PDA

View Full Version : High Torque Stepper Motors For Micromouse



ankitmutha
10-23-2008, 07:35 PM
hi all,

I jus bought a pair of stepper motors for my micromouse from Robokits
(http://robokits.co.in/shop/index.php?main_page=product_info&cPath=2_4&products_id=169) for Rs.600 each!!!!!!!

They say the motors have a high torque ( 5Kgcm ).
But i doubt this.

I asked them for datasheet or catalog of this product from its makers.. anything that could support their claim. but they failed to provide any authentic document regarding this.

The motors have following make:
Minebea Co. Ltd
Type: 16PU-M301-G1

I checked out the web pages of this company minebea but they dont list any motors of theis type(16PU-...)

Anyways i dont care wat make are the motors only thing that matters is that they should provide the amount of torque they claim. 5Kgcm...!!!
But i am unable to get such torque.

I consulted them over this and they suggested me to use L298s to control these.. but even then they dont have that power..

My doubt increases by the fact that other motors available at TRI india costs just 270 bucks but have the same current and voltage specs...
I dont know wat makes more torque but if the volt and current specs are same will they have any difference in the torque??

I would request anyone who has used these motors before to come up and tell me are they worth the price tag and if so what is the best way to get the maximum out of them.

Also others can help out by clearing that doubt about the specs and torque relation..




To mods..
u may feel this post to be irrelevant but i would request u to reconsider as Robokits is a popular brand in india and everyone should know if their motors are worth the money, before investing.

allbits
10-23-2008, 09:39 PM
These motors cannot give 5Kgcm @6V and 500ma.

But i did not see the 5Kg spec at the given link either. Was it advertised, as 5Kgcm at the time of your purchase?

5Kg cm torque is HUGE, by hobby standards. And it draws in equally huge current, at 5Kg.

However, to get maximum torque out of whatever motor you have, check these:

>use bipolar mode.
>Use lithium batteries.
>Use L298, or better ones.
>your speed. at high speeds, the motor tends to slip.

These motors normally have incorrect rating. most of them are designed to work at around 24V.
The motor at TRI , at the time of my writing, costs just 145 rupees, but 12V at 160ma. that has to give very low torque, you may not be able to do much with these unless you tweak a lot.


There was a discussion about steppers some time back, you can do a search at the motors forum.



:arrow: Normally, all these motors were meant for printers, and old generation machines, they are not in production now, and all the surplus are being sold out now. Dont get fooled by claims of high torque for these motors, of THIS size.

ankitmutha
10-23-2008, 11:22 PM
@allbits

yes at the time of sale i asked them via a mail and they told me that they would give 5Kgcm.

i am using following to drive the steppers:
1)12.6v Li-ion batteries
2)bipolar mode
3)L298
4)speed is about 100rpm but the torque doesnot change much even if i reduce the speed.
they claim max speed to be 150rpm.. which i think is correct..

i read that post.

I would like to inform one thing about these motors:
They have very low resistance.. 5ohm per coil...??

i read in that post that if u supply 12-24v directly to common of one phase torque increases...
is it correct??
do i need to overdrive these stepper?? If yes wat voltage would be good..?
Do i need to put two separate 7812 for both the motors to increase torque?? (mentioned in that post.. but seems senseless to me..!!)

allbits
10-24-2008, 12:30 AM
what torque do you want?

ankitmutha
10-24-2008, 12:51 AM
@allbits
my aim is to drive a 700gms micromouse as fast as possible from these motors.
if weight is too much it can be reduced a bit.

wheel dia is 6cm.
that means at 150rpm it would have a lateral speed of 47cm/s!!!
that would be nice if it could carry the weight of the mouse along with it at this speed.

ashish_agarwal123456
10-24-2008, 04:10 PM
for micromouse purpose these motors will be great..... a current of 2A per phase is more than enough to carry upto 1Kg. ( i am comparing with those 75ohm unipolar steppers from floppy drives. even they were able to carry my umouse of 800gms). as far as relation between torque and speed is concerned its fairly constant upto 200steps/sec. so dont worry about that.

and yes... saw you LF video.... it was great!!! good job there.....
what about the second round??

abhijit8
10-27-2008, 03:48 PM
You can get (below 10 ohm) stepper motors at Bombay Electronics in Mumbai (Lamington Road). Go there with your DMM and you will definitely find a good pair of stepper motors.

Use either L297+L298 (http://www.google.co.in/url?sa=t&source=web&ct=res&cd=1&url=http%3A%2F%2Fwww.st.com%2Fstonline%2Fproducts% 2Fliterature%2Fds%2F1334.pdf&ei=h5MFSej1IYvQ6gPxxsXvDQ&usg=AFQjCNFCqnNUp18elUgaNYq9Wfg9epl_nQ&sig2=464gFCOfxfl8Lt5sXdy-SQ) or other stepper motor drivers( e.g A3982 (http://www.allegromicro.com/en/Products/Part_Numbers/3982/3982.pdf)) to overdrive them.

Though its often difficult, you may get free samples of stepper motor drivers from Allegro (http://www.allegromicro.com/).

Also if you are too keen in high torque stepper motors, you can consider buying these (http://www.active-robots.com/products/motorsandwheels/stepper-motors.shtml)