low torque

ok
i am using some Chinese stepper motor on my cnc mill with following specs
12v
0.3 a per phase
3100 g-cm torque

Using with a3982 same as stepper driver 1.2 . it got a pot but i dont know what to do with it. I am using 2 of them in full step as they have weird problem that when i give 5 v to there micro step pin from sanguino THEY GET REALLY HOT IN FLASH OF HALF SECOND. as soon as i turn on sanguino but no problem when i give ground. i can see the lights are dimmer on sanguino when i connect to a 5v, i like to run them on full step but i dont see the difference. Should i give power through 7805 from 12v or there is other problem as similar 3rd driver who got different cap between power supply work fine in both mode. I dont think its problem of that cap

My machine is not smooth, that i can understand, but one of my smoothest axis also stalling i cant get more then 150 mm/min at my 15tpi rods.
I am using a pc power supply.

what should i do to increase the speed because after that they stall , should i try more voltage ? Please help me understand stepper motor torque , current and voltage stuff

ps and the resistance per coil is 40 , which i think is high

You need to adjust the pot to a value where the motors work, but not too much to avoid them using lots of current. I've seen a number of people recommend half way, and then work from there.

Also, what is the max current of your power supply for the +12V line? It should be on a sticker somewhere on the supply.

You may be exceeding the max current of the supply (the dimming). You can test this if you have a multimeter, by disconnecting the +12v wire and putting the meter between the +12v wire and the +12v input on your electronics. Make sure you connect the leads to the Amp pin (usually separate from the other pins, and may have something like 10A written above it) and the Com pin. Don't worry if you get it backwards, as it'll just read negative.

Also: How many wires are on your stepper motors?

The more current you get through the coils, the more tourque you get. At 40 Ohms resistance, you get 12 V / 40 Ohm = 0.3 A, which isn't very much. Rasing this to 36 Volts (Pololus can deal with that), you'd get 0.9 A and about three times the tourque, but also a lot more heat, of course.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

its got 6 leads

the pc power supply is powerfull enough for these nema 17 motors,
which give more torque half or full
because with 15tpi the accuracy is not the issue
can i chain 2 power supplies to give 24 v i think a3982 can handle that
i will check current value
the thing is the stepper motors are knock off of these
[www.snasda.com]
the 47mm length model
See what help you can give

again thanks for helping me out

one more thing , is the torque to pps graph is more or less same shape if i changed it from half to full step or providing less volatge
i mean if a motor is giving highest torque at 500pps in half step and 36v will the max torque(offcourse less) at full step 12v will be at 500 pps ?

is 40 ohms resistance for a motor unusual. I cant deside that should i run these motors at 24 v. And the pot on driver is to limit current right?

In short what to do to get most from these motors.

PS how know from specs of motor that a3982 can drive it or not.I am a steeper newbie

Yes. 40 Ohms are more than usual in RepRap applications. And yes, the pot trimmer limits current. However, in your case there's nothing to limit.

That said, simply go ahead. Stepper drivers are the same for 40 Ohms motors as for 5 Ohms ones. If the motors work, fine, if not, nothing is lost.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

so to get more from motors i need to give more voltage because of resistance, and from spec, my driver is only at 0.3Amps ?

i have found a supplier near me

can you tell me which is the best motor. I am not building a mendel , i am making a cnc.
12V Pc power supply
a3982 driver

i need most torque that can be obtained with above spec

[sparkmotors.in]

That's a hybrid stepper motor. You want permanent magnet motors. With 200 or 400 steps per revolution, please. At least if you want to build a RepRap machine. A Mendel can do light milling, like mill diameter 2 mm, 1 mm deep in plastics. For CNCs capable of running a 10 mm mill bit or even milling metal, other rules apply, and other forums are better suited.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

reprap uses hybrid motor. All general motors are hybrid. Stick to metal to your mendel motor when turn off and tell me its is permanent magnet or not

karandex Wrote:
-------------------------------------------------------
> reprap uses hybrid motor. All general motors are
> hybrid. Stick to metal to your mendel motor when
> turn off and tell me its is permanent magnet or
> not

The rotor in the middle is a permanent magnet. The outer shell of the motor is the coils. They are most definitely permanent magnet motors. I have taken them apart before too...

Edit: It appears that hybrid steppers use permanent magnets, so hybrid steppers and permanent magnet steppers are not mutually exclusive.

Edited 1 time(s). Last edit at 03/01/2011 01:16PM by NewPerfection.

There are three types of stepper motor:
Variable reluctance.
Permanent magnet.
Hybrid.

Reprap uses Hybrid and yes they do contain permanent magnets but they also have pole pieces on the rotor as well as the stator, like VR, which is why they are called hybrid.

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[www.hydraraptor.blogspot.com]

nophead Wrote:
-------------------------------------------------------
> There are three types of stepper motor:
> Variable reluctance.
> Permanent magnet.
> Hybrid.
>
> Reprap uses Hybrid and yes they do contain
> permanent magnets but they also have pole pieces
> on the rotor as well as the stator, like VR, which
> is why they are called hybrid.

Good to know. I always learn something new from you

Edited 1 time(s). Last edit at 03/01/2011 05:02PM by NewPerfection.

i got new motors. these are nema 23 , with 2.6 ohms resistance, about 11Kg of torque. DOnt know other specs.

Now i tried these motor with a3982.When the pot is adjusted to 1.1Amps it start to get warm.After 1.2 the motor makes some plasma blaster charging noise. ( is this noise mention in stepper driver 2.3 instructions?) . I know a3982 cant drive these motors to fullest but atleast they are able driver it?

I am adding heatsink with fan, running on 12v, so can i use this config?

I honored that nophead answered in my topic.

PS if i increase voltage to 24 volt. Will motor heat up ? do i need to dial my pot way down ( i think current will increase) In short they will make things better or worse. Will torque incrase

Changing the voltage won't increase the current with the same pot setting. The motor won't get hotter either as the current is the same, and so is the torque.

The top speed will be higher as torque will fall off more slowly with speed. Also the on time of the chopper will be less, so you can probably increase the current further before the switching becomes audible. You can also fix that problem by changing the time constant resistor on the driver.

When you say "it get's warm" do you mean the motor or the driver? Both should get warm and can actually run quite hot when close to their full ratings. For example most stepper motors give the current rating that gives an 80C rise, which means they will run at 100C unless you add a heat sink.

I generally increase the current until either the motor, or the driver get just too hot to touch, i.e. about 50C. They are both then well within their specs. If you need more torque then add a heat sink and / or a fan to the driver. You should be able to get close to 2A then.

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[www.hydraraptor.blogspot.com]

So it is safe to use 24 v?
I will add heatsink.