no electrical supply or batteries. Plus, a pair of the handles costs a lot less than one solenoid valve.
It seems that all of the "low tech" answers are ignored here.