What I mentioned above was just use a store bought bottle of sanitizer and do exactly what this guy did to push the button using a little gear motor and a 3d printed cam. FF to 2:32 if it doesn't automatically:

 

Here's one that uses a centrifugal pump driven by a motor. That actually makes good sense if a major design concern is cost. Tough to beat. All you need is an adjustable one-shot circuit to give you a variable soap delivery.

https://www.instructables.com/id/Unclogging-a-SimpleHuman-Soap-Dispenser/

 

That's not a centrifugal pump. Not sure what it's called but it is a positive displacement pump. As the teeth at the top separate during rotation they pull fluid in at the top gap and the gears pull the fluid around the outside then squeeze it out to the delivery tube.


This is a centrifugal pump:

 

That's not a centrifugal pump. Not sure what it's called but it is a positive displacement pump. As the teeth at the top separate during rotation they pull fluid in at the top gap and the gears pull the fluid around the outside then squeeze it out to the delivery tube.
View attachment 204896

Oops, you're right, it's a PD pump as I speculated earlier, just not a piston.
Is a modern windshield washer pump this type? Probably overkill for this project but easy to find.

Might work:
https://www.sinoning.com/product/sm...r-water-pump-mini-oil-pumping-self-absorption

https://www.ebay.com/itm/Small-Gear...Absorption-0-4L-min-High-quality/192718853546

 

That's not a centrifugal pump. Not sure what it's called but it is a positive displacement pump. As the teeth at the top separate during rotation they pull fluid in at the top gap and the gears pull the fluid around the outside then squeeze it out to the delivery tube.
View attachment 204896

This is a centrifugal pump:

The device with the gear teeth is amazingly enough called a gear pump.
And the easy option to pump a standard dispenser pump would be a cam that lifts against a spring, and then at the end of the rotation releases the spring to press the plunger on the pump. The advantage being that the effort to rotate can be constant for the whole move, avoiding any load peaks that will tend to stall the motor as the batteries age. This should allow the maximum possible battery life.

 

You can just build this circuit

 

The setup in the video seems a bit complex. A motor driving a cam for one revolution is a fairly simple mechanical arrangement and offers completely repeatable amounts every time, even as the battery ages. And since it uses only one revolution it can get away with a very simple magnet and reed switch, or microswitch driven from the same cam, to stop in the right place every time. If the mechanical part is done right there would not even be any electronics needed, just a start button and the cam operated switch to complete the revolution. About as simple as it can get.

 

I'm late to the party and probably missing something here, but if the purpose of automating the sanitizer pump is to avoid contamination, then won't any solution involving a push button defeat that purpose? Foot-pedal operation or triggering would arguably give less risk of contamination.

 

I'm late to the party and probably missing something here, but if the purpose of automating the sanitizer pump is to avoid contamination, then won't any solution involving a push button defeat that purpose? Foot-pedal operation or triggering would arguably give less risk of contamination.

Either a motion sensor or a photo-electric "beam break" sensor will be a no-touch type of control that is simpler to operate. and probably a lot simpler to implement. There is also another scheme using the variation in ambient light, quite similar to the motion sensor systems, that just needs a move over the sensor instead of needing a light beam to break. (I just thought of that one.)

 

That's not a centrifugal pump. Not sure what it's called but it is a positive displacement pump. As the teeth at the top separate during rotation they pull fluid in at the top gap and the gears pull the fluid around the outside then squeeze it out to the delivery tube.
View attachment 204896

Similar to the peristaltic pump, but where the fluid does not come in contact with the pump mechanism, per-se.
Max.

 

Similar to the peristaltic pump, but where the fluid does not come in contact with the pump mechanism, per-se.
Max.

The correct name for a pump that has gear teeth in contact with the working fluid is given in post #25. You can verify that in wickipedia.

 

The correct name for a pump that has gear teeth in contact with the working fluid is given in post #25. You can verify that in wickipedia.

I was not attempting to dispute that, but to show a parallel or comparison to the peristaltic pump in appearance !!
I have worked with enough pumps to know the difference.
Max.