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1  Using Arduino / Programming Questions / Re: Just got MINI steppers! What kind of code do I need to do PWM? on: July 10, 2013, 10:27:05 am
Ok, Got some Torque measurements done. This were measured with just one coil energized. The first picture shows the test setup. The motor is held by a parallel clamp. A small piece of wood was glued (CA) to the gear with holes drilled (0.02in) 35mm from the shaft center. This distance is the 'arm' for the torque calc. Pieces of resistor leads were put through the hole and form a loop to hang weight.
The weight is small pieces of solder.
The green board to the left is a stop to not allow the weight to hit the table when the motor is not energized. The picture show the motor energized, lifting the weight.

Small pieces of solder were added one at a time and the motor energized until it would not lift the weight. Then the last piece of solder removed the and remainder weighted on a precision balance.
The weight times the arm length equals the torque in gram-centimeter then converted to milliNewton-meter.

Coil Volt  coil I (Amp)     Torque (gm-cm)  (mN-m)
2.7          0.067               1.02                 0.10               
3.0          0.073               1.25                 0.12               
3.6          0.088               1.47                 0.14
4.7          0.110               2.04                 0.20       
6.3          0.145               2.4                   0.24

At 4.7V the motor does get very warm if not mounted but only slightly warm if mounted. The mounting does help in heat sinking the motor and if higher torque is required this should be a consideration.
At 3V the motor only get slightly warm.
As expected the Torque to linearly proportional to the coil current. Also, this steppers would work well at 2.7 to 3.6V and the H-bridge drive could be powered from a single LiPo battery. smiley
2  Using Arduino / Programming Questions / Re: Just got MINI steppers! What kind of code do I need to do PWM? on: July 07, 2013, 07:19:32 pm
TONS more info on the mini steppers for all who have them so far (or any who want some)!

Got to play with the stepper last night. I did break off the terminals of one after I soldered on 26ga wire. This wire was just too stiff for those tiny terminals. I was successful using 34ga enamel wire.

Some physical measurements first (note that these may not be exact, I used a dial caliber then assumed a nominal metric dimension).
The screw mounting hole has an M1.4 x 0.2 thread that is 0.030in (0.76mm) deep.
The gear is 8 teeth, Mod 0.25
Shaft diameter is 0.030in (0.762mm).

Now for the preliminary electrical.
I used my PIC16F84 controlling an Allego A3966 driver chip.
Vbb to the H-bridge FETs is 10V.

Now, a motor runs by the magnetic field and the field generated by a coil is dependent only on the current through the coil (B = m * i *n where i = current, n = number of turns, m = physics constant).
So, at DC (stepper holding a position) Ohm's Law holds for the current verse Voltage. These steppers coil R = ~38Ohm. Using this if the Voltage is larger than the current desired in the coil a series resistor can be used to decrease the current. The series resistor is one part of a resistive Voltage divider with the Coil's R as the other part. The calculation is: Vcoil = Idesired * Rcoil, Rseries = Rcoil *(Vsource - Vcoil)/Vcoil.

Since my H-bridge is powered at 10V and an earlier post said the steppers got hot at 7V and applying 5V directly to the stepper seemed to produce reasonable torque I calculated what the current would be at different Voltages and then what series resistor would be needed for a 10V source. These are:
@10V, 254mA, 0 Ohm
@7V, 182mA, 13.5 Ohm
@6.6V, 166mA, 22 Ohm
@5V, 131mA, 38 Ohm
@3V, 80mA, 87.5 Ohm

I have a bag of 22 Ohm resistors so place one in series with each coil and connected to the A3966 driver outputs. Applied powered to the PIC and driver. The PIC code starts sequencing the driver with half-steps (8 in the sequence) at a slow speed then gradually increases the stepping speed. The tiny stepper motor ran fine. After a minute of running the stepper's case was warm but not hot to the touch. By applying pressure the the gear with my finger the stepper could be stopped but the torque seemed to be rather strong for such a small motor.

Next is to build an apparatus to measure the torque output. This is difficult with a DC motor because to always has a continuous rotation. With a stepper one can measure the torque of one step.
My idea is to attach an arm to the output gear this is centered to have equal length, thus equal mass, of each side. With the stepper's shaft horizontal this arm is balanced and does not apply any torque to the shaft. Now add a weight (mass) at a know distance from the canter of the shaft. The torque this applies is easily calculated. Now apply power to a coil an see if it can lift the weight. If it can then increase the weight until it can not. The greatest weight it can lift is the Maximum torque.

Repeat but apply power to two coils.
Repeat but keep power applied to measure the holding torque.

Another test is to see how fast this motor will run (this may be driver and not motor dependent). I will also take a stepper into work and measure the Inductance of the coils.

