2x Stepper Motion control

Hi Guys.

I'm really new in electronics, but im working on an important project to me. However, im really not sure about its possibilities. I would like to use an arduino nano with two sparkfun easydrivers, each would drive a 28mm stepper motor. EKP28HS32-067S4

28mm Stepper motors

Would the system run on 7.2V nicely?
If i run the motor on 7.2V, i would get 8.12 revolutions/sec at maximum speed. Am i right with that?
I also cant figure out, how powerful would it be, if it's output is a wheel with a radius of 2mm? Does that mean, that it moves 12.x mm multiplied by 8.12 times in one second? If so, how much weight could it handle? I would be really thankful if someone could help me with some guide, at least where to start.

An EasyDriver can only provide 750mA. It should be suitable for the -067S4 motor as it seems to require 670mA.

That motor has a coil resistance of 5.6ohms and with 0.67A that gives a nominal voltage of 3.75v. It should work OK with 7.2v but for higher speeds a higher voltage (up to the max of the EasyDriver) would be better. You MUST adjust the Easydriver so it only allows 670mA through the motor.

I have no idea where you got the numbers 8.12 rps or 2mm.

For 8rps there would be 1600 steps per second (at 200 steps per revolution). That is a high speed, but might be achievable. I suspect you would need a higher voltage.

The holding torque is stated as 600gm at 1cm radius. That will only be achieved at full current (670mA) while the motor is stationary. The torque will fall of as the motor speed increases. Some manufacturers provide a graph showing how torque varies with speed.

Rather than ask "how much could it handle" you should start at the other end. What do you want to do and what torque at what speed does that require. Then you can go looking for a suitable motor and motor driver.

...R

There is no reliable way to calculate the performance of a stepper (unlike
for normal DC motors), due to the failure mode being miss-stepping which
is strongly dependent on mechanical resonance, mechanical load and inertia
as well as supply voltage, current drive and microstepping scheme.

Hey guys, thanks for the quick replies. Ye, i was quite sure, that i was lost about these data. I did some calculations with this (Stepper Motor Maximum Speed and Power Calculator) calculator, but probably did not put the correct values.

Anyway. I would like to move a maximum 3kg heavy object on wheels, with a maximum speed of around 80-100mm/sec, and minimum speed around 2-3mm/s. - If possible.

"The holding torque is stated as 600gm at 1cm radius." Does that mean, that the leadscrew's radius is 1cm? Or am i getting it totally wrong? So if, then in case the radius of my wheel is - for example - 2mm, i get roughly 5 times more holding torque? So then that holding torque is around 3000g? That would be quite perfect for me.

For batteries, i would use two of 2200mah Li-Pol battery. They work on 7.2V, but i heard that i might could combine them, then i could get 12V. Im sure it would not last for too long, especially in this case, but i might dont need very long time, and its a worth for the mobility. I mean mobility is a main point too in this project, surely in a realist way.

You are still a long way from figuring out your requirements.

Can you build a mock-up of the heavy object on wheels and measure how much force is needed to move it at different speeds. This will depend on the smoothness of the surface, the friction in the tyres, the friction in the bearings and whether the surface is level. You just can't guess it - apart from grossly over-specifying the motor or being content to replace a small motor with a bigger one until you get it to work.

The next problem is that you need to read up about torque. There are plenty of on line resources. I am not going to repeat them.

Where did you get the idea of a "leadscrew"
Which reminds me that you did not answer my earlier question about where you got the numbers 8.12rps and 2mm

Worry about batteries AFTER you have figured out this stuff.

...R

Hi Robin2, thanks for your time.

Well, i was just reading around in forums, searching for how strong stepper do i need. And then i found this topic (http://www.cnczone.com/forums/linear-and-rotary-motion/20463-cnc.html), but as u said, its going to be more difficult than this.

I did answer ur question, i got the 8.12rps from the link (Stepper Motor Maximum Speed and Power Calculator) above, but as i said, i probably did not put right values into this. Or its not working anyway. Sorry. I got the two mm radius from that... A 2mm radius wheel would move around 12mm each rotation, so with 8.12rps, its around 100mm. But since you say its false, im just saying.. that was my logic.

A nema17 motor should be okay anyways, but that will surely need 12v, right?

when using a stepper you work it out backwards what you a moving first then everything else.

look up a stepper torque calculator and compare it to what the stepper you have can do.

if you don't know a lot about motors you need the graph for the stepper

Szaboo:
A nema17 motor should be okay anyways, but that will surely need 12v, right?

More reading, methinks

Nema 17 defines the size of the front face of the motor. It says nothing about the capabilities of the motor.
Stepper motors should normally be driven with the highest voltage possible that is compatible with the stepper motor driver.

A 2mm radius wheel is tiny. Are you sure you have not made a mistake by a factor of 10 or 100 ?

...R