Mechanical design question (vertical lift with servo) & stepper question

Projects General Guidance
1

I know this is bordering on not really being an Arduino based questions..

but I will be controlling the servo? for this task..... and who better to ask than the collective brain trust of the members here? :slight_smile:

So I have some liquor optic measures (devices that secure to your liquor bottle and dispenses measure amounts of said liquid)

I have these: (which I prefer to use)
http://www.beaumonttm.co.uk/bar-products-and-accessories/spirit-measures-accessories/spirit-measures/metrix-sl/

and this style: (which Id rather save for another project..but if happens to make things MUCH easier, I may switch)
http://www.beaumonttm.co.uk/bar-products-and-accessories/spirit-measures-accessories/spirit-measures/solo-classical/

I am looking for a nice and easy (preferably somewhat cheap/affordable) way with a somewhat small as possible footprint to be able to dispense this liquid.

I will have a 'tray' that is being moved left/right and stopping under each 'bottle'.... at this point I need to trigger a servo/linear servo to vertically lift up and dispense the liquid.

I saw this video:

But I cant clearly see how/what they are using as the mechanical parts? I see the hobby servo? but what is making contact with the 'shaft' that comes out of the optic/dispenser?

The 'shaft' can only go up... its not a 'pull/trigger' type... but a vertical movement.

The travel is pretty small as well.. I havent measured... but roughly 1-2inches tops.. (probably more towards the 1 inch side of things)

I tried to for some linear servos... but they were either tiny/hobby look devices (that didnt seem to fit the build).. or the one that seems to fit was like $70 or so!!

PQ12-R

https://www.actuonix.com/Actuonix-PQ12-R-micro-linear-servos-for-RC-p/pq12-r.htm

The fastest one is the only one that I think may work.. but the price is kinda high.
Bonus is seems run on 6v

I didnt think a hobby servo would have enough torque.. but the video seems to show otherwise?

I just cant wrap my brain around HOW its working.. since the hobby servo 'arm' will move in a circular motion.. where it needs to be vertical? So some sort of attachment that keeps contact with the 'stem/arm' of the dispenser.. and lifts it up even though the arms is going in a circular pattern?

A door actuator would be fast enough... but the ones I see for car doors..etc seem a bit to big!

Last question (to qualify this post to be on the Arduino forums!) LOL

I have my stepper motor working as I expect (as far as speed and movement)

Nema17
1/16 micro stepping
DRV8825 driver board

Currently.. I have things mocked up in a breadboard (which may be part of the problem here)..

with my driver, Arduino...etc..etc all on the breadboard.

I am powering the Arduino via USB ... and the stepper motor being powered by a benchtop PSU...

GND's connected on the breadboard.

I notice that my stepper motor make noise/whines (not sure how best to describe it)... as soon as its powered on.

Not even moving.... just sitting still awaiting a new 'command'...

I send serial data to the Arduino.. it gets parsed.. and I navigate the stepper to where it needs to be.

What can be done to eliminate this noise/whine coming from the stepper motor?

Thanks..

2

xl97:
I just cant wrap my brain around HOW its working.. since the hobby servo 'arm' will move in a circular motion.. where it needs to be vertical?

A small segment of a circle can approximate a vertical line. The larger the radius, the less the curvature. So if you have an arm attached to the servo that is not rigidly attached to the optic, then it can be made to slide back and forth enough to accommodate that curvature.

If you're really hung up about truly linear motion then you could use a stepper and leadscrew like the Z axis of a 3D printer:

3

Might be able to just find a suitable selenoid to push up the dispenser plunger.
One selenoid per bottle would be way easier to control and then you just need to get the glass roughly centered under it.

4

Have you measured the force necessary to push up the dispenser to make it work?

I have always been on the other side of the bar but it seems to me a fair amount of force is required. Easy for a person, but maybe it would need a powerful servo. Also 25mm is a quite long distance for a servo. If you put a longer arm on a servo the available torque reduces.

Whatever device you use make sure it can provide at least 50% more force than is actually required.

...R

5

Take a look at this: https://www.theinebriator.com/techie-stuff/. They're apparently using a DC motor to push a plate against the optic. It sounds like less hassle than trying to macguyver a servo linkage.

6

Hi,
This may give you some inspiration, I think there are 2 more parts after this.

Tom... :slight_smile:

7

Thanks for the reply guys! (been a busy day at work..... just getting around to respond now!)

  • I have watched many videos of people who have done similar projects to what I am doing....
  • I am trying to stay away from a 'lead screw' type of approach. I dont have A LOT of room in my current placement of things...which is why an alternate linear servo (cheaper) then the one I linked to would work.. or some sort of 'servo linkage' :slight_smile:
  • most of the videos I have watched use a lead screw type of approach... but they are (most) are using the second style of optic measures.. which has an 'odd' shaped bottom to make contact with.... have a 'tri-star' type of lever,.. and the liquid dispenses from the center/middle (so usually you will see 'circle' type platform/3D printer part making the contact.

