Mini Elevator - What motor should i use?

Hello, I'm thinking of making an elevator model and I was thinking of using a stepper motor? I want a motor where I know it's position. Like a servo for example when you set its value at 800 it goes to a certain position. Is the stepper motor the best choice?

The reason I need to know its position is because I need to tell it at what exact position to go for a specific floor. and also I need to be able to adjust the position after i program the arduino. So i will have an lcd display and buttons to adjust the position of the motor depending of the position of the elevator and the floor it is at.

Thank you. Appreciated.

A stepper would allow you to very accurately control the position at which the elevator stops, without the restriction imposed by the ~180° movement of a servo. However, real elevators don't use steppers since they are loud, relatively low power and inefficient. If you want to approximate a real elevator, a simple DC motor would be a better choice. You can still control the position of the elevator by using limit switches, and/or hall sensors or optical encoders to count the revolutions of the motor.

Stepper motors can "slip" or miss steps which would throw out your destination point.

A better approach would be to use for example an optical vane switch set at each level.

A small dc motor could drive your lift via speed reduction e.g. belts and pulleys or gearbox.

Care would have to be taken to allow for the motor to stop after the lift encounters the switch.

If you use a stepper motor you will need at least one limit switch so the Arduino can (for example) make the elevator go all the way down until the switch is triggered. That way the Arduino will know the elevator is at the zero position and it can count steps from that point onwards. Without the limit switch the Arduino will have no means of knowing where the motor is - quite unlike a servo.

Have you considered a sail-winch servo which gives position control over about 3 full revolutions.

As others have said a geared DC motor and detectors at each level would probably be the most prototypical solution.

…R

Dependent on how small it is, you could possibly just use a cord going to a linear potentiometer to act as feedback for posistion. With a few pulleys you could easily gear down the movement to keep it within the potentiometers full range.

Dependent on how small it is, you could possibly just use a cord going to a linear potentiometer to act as feedback for posistion. With a few pulleys you could easily gear down the movement to keep it within the potentiometers full range.

I had a very bad experience positioning a thing by means of linear potentiometers: they have mechanical gaps that made them unappropiated.

I think that limit switches (optical, hall, whatever) and a DC motor (properly geared) is a good approach

Regards

vffgaston: I had a very bad experience positioning a thing by means of linear potentiometers: they have mechanical gaps that made them unappropiated.

They shouldn't "have gaps" but nonetheless, It's not the method I'd choose. I merely mentioned it as an alternative solution.

Personally I'd probably go for strategically placed reed switches and a magnet on the lift.

They shouldn't "have gaps" but nonetheless, It's not the method I'd choose.

You are completely rigth: the system had mechanical uncertainties (I don't know how to translate "holgura": it refers to the different readings-for the same position- due to small mechanical "tolerances"?)

Thanks for your patience. Regards

vffgaston: You are completely rigth: the system had mechanical uncertainties (I don't know how to translate "holgura": it refers to the different readings-for the same position- due to small mechanical "tolerances"?)

I think we'd normally call it latitude.

the correct way is to use a sensor and a home button. one on each floor. any mechanical device that runs the length will have changes in temperature. using a stepper is fine, if you like steppers and you also use a home sensor.

one way is to use a black/white section near the floor, then once in that section, start to slow the motor. then at the final sensor, stop.

the more accurate you want to be, the better the sensing.

if you look at a incremental encoder, you can use 2,3 or 4 reflective sensors and position exactly. http://www.electronics-tutorials.ws/io/io_2.html

or for an absolute encoder http://mechatronics.mech.northwestern.edu/design_ref/sensors/encoders.html

each floor would have one. you just need to approximate getting to the right floor, the final destination would be by your encoder.

laser print, use reflective sensors, all very easy and can be very precise.

latitude

latitude?

vffgaston: latitude?

A measurement is said to have some "latitude" if it may return some figure within some range rather than a specific figure. It seems a strange use of the word, but that's what it means.

Hi, For what it's worth I'd go for a stepper motor with a micro switch at the top and bottom, so you can always check if the lift is there or not. With evenly spaced floors, it will be so many steps to the next/last floor, Keepping a running count will tell you what flloor you are at.

There are many stepper driver modules, that only require a signal to step (LOW to HIGH) and a signal for DIRection (LOW/HIGH), leaving lots of pins for other things.

