Cheap unipolar NEMA 17 motors in Québec
June 15, 2012 12:08PM
I'm not sure if this is the right forum to post this, move it to a more appropriate one if needed. I can't seem to find a "good deals" forums.


[www.acceselectronique.ca] currently has this motor in stock in all four physical locations, however it's not in their website inventory:

Japan Servo Co. Ltd.
KP4M2-008
1.8 deg/step
5 wires (unipolar)

I can't seem to find a datasheet for these, but they're only 4$CAD. I asked about the inventory and most stores had at least 50, some nearly over 400 in stock.

Be warned, however. Check each motor by hand to "feel" the steps of the motors. A lot of the motors I tested had almost no "step" in their spin, others almost felt like they had loose parts or debris inside preventing the motor to spin smoothly/correctly. After about 15 minutes of testing I was able to find what I think are four good motors with identical torque.

edit: I found a datasheet for KP4M2-203, those are 12V motors but the coils of the motors I bought (KP4M2-008) are 75 ohms (coil-to-common) instead of the 37.5 ohms listed in the datasheet.

May not be good enough for a RepRap according to some, but could still be quite useful for other CNC projects, especially at that price, size and 1.8 deg/step.

Edited 1 time(s). Last edit at 06/15/2012 03:20PM by Yvan256.
Yes these motors are cheap, small, light, have a small T2 drive gear and a single 16mm (L) x 5mm(dia.) shaft. The only problem with them is that they are unipolar 5 wire version with four 75 ohm coils. I noticed that there are two type of these motors. The 260 g and the 180 g versions. They can be identified by of course there weight but also by their look, the lighter version having an aluminium cast casing.
I opened both of these and noticed that the lighter one has 8 coils and the other one has 4. Both motors can be rewired back to 2 phase easily.
I plan to use the lighter one for my extruder because it's small and light.
I also noticed that the lighter 8 coil version has a lower final impedance of about 15 ohms so I probably overlooked that they had and initial impedance that was different from the 4 coil version.
Once finished the 4 coil version was now 2 phase and has a 37.5 ohm per phase impedance. The finished 8 coil version has, as previously mentioned, a 15 ohm per phase impedance.
I tested both version with a pololu A4988 and both turned smoothly but the lighter motor heated somewhat after a short time at 25% setting on the current trim at 12Volts.
I'm making a series of images detailing the conversion process.

RJ
Re: Cheap unipolar NEMA 17 motors in Québec
March 18, 2013 11:52PM
AreJay Wrote:
-------------------------------------------------------
> I'm making a series of images detailing the
> conversion process.
>
> RJ

Is there a new thread for that?
Re: Cheap unipolar NEMA 17 motors in Québec
March 30, 2013 04:05AM
WOW that is really very nice price !


______________________________________
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Re: Cheap unipolar NEMA 17 motors in Québec
May 10, 2013 12:27PM
I actually bought 5 Japan servo co. NEMA17 steppers for my build. They are KH42JM2B-140G. They say on them DC5. 16V 1.2A 1.8degree /step. After getting the printer fired up, everything seems to work, however I'm just not so sure how fast everything is supposed to move. I'm using an ATX 300w psu, only connected the 5A 12v to my RAMPS.

The motors do get pretty warm only after maybe 5min of testing in pronterface. Should I be worried that these are 16v steppers? Anyone know if there's a way to compensate? After actually finishing my reprap I read its recommended to use 3.5v steppers. Of rather not buy new steppers right now maybe later on when I get some cash flow, but for now I hope I can use these.


-------
Makerfarm Prusa 10" i3V | Ramps 1.4 | Pololu A4988 | Hexagon | Marlin 1.0.2 | Autolevel
Printrbot Simple Maker 1405 - Sold
RepRap Prusa i2 - Decommissioned
Re: Cheap unipolar NEMA 17 motors in Québec
February 27, 2014 05:58PM
I Bough one of these motors KP4M2-008 to make tests on my makerfarm prusa i3. If it worked, I would buy some more, for my next machine... Finally I found the way how to plug those 5 wires stepper motor into a 4 wires ramps 1.4. but it is not strong enough. (I expected it beacause it is way smaller!) I tried it on my y axis. It looks like working well, but as soon as something goes against the movement of the heatbed, it jumps and the print is like crap. It might be strong enough for the z axis or the extruder I don't know. I also wonder if it is possible to raise the amps to make it stronger?