Stay tuned for more.
3  Using Arduino / General Electronics / Re: It's time to play name that effect! C'mon down! on: July 04, 2013, 09:42:01 pm
Rob, glad that you got them. Here is ALL the info you need on them that another smart fellow who received these figured out. Have fun!

http://www.societyofrobots.com/robotforum/index.php?topic=17008.0
4  Using Arduino / Programming Questions / Re: Just got MINI steppers! What kind of code do I need to do PWM? on: July 04, 2013, 12:19:01 pm
@TerryKing; have you had a chance to mess with your steppers any?
5  Using Arduino / Programming Questions / Re: Just got MINI steppers! What kind of code do I need to do PWM? on: July 04, 2013, 09:47:44 am
UPDATE!!! smiley-lol
Waltr, over at the Society Of Robots forum has received his steppers and has done ALL of the research to figure out the specs on these Mini Steppers and it is posted here;

http://www.societyofrobots.com/robotforum/index.php?topic=17008.0

Now that all the head scratching is out of the way, we can get to the fun stuff! smiley-grin
6  Using Arduino / Programming Questions / Re: Just got MINI steppers! What kind of code do I need to do PWM? on: June 20, 2013, 07:47:06 pm
Just got motor driver chips SO SMALL that I have no clue how to even solder them, any clues?

http://s1362.photobucket.com/user/420photo420/media/20130619_164633_zps5ba3ca16.jpg.html?sort=3&o=0

http://s1362.photobucket.com/user/420photo420/media/20130619_164751_zps55c84154.jpg.html?sort=3&o=2

Thanks!
7  Using Arduino / Programming Questions / Re: Just got MINI steppers! What kind of code do I need to do PWM? on: June 20, 2013, 07:43:11 pm
Just got this information from a fellow I shipped them to.
Hi Stephen,
I received the stepper yesterday and I have done done some preliminary
testing on then. I have a manual step controller. It's nothing but a
bunch or switches that switch in polarities to simulate stepping. I
started using 5 v and then pushed it up to 7 v. With continuous
current on the coils the stepper started to heat up noticably. I found
at this  voltage the current was 153 ma @ 7v. The steppers have an 8
step per revolution. I think this can be refined using half steps and
a dedicated controller chip. I'll be looking into that. Soldering a
lead to the post is something that you have to be quick and use a very
small iron. The plastic case for the post will melt in a heart beat! I
do not have anything definite on the torgue yet as the controller chip
when I find it and get it hooked up will answer this more directly. So
far the steppers seem well made and work consistently with the
primitive setup that I used to make the steps.
Again the controller chip is what I need to look into next. I will
keep you informed. I would be interested in ordering more in the near
future after I get a controller chip connected.
8  Using Arduino / General Electronics / Re: It's time to play name that effect! C'mon down! on: June 11, 2013, 05:07:06 pm
Not a problem, even better in fact! Giving some cool widgets to a guy in the Netherlands is WAY more interesting then giving some to my neighbor (he prefers Whisky anyways smiley-wink)
it will be shipped tomorrow!

@MarkT; good looking out with more info on the subject, you came in a solid second  smiley-wink (better luck next time)

Heads up boys and girls, 'cause the next time we play, it will be on Inductance/resonance, and it will be for.....A NEW CAR! (<-- a lie smiley-twist) so study up! lol
9  Using Arduino / General Electronics / Re: It's time to play name that effect! C'mon down! on: June 11, 2013, 03:56:42 pm
DING DING DING DING We have a winner!!!! Get robtillaart a cigar! (and some stepper motors!) To claim your prize, PM me with your address and I will send 'em (Just got back from mailing Terry some). No Spam or any other BS. Just screwing around on the forum for a little fun. Next time will be a harder one! steve
10  Using Arduino / General Electronics / Re: It's time to play name that effect! C'mon down! on: June 11, 2013, 03:50:39 pm
@sampson jr; Yup (damn good to guess it with no video, gona have to pick a hard one next time!), by Feriday 1812. BUT, what is the force at work are right angles?
11  Using Arduino / Programming Questions / Re: Just got MINI steppers! What kind of code do I need to do PWM? on: June 11, 2013, 03:42:53 pm
38 OHMs each, where does that leave me?
12  Using Arduino / General Electronics / Re: It's time to play name that effect! C'mon down! on: June 11, 2013, 03:30:13 pm
What video?  Link broken? Private?

Should work now.
http://s1362.photobucket.com/user/420photo420/media/20130610_204014_zps25efd443.mp4.html?sort=3&o=5

Were you able to see the pic of those awesome mini steppers I have? Sorry bout that, might make this a semi-regular game, but it is no fun with broken links! lol Thanks, let me know. Steve
13  Using Arduino / General Electronics / Re: It's time to play name that effect! C'mon down! on: June 11, 2013, 03:26:31 pm
That is a link to photobucket, should be public, checking now.
14  Using Arduino / General Electronics / It's time to play name that effect! C'mon down! on: June 11, 2013, 02:33:01 pm
Time to bring some excitement to the forum today! SOOOOOOOO, Who can name (and half ass explain) the force that acts at right angles in this video?......
http://s1362.photobucket.com/user/420photo420/media/20130610_204014_zps25efd443.mp4.html


First one to get it right will get 3 of these MINI steppers mailed to them for free!
http://s1362.photobucket.com/user/420photo420/media/20130610_152133_zps7b6ec755.jpg.html

The game starts......NOW!
Steve
15  Using Arduino / Programming Questions / Re: Just got MINI steppers! What kind of code do I need to do PWM? on: June 11, 2013, 02:27:21 pm
I get them from a company in China that "re-claims" electronics from "scrap" that they buy at auctions. The result is cool stuff like this that is hard (or impossible) to find for a good price, BUT, that comes from god knows what, is in limited supply, and has no data sheet. Everyone that has PMed me so far has had at least one extra stepper thrown in free, for experimentation (otherwise known as frying it till the magic White smoke comes out!). I think that it would be cool to see an Arduino Mini creeping along with 2-4 of these under it, or diy clocks, ORRRR!! smiley-grin? I have a good amount of them still (that company does not DO small orders) so plenty to go around while they last! PM me. Steve
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