getting started with electronics?

Hey all.
I have finally decided to make me a RepRap, but just a few questions, I hope you can help me find answers to.

I'm going goning for the RAMPS, but i'm somewhat in doubt about what to choose Pololu A498 [www.pololu.com] or Pololu A4983 [www.pololu.com], to me, there seems to be no big difference, what shell I choose, is there a difference, and what is the impact?

stepper motor, I'm thining to uses NEMA 17, but what does, Full Step, Half Step, Sixteenth step, etc. mean, is it a thing the stepper motor must support, or is the motor driver that controls it?
what is Step angle, and what do you choose, and why? anything else I need to think about the stepper motor?


I'm just starts to build a small CNC too, and think that it can be converted into a repstrap. i have a couple of NEMA 23 Stepper, can they be, or are they too big for a Poloul? the steppers i have (PDF) --> [the-galaxy.dk]

I'm sorry for any spelling/typo, but I'm a little dyslexic

I am running Pololu A4983, A4988 and china made stepsticks A4988 on nema 17's and 23's and the drivers all seem to work the same.

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You want the A4988, but the specs look to be the same. A NEMA 17 will work fine, the number corresponds to the body size, so a NEMA 15 is a little smaller (and thus less powerful) than the 17. Each rotation that the motor goes through (say 1.8 degrees) can be broken down by the coils so 1/2 stepping would be .9 degrees, and 1/4 step would be .45 degrees, etc. I believe it is the board that determines the stepping? Not sure on that one. As for the NEMA 23's you have: They are rated at 2.8 Amps, but the pololus only do 2 amps, so your torque will be a little more then 1/4 less than the rating (assuming linear relation, might be logorythmic), regardless the motor is rated at well over required torque rating.

marnargulus Wrote:
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> so a NEMA 15 is a little smaller
> (and thus less powerful) than the 17.

Not always true. Check the motors specs to be sure.

When running in the same line of motors, the increase in number with correspond with the power of the motor. That being said, I can not ensure that a company will not ignore industry manufacturing specs. But when looking at a line of motors from Company A where they are all Model A in a Nema 15 Model A, Nema 17 Model A, Nema 23 Model A set they will increase as you increase the body size. If you get a NEMA 23 and it is less powerful than ANY NEMA 15 you got ripped off. If you get a 17 that is less powerful than the avg 15 you got ripped off. If you find a 15 that is way over spec for the same price, by all means grab it.

So, technically yes, you are correct. Thank you for being pedantic.

17 is best bet, 23 will work you just might need a slightly stronger stepper driver and might need to change the mounting brackets to accommodate.

4988's have some thermal protection and a couple other enhancements, it is a newer replacement for the 4983's I think.

4983's have the thermal protection as well.

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About a week ago, I asked myself the same question. What IS the difference? The spec sheets are almost exactly duplicates of one another BUT the functional block diagram for the 4988 shows two little boxes on the Gate Drive box labelled OCP where the attachment is to the final stage drive transistors. That led me to the table where its value is specified in a box that doesn't exist on the 4983's table.

Under Protection, the 4983 has four entries:

Quote

Thermal Shutdown Temperature TTSD – 165 – °C
Thermal Shutdown Hysteresis TTSDHYS – 15 – °C
VDD Undervoltage Lockout VDDUVLO VDD rising 2.7 2.8 2.9 V
VDD Undervoltage Hysteresis VDDUVLOHYS – 90 – mV

The 4988 has an addition:

Quote

Overcurrent Protection Threshold IOCPST 2.1 – – A

Then I noticed the titles of the two spec sheets:

Quote
A4983
DMOS Microstepping Driver with Translator

Quote
A4988
DMOS Microstepping Driver with Translator
And Overcurrent Protection

The difference is an Over Current Protection feature that the spec says has a minimum value of 2.1A.

For our use, on these little daughter boards, that is essentially NO difference.

Hi everyone,

I am allready having a few A4988's here and my Stepper-Motors. Unfortunately two of them seem to have not enough Torque. So I wanted to buy a stronger NEMA 17 Stepper, but I am not sure if I can use it. What specs does a Stepper need so it can be used?
A Stepper I wanted to buy has the following specs:

Frame Size: NEMA17
Step Angle: 1.8 degree
Voltage: 3.4V
Current: 1.7 A/phase
Resistance: 2.0 Ohm/phase
Inductance: 3.0 mH/phase
Holding torque: 3400g-cm 48OZ-IN
Rotor inertia: 54 g-cm2
Detent torque: 0.22 kg-cm
Number of wire leads: 4
Weight: 0.24 kg
Length: 40mm
Motor Shaft: 5mm

Can I use it?


Sublime Wrote:
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> I am running Pololu A4983, A4988 and china made
> stepsticks A4988 on nema 17's and 23's and the
> drivers all seem to work the same.

Quote

Unfortunately two of them seem to have not enough Torque

Did you adjust the current trimpot on the Pololus/StepSticks?

Quote

Can I use it?

Yes, but there are motors with more holding tourque, still rated below 2A. Make sure you have 4-wire types and a voltage well below the voltage you supply your Pololus with, which is usually 12V.

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If you have the time to wait China sells sets of 10 for 170 shipped (they will be labeled SAMPLE TEST EQUIPMENT or something like that) on Ebay. That is as good a price as you will get, as even the cheaper suppliers selling the NEMA 17 for 17 dollars add on a shipping cost of 10-15 dollars (and I think they get them from China anyway) Your country really dictates who will have the best power per dollar, as shipping is the major cost factor in these motors. (whereas something like a Step Stick from China costs the same as the stepper driver directly from Pololu)

Manargulus, I'm not sure about that being the best price. Last time I bought NEMA 17s from tony on ebay, it ended up costing me 7.5 euro per stepper, shipping included.
Not that, although they work fine, those are used parts.

Yeah, these are new motors, and a set of ten shipped usually costs more than 5.