Here is the procedure I've done.

1.First, open the motor. You will see that all the colored wires are pluged into a white rubber pipe to protect form shortcut. All wires are plugged to a little copper varnished wire exept the black one wich has 4.

2.Pull on the black one out the white pipe and cut the 4 little wires, than use sand paper to remove 1/4in of varnish at the end.

3.Use a ohmmeter to find the pairs of wires making a coil. Plug one side of your ohmmeter on one wire and try the 4 little ones to find wich of these fits with the this one. Use something to note youre results, and do the same with the 3 other wires colors. It should give you around 75 ohms.

4. Then I went like try and MISTAKES, but I finally found it...

The four little copper wires must be plugged and soldered with tin into 2 pairs. The one corresponding with the white plugs with the one coresponding with the green, and the one corresponding with the red plugs with the one corresponding with the brown. and put some electical tape.

5. Close your stepping motor making sure every wires is on the sides and the shaft turns freely.

Now you have a 4 wires stepper motor

You can use some other tuto to find how to plug it into your ramps, but

Here are my results: the way i pluged the 4 other wires

ramps. stepper optionnal: (my maker farm color code)
2b--------green------blue
2a--------white-------yellow
1a--------brown------green
1b--------red----------red[/s]

Sorry for my english mistakes, I used to speak french...

Pis on est là à tout écrire en anglais alors qu'on dirait qu'il y a juste chez accès électronique qu'on trouve ces moteurs!

Edited 1 time(s). Last edit at 02/27/2014 06:02PM by jlguil.
Re: Cheap unipolar NEMA 17 motors in Québec
March 03, 2014 02:36PM
Me again...

I found an other way to plug the wires of this stepper motor, and like this, theorically, it is 4 times stronger. In fact, I have no way to test it but it is way stronger.

Ok, basically in the previous message, I did put 2 coils serial way. Wich adds the resistance. So instead of 70 ohm, I had 140 ohm.

I had the idea of plugging them parrallel way. This way The resistance is divided by 2, So instead of 70 ohm, I now have 35 ohm.

So if the resistance is twice lower, the amperage should be the double! makes a difference of a factor 4.

Right now I'm printing with one of them on my 7 axix and il works perfectly. (but is a little noisyer)

So the new way to plug them

I copied the procedure modifying the way to plug the wires...

1.First, open the motor. You will see that all the colored wires are pluged into a white rubber pipe to protect form shortcut. All wires are plugged to a little copper varnished wire exept the black one wich has 4.

2.Pull on the black one out the white pipe and cut the 4 little wires, than use sand paper to remove 1/4in of varnish at the end.

3.Use a ohmmeter to find the pairs of wires making a coil. Plug one side of your ohmmeter on one wire and try the 4 little ones to find wich of these fits with the this one. Use something to note youre results, and do the same with the 3 other wires colors. It should give you around 75 ohms.

Then,
plug the one that fitted with the white with the original green.
Plug the one that fitted with the green with the original White.
Plug the one that fitted with the brown with the original Red
Plug the one that fitted with the Red with the original Brown

Then plug them to your ramps`

Ramps stepper motor wire optionnal, my makerfarm color code
2b--------original green (+ fitted white)--------blue
2a--------original white (+ fitted green)(-------yellow
1a--------original brown (+ fitted red)----------green
1b--------original red (+ fitted brown)----------red[/s]

And then close your motor and plug it to your reprap.

Also, On the stepper motor driver, you have a screw, turn it clockwise to increase the strengh of the motor.

Like this you can use those 4$ motors on a reprap! And for my self, I will!

C'est vraiment pas cher!
Re: Cheap unipolar NEMA 17 motors in Québec
March 28, 2014 03:58PM
Merci pour les informations jlguil, je vais essayer de modifier un de mes moteurs en fin de semaine pour le tester avec mon contrôleur bipolaire.

edit: j'ai bloqué à la 2e étape car je ne trouve plus mon multimètre. confused smiley

Edited 1 time(s). Last edit at 03/29/2014 05:47PM by Yvan256.
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