See: http://www.ebay.co.uk/itm/371203923761?_trksid=p2060778.m2749.l2648&ssPageName=STRK%3AMEBIDX%3AIT http://www.ebay.co.uk/itm/361107960371?_trksid=p2060778.m2749.l2648&ssPageName=STRK%3AMEBIDX%3AIT

Hope it helps. Regards

Mel.

A measurement is said to have some “latitude” if it may return some figure within some range rather than a specific figure. It seems a strange use of the word, but that’s what it means.

The forum is a good oportunity to improve english.

Latitude seems to translate to spanish as “tolerancia” (what, by it’s side, seems to have a literal translation on “tolerance”; I have been consulting google translator and looks that tolerance has, in english,one of the meanings that tolerancia has in spanish -the one concerning, for instance, social tolerance about religion, habitudes and so on).

I have asked my daugthers and son in law, that are engineers and work in England, for the translation of holgura: My son has answered by writing: "Slack or play or looseness "

In fact an holgura is caused by mechanical wearing while the tolerancia is what you explain: “A measurement is said to have some “latitude” if it may return some figure within some range rather than a specific figure”; in drawings and blueprints it appears as a “main figure” plus (minus) one (or two) much smaller fugure(s).

Conclusion: you are rigth, the allowed latitude in a mechanism (linear pot) causes uncertainty in the position of the cursor (fortunately, cursor is the same in spanish). The holgura (slack) will cause a bigger one.

(I had this problem while working -I’m engineer too-; the case was of a machine that had to position a pivot within a ± 1 mm latitude in an span of up to 2.000 mm. The supplier sent initally the machine with linear pots installed; they had to change them by encoders).

Best regards

Interesting. I don't think I have ever come across lattitude in an engineering context (apart from with longitude). I have come across it in the context, say, of whether to punish someone for a minor offence or to allow him/her some lattitude. I guess that is the same idea.

Tolerance, variability, slack, slop and play are words I would associate with uncertainty.

...R

Robin2: Interesting. I don't think I have ever come across lattitude in an engineering context (apart from with longitude). I have come across it in the context, say, of whether to punish someone for a minor offence or to allow him/her some lattitude. I guess that is the same idea.

Tolerance, variability, slack, slop and play are words I would associate with uncertainty.

...R

Pretty much the same here. I would also include repeatability and precision.

Robin2: Interesting. I don't think I have ever come across lattitude in an engineering context

Funny enough, now I come to think of it, I don't think I've heard it used this way for quite some time. My understanding of it is the deviation of expected results due to wear or other imperfection in the system. Yet I can find no reference to it used like this on google. Perhaps I just dreamed it :)

Robin2: Interesting. I don't think I have ever come across lattitude in an engineering context (apart from with longitude). I have come across it in the context, say, of whether to punish someone for a minor offence or to allow him/her some lattitude. I guess that is the same idea.

Tolerance, variability, slack, slop and play are words I would associate with uncertainty.

...R

I would say that variability, tolerance and latitude are synonyms.

I'm afraid the issue about tolerance, latitude, etcetera has become an emerging star; I beg for OP perdon.

Two issues:

1) In mechanics you always have an uncertainty: it is according to the project itself (two pieces of wood that have to assemble; a shaped glass that has to fit on a frame; a piece that belongs itself to a precission machine; an aerospatial component, etcetera) and it forms part of the basic design data. For instance, in the case of the mini-lift (sorry; elevator :cold_sweat: ) possibly +-1 mm would be acceptable.

2) Coming back to lexicology: it has happened to me many times that I use a word in english say "without thinking" (I mean, most of the words I use in english I do not think on them before in spanish; when I am writing or speaking in english I do think directly in english). Then I start thinking on the word (if it is correct); it happened to me this time with tolerance (as a technical sinonymous of latitude -that, on the other hand, i'm pretty sure i've never used in mechanics). Do some of you think it can be used with this meaning (a plus minus acceptable measure . . . .)?.

Best regards

I would think so....given the following...

synonyms: freedom, scope, leeway, elbow room, breathing space, space, room, flexibility, liberty, independence, play, slack, free rein, free play, licence, self-determination, room to manoeuvre, scope for initiative, freedom of action, freedom from restriction, a free hand, margin, leisure, unrestrictedness, indulgence, laxity;