Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: notgiven on July 21, 2011, 07:17:42 AM
-
I have 3 step motors here from automation direct that I intend to use with an Arduino Uno.
They're NEMA 23 and heres the link to the motor's page. Specs are on the top right of the page. (http://www.automationdirect.com/adc/Shopping/Catalog/Motion_Control/Stepper_Systems/Motors_-z-_Cables/STP-MTR-23055 (http://www.automationdirect.com/adc/Shopping/Catalog/Motion_Control/Stepper_Systems/Motors_-z-_Cables/STP-MTR-23055))
I dont know for sure what power supply to use. I've been looking around alot to try to get an answer but I'm still confused. If someone already covered this topic please link it to me, and sorry for being a nuisance...
Concerning the motors, I couldn't get the recommended power supply and driver (middle of the page, self-same link above).
However, the "Motor Torque vs Speed" charts that came with the motor give torque values for only 32-, 48-, and 70- volt power suppliers. Does this mean my steppers wont turn with a supply lower than 32?
I ask because I can easily get my hands on a couple of these 6 V "lanturn batteries" (possible even 12 V ones) to connect to the motor:
http://www.o-digital.com/uploads/2179/2182-1/Lantern_Battery_6V_4R25_2_320.jpg (http://www.o-digital.com/uploads/2179/2182-1/Lantern_Battery_6V_4R25_2_320.jpg)
Could a battery like this possibly supply enough power? Maybe if I hooked up 4 or 6 of them to get voltages of 24 or 36?
I tried to calculate a good voltage supply using a formula I found here http://www.geckodrive.com/ark-4/faq.html (http://www.geckodrive.com/ark-4/faq.html)
But no luck.
I goes
Drive Supply Voltage = 32 * vmH Inductance
Example of a motor with 4mH inductance:
32 * v4mH = 64VDC
I dont see how they got 64 V if its simply 32X4. I guess im missing something... Besides, with an inductance of 2.36 mH for my motor, 75.52 V seems a bit high.
So basically, Im asking how i might work my may up to these kinds of voltages (32, 48, 70) using other methods (possibly mutilating a phone charger or something?). I dont have a ready made driver board like what was recommended above (I was just gonna use a solderless breadboard and SN754410ne H-Bridge) and I think the ready-made ones have some "regulators" or something built in, so I dont know what kind of voltages are dangerous for my motors, or arduino, or myself.
If there's a method to figuring this out, could you also please enlighten me so I can spread the knowledge to other possible noobs.
Lastly, if speed vs torque is a factor in any of this, I just want to add that torque is more important to me than speed. I dont even know if these motors can move their own weight. 1.5 pounds is a little much...
Any input is greatly appreciated. Thanks in advance !
-
Hi,
I have 3 step motors here from automation direct that I intend to use with an Arduino Uno.
They're NEMA 23 and heres the link to the motor's page. <Snip>
NEMA-nn is just a form factor, you need to find the exact type number to be certain of what you have.
The datasheet lists 3 NEMA-23 units: 0.75 Ohm/2.8A/2.36mH, 1.1 Ohm/2.8A/3.82mH and 0.4 Ohm/5.6A/1.18mH.
Using Ohms Law you get: 0.75*2.8=2.1V, 1.1*2.8=3.08V and 0.4*5.6=2.24V.
That's what the mentioned models coils are rated for in these 3 motors. The inductance you only need for calculating max. stepping speed (it takes a finite time to get the energy into and out of the coil each step).
-
Thanks a lot for your help. One more issue and I think I'll be golden : do you think an SN754410ne H-Bridge can do current regulation so that my motor doesn't explode? Or could you point me i the direction where I could figure it out myself?
Thank you again.
-
Hi,
do you think an SN754410ne H-Bridge can do current regulation so that my motor doesn't explode?
SN754410 is a 1A max. driver, so that won't do at all.
Depending on which of the motors you have, your max current is either 2.8A or 5.6A
Besides that, any driver can be extended with current limiting.
Or could you point me i the direction where I could figure it out myself?
The datasheet is always the first place to start.
You can get integrated motor drivers that can handle the currents you need, but most come in SMD type packets (Polulu's got a 30A driver mounted on a PCB, so that would be easy to use) and you also have the option of building the driver from the ground up.
-
What happens to a step motor that is only supplied 1/3 of its rated current? Will it simply not move at all?
-
Hi,
What happens to a step motor that is only supplied 1/3 of its rated current? Will it simply not move at all?
It loses torque (big time) and if you try to go faster than painfully slow, it will loose steps for the same reason.