Where could I find DC very low RPM very high torque motor ?

Using Arduino Motors, Mechanics, Power and CNC
1

Hi,

I would like to replace my hand turning this :

With a motor controlled by android and a battery. Do low RPM (20 to 60 RPM) high torque motor exist at low cost ?

I don't want to use a AC motor with electric wires...

Thank you very much.

2

kaescrat:
Hi,

I would like to replace my hand turning this :
http://www.cyberfanny.com/decoration/local/cache-vignettes/L460xH307/04-90c7b.jpg

With a motor controlled by android and a battery. Do low RPM (20 to 60 RPM) high torque motor exist at low cost ?

I don't want to use a AC motor with electric wires...

Thank you very much.

Stepper motor - there was also another post recently - someone asking about an auto door opener and someone else posted in there about a small DC motor he was using to open and close his blinds.

Let me see if i can dig it up in a little while

Craig

3

are gears an answer ?

4

craigcurtin:

kaescrat:
Hi,

I would like to replace my hand turning this :
http://www.cyberfanny.com/decoration/local/cache-vignettes/L460xH307/04-90c7b.jpg

With a motor controlled by android and a battery. Do low RPM (20 to 60 RPM) high torque motor exist at low cost ?

I don't want to use a AC motor with electric wires...

Thank you very much.

Stepper motor - there was also another post recently - someone asking about an auto door opener and someone else posted in there about a small DC motor he was using to open and close his blinds.

Let me see if i can dig it up in a little while

Craig

Here you go - these are the motors he linked to

http://www.maplin.co.uk/miniature-epicyclic-motorgearboxes-43376

Here is the actual post

http://forum.arduino.cc/index.php?topic=183051.0

I personally think a stepper motor is a better idea but both will work

Sparkfun have the easydriver and a bipolar stepper that works well together

Craig

5

Thank you very much for your answers. I though

  1. sparkfun motor would not be powerful enough.
  2. stepper motors would be blocked after 360° like servos I already worked with
6

kaescrat:
Thank you very much for your answers. I though

  1. sparkfun motor would not be powerful enough.
  2. stepper motors would be blocked after 360° like servos I already worked with

The stepper motors are plenty powerful enough and they have unlimited turning.

If you look up NEMA 17 motor on EBAY there is a good selection for less than $25 - then the easydriver from either ebay or sparkfun for around $15 and you are good to go - you will need to work out a coupling mechanism to attach it to the rod that turns the winder

Craig

7

But first you need to put a figure to that "high torque" requirement - some sort of measurement or
calculation and then add a healthy margin for error. You might want to consider limit switches - too
high a torque might damage the mechanism if it tries to force past the end-of-travel.

8

Some similar post.

https://www.google.com/search?as_q=blinds&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=http%3A%2F%2Fforum.arduino.cc%2Findex&as_occt=any&safe=images&tbs=&as_filetype=&as_rights=

9

How slow do you need it to turn?

Probably a 60-120 RPM DC gear motor would work fine - perhaps something like:

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=HAR&Product_Code=TM02MTR4597&Category_Code=DCGEARHEAD

or

http://www.mpja.com/12VDC-140-RPM-Gearhead-Motor/productinfo/18746%20MD/

???

There are tons more out there where those came from; they would likely have all the torque you would need for your application and then some (let that be a warning to make sure you set up some kind of limit-switch mechanism).

10

Nice answers, thank you.

Why should I choose a stepper motor over a gear motor. Or the opposite ?

How could I calculate the torque needed ?

11

torque needed,
you make a good guess,
based upon any measurements you can get,
if you have a set up, torque is force times distance,
so ruler and scales or weight, then add significant safety margin, ( 4 to 10 times )

dc v stepper.

dc ( on / off ) , simple low cost, easy to control ,

stepper , can be very accurate , have fine control over acceleration, speed , and breaking.

12

kaescrat:
Nice answers, thank you.

Why should I choose a stepper motor over a gear motor. Or the opposite ?

How could I calculate the torque needed ?

For what you want to do a stepper will i believe be easier - you have a set number of turns of the winding rod (i assume you intend to leave the rod connected for manual control)

With a stepper motor you can tell it to do an exact number of turn (in fact depending on the stepper you can break an individual turn into many many many steps.) This gives you much more control and enables you to deliver a lot of torque also.

I personally would go for this combination

I have used this combination for many things in the past - currently i have an automated chook door that has been running for 3 years without a problem.

Craig

13

What about these Pololu - Motors and Gearboxes

...R

14

I tried to rotate the crank by hands directly with the bar (not using this part : http://www.sainthimat.com/images/11E79696-845B-D184-CBE0-708249E03F2D/46881.jpg ) and it's impossible. So torque may be really challenging for a little motor...

15

"given enough leverage , and a strong enough fulcrum, I could move the world,"

gears trade off speed for torque.

stick handle in, so its horizontal. measure how long handle is,
measure weight needed on end to move handle.

weight times distance is torque.
( use Kg and meters , or Lb and feet )

16

kaescrat:
I tried to rotate the crank by hands directly with the bar (not using this part : http://www.sainthimat.com/images/11E79696-845B-D184-CBE0-708249E03F2D/46881.jpg ) and it's impossible. So torque may be really challenging for a little motor...

Are these security screens ? I assumed they were blinds the first time around from the picture ?

Well you can invest $30 in the solution i proposed and see how it goes - if no good then you will need to step it up to the next level - before you go much further i am wondering if you have thought about how you are going to mount all of this so it looks OK ? Obviously adding additional gearing steps will let you get as much leverage/torque as you need -- but things will become less and less sightly as you go

Craig