Salvaged Stepper Motor Blues

Question

So recently my company threw away some rather large and reasonably old laser printers. One was a LaserJet 9050dn the other was a Epson printer/scanner combination. Being a little industrial I thought let me salvage them and brought them home.

I managed to salvage a couple of stepper motors. However I am having huge trouble is getting them to step properly. So lets get into the details.

Components used:

• 1x Freetronics eleven (Arduino Uno compatbile)
• 1X H-Bridge driver shield(Freetronics rated for 40V/2A max).
• 1X Old scanner power supply which has a output of 24V/2A.

Currently there are two stepper motors I am interested in using. They have the following part numbers:

• 1X MITSUMI M42SP-4N
• 1X Minebea-Matshushita 17PM-J212-G2ST

Just to keep this short I am going to focus on the Minebea-Matshushita 17PM-J212-G2ST. I have been unable to find exact matches on these serial numbers when looking for datasheets but I have managed to find the following sheets on the net.

1. Minebea-Matshushita 17PM-K datasheets found from Minebea. However I cant match the model exactly.
2. Minebea Stepper Motor Information & Specifications also carries some useful information.

So it appears that these are 24V steppers(in both cases). The Minebea-Matshushita 17PM-J212-G2ST appears to have a step angle of 1.8 degrees which should give me 200 steps per revolution. I have not been able to find the current needed to drive this motor but judging by the looks of things it will be between 0.8A and 1.2A.

I then used my multimeter to find the pairs of wires. It has 4 wires coming out (Bipolar motor I guess). The colours of the wires are red, yellow,orange and blue. First pair was red and yellow with red being positive/anode. Second pair orange blue with orange positive/anode side.

I wired my power supply into my h-bridge and started using the recipe and quickstart found at the freetonics site. This is where the frustration begins. When asking the motor to do one complete revolution(360 degrees) it does more than 360 degrees at times and other times it does less. I tied a cable tie to the motor so I can confirm it.

So I tried the one-step-at a time sketch to see if I can troubleshoot it. Here is what I have noticed. The steps are mostly correct one step at a time clockwise however every now and again it will jump counter clock wise and then clock wise again. I suppose you can call it a jitter.

Interestingly both these motor show the same behaviour pretty good step action just every 25 degrees or so a jitter. So I suspect that this might not be bi-polar motors but uni-polar? This blog entry points me to believe that this might be the case. However the datasheet in this case points to a M42SP-7.

So my question would be simple how do I figure out if they are bi-polar or uni-polar?

Can someone help me with a proper datasheet?

Any tips would be really appreciated.

Update:

Note that I can get both motors to step clock-wise and counter clock-wise I just cant get them to do a whole 360 degrees without a jitter. Based on the Wiring Mitsumi stepper ( M42sp-4np) with arduino blog it appears that the Mitsumi is a uni-polar motor with a 2-2 phase excitation. What stumps me is that the wires are paired thus it must be bi-polar?

So last night I tried 2-2 phase excitation with the MITSUMI M42SP-4N and it appears to be solve the problem with this motor in particular. From early observations the motor now steps without jitter, however it was late so I will need to confirm this.

I was previously using 1-1 phase excitation i.e.

Step number: 1a 1b 2a 2b
1            1  0  0  0  
2            0  0  1  0  
3            0  1  0  0  
4            0  0  0  1 
5            1  0  0  0

When using 2-2 phase excitation I get a more steady step however this needs to be confirmed a bit more:

Step number   1a 1b 2a 2b
1             1  0  0  1
2             1  0  1  0
3             0  1  1  0
4             0  1  0  1
5             1  0  0  1

Just some added observations. The headache continues but I am learning a LOT about steppers motors.

Update:

Not a 2-2 phase excitation these are definitely bi-polar. I am currently watching the Minebea-Matshushita 17PM-J212-G2ST do 360 degrees both clock and counter-clockwise. I hooked them up to a 12V/1A power supply both motors are running smoother and cooler and stepping relatively jitter free. I suspect the whole issue is a lack of a proper data-sheet.

Will update as things progress and once solved add pictures and sketches so the next lucky sod wont loose as much hair as me.

Update:

Thanks to Chris who made me look at the sketch in detail again. These motors seem to have a minimum rpm of sorts. I was trying to go for a really slow rpm under 5rpm at this speed these motors show the jitter effect. However when moving the speed to 10rpm and up no jitter.

Answer 1

Keeping this here for future reference. It appears these motors have a minimum RPM of sorts and running them on a lower RPM causes the jitter effect described above.

Like I mentioned in the updates when running at 10RPM or above these motors seem to perform very nicely.

Update: I recently bought a ADAFruit motorshield and I am getting much more stable results with this shield and the stepper motors. I am even running them off 6V and they are working perfectly even at lower rpm.