** One of the reasons I prefer the first style of optic measures. :slight_smile:

@Robin2 I have -not- measure the force. I'm not exactly sure HOW to go about doing so?

Unless I can source/find a cheaper linear servo like the one linked to.. I guess I'm going to try and follow up on the 'lever' style approach.

In that video.. the more I watch,.. I can sorta see the lever on the left side... hanging/extruding off of the 'arm' connected to the servo. I'm not clear how that would work in my set-up.

It looks as if the 'lever'.. is already connected to the optic dispenser? Which works for STATIC dispensing (ie: a dedicated servo for each bottle)

Are there any knock-offs/clones of that PQ12-R linear servo perhaps out there? (although 20mm might not be enough.. I really need to get a precise measurement of that)

Perhaps there is a small/tiny car actuator out there?

  • should run on 12v (I'll have 5v & 12v lines in this project from a PC PSU)
  • should MORE than fast enough
  • should have enough torque/power

*** can one be found that is small enough though?

8

xl97:
@Robin2 I have -not- measure the force. I'm not exactly sure HOW to go about doing so?

Could you push it up with a kitchen scales?

...R

9

xl97:
a dedicated servo for each bottle

That's what it looks like to me.

10

bummer...

it looks (looked) like a nice approach (at first)

11

I doesn't mean you're forced to do the same if you prefer a single servo mounted on the X axis.

12

hmm... looks like this guy is just using a hi-torque servo... and an extension of the arm piece?

*(same optic dispensers too)

edit:

holy crap!.. that servo is like $90.00 lol

Hitec HS-7955TG servo motor

better off getting that linear servo above.

13

pert:
I doesn't mean you're forced to do the same if you prefer a single servo mounted on the X axis.

Correct!

But I'm not clear on HOW I am going to go about doing that.

I believe (if going the regular hobby servo route).. I can use 1 or even 2 servos..

The servos will be mounted on either side of the 'dispenser lever'..

I'm hoping that makes it easier to 'lift/push'... being there are two.

I'm still not clear on the mechanics.. or the custom 'arms' I need. As you pointed out above.. a small segment of the 'circle' can be a straight line..

I have an idea I'll post a quick drawing of when I get to work.

Still lkooking for a cheap/clone of they linear actuator/servo above..

Still thinking perhaps a scissors lift and servo might work too.. (havent found any scissor lift products however)

14

xl97:
I'm still not clear on the mechanics.. or the custom 'arms' I need. As you pointed out above.. a small segment of the 'circle' can be a straight line..

The custom arm can be made out of a piece of wood or metal or plastic. Servos usually come with a variety of "horns" that provide convenient mounting holes. Other people seem to be having good luck with one servo so I'd try for that to start because two servos increase the complexity. The question is how much torque will you need to reliably operate the optic? I have noticed that the price of servos goes way up as you start getting to the higher torque models so it might end up being cheaper to use two lower torque servos, but at the cost of increased complexity. I don't think it will take a tremendous amount of force to operate the optic but I've never used one.

My advice is to ge "hands-on" with this problem. Hold a pen in one hand. Hold an optic in the other. Rotate the pen as it would do when mounted to a servo. Now you can start experimenting with different lever lengths to see how that effects the pseudo-linear motion. Sometimes a simple exercise like this can make things clear in a way that endless though experiments and Internet research can not.

xl97:
Still thinking perhaps a scissors lift and servo might work too.. (havent found any scissor lift products however)

My experience is once you start getting into any specialty product without a large customer base the price goes way up. I suspect your scissors lift would fall into that category unless you can repurpose some commodity product. The great thing about the recent popularity of 3D printers and other CNC products is it has brought the price of linear motion solutions WAY down, even for people who need it for another purpose. You even have multiple solutions: leadscrew and timing belt to drive the linear motion, round linear rails and 2020 aluminum extrusion for linear guides. All ridiculously cheap if you don't mind waiting for shipping from China. I don't think any of that will be needed to actuate your optic but if you're going to search all over for a scissors lift you should definitely consider that instead.

15

@pert

thanks for the replies.

All valid points. I am currently using a linear v-rail/slot and a stepper motor to move the main 'x' axis around... (close to 2020/makerslide..etc..etc.

this 'x-axis' main purpose will be to move the cup/holder around... and position it under the optic/bottle opening.

I was hoping to hitch a ride on that tray (so to speak) and somehow mount this servo close to the optic/lever..

another stepper would do the same I suppose? (this was my first stepper motor project)

Although I still would need to figure out the mechanics portion of that as well (mini belt? leadscrew? <- would it be fast er enough?)

I guess its early enough to still be open to something that 'fits'.. and works visually as well..

I have a laser cutter.. perhaps I'll try cutting out some 'horns'.. and gets hands-on as you say. :slight_smile:

thanks.