Guidance/Recommendations for project using NEMA 17 stepper motors

Projects General Guidance
1

Hey guys! Been lurking for a few weeks, having fun learning and I'm about to take on a small project and was hoping to get some sage advice from you experts :slight_smile:

My project will use 2 NEMA 17 stepper motors. Link to them is here:
https://www.amazon.com/gp/product/B088NNB7BD/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

I have 2 options for power supplies on hand: (unless you recommend something else).
12v Battery pack (Amazon)

24v AC->DC 5A (Amazon)

I need first, recommendations on a good user friendly Stepper Motor driver. Being a n00b, I bought a couple L298N's to tinker with, and man, they get hot quick and have since learned they're not well suited for my application/hardware setup. So, please...anyone recommend a good one?

Secondly, and this may impact driver recommendations, but my project will ideally run both Steppers from a single Arduino Uno R3 (Elegoo). I want to have both steppers begin with push button and run to predetermined # of steps at a predetermined speed, at the same time. Once reaching the destination, they will automatically return to where they started and wait till I push the button again to have them repeat this process.

Lastly...which power supply I linked will be best or will both be acceptable? I'm really liking the 12v DC battery pack option for convenience of portability but if it's had to get decent speeds from 12v, I'll live with wired 24v.

Thanks in advance!!

Brian

2

12 volt will do unless You have really high demands on the stepper performance. Drop the L298. They might work for DC motors, not for steppers. You need a driver having current controll. The A4988 or bigger things are recommended.

3

3volt/2Amp tells me that this is a low-impedance 1.5ohm stepper.

If you use that with an L298 brushed DC motor driver, you will eventually fry the L298 and/or the stepper.
Must use a current controlled stepper driver.
2Amp is a bit much for the A4988. Better use something like the DRV8825.
Higher voltage basically means higher possible speed.

Stepper motors use full power all the time, so a poor choice for batteries.
Leo..

4

Steppers are a very poor choice for a battery powered project, especially those current hungry motors. For operation for any significant length of time, plan on using a big, lead acid battery.

The L298 driver is not a stepper motor driver and won't work at all with those motors.

If you do use the DRV8825 from Pololu, keep in mind that it can support at most 1.5 A per winding without extra cooling. You won't get the full, available motor torque.

With all stepper motor drivers, it is essential to set the current limit correctly.

5

Thanks guys!!! Learning a lot and having a blast doing so!! So, I just ordered the DRV8825 with heat sinks and some 4010 24v cooling fans, I'll throw one on the house that I eventually get around to whipping up in Fusion 360 and printing. Guess I'll go with the 24v AC->DC 5A power supply instead.

@jreminton When you say, set the current limit correctly...you mean like what this guy is doing here:

Thanks again everyone!!

Brian

6

Did you go to the DRV8825 page on the link I gave you.
All the important information is there, including setting the current.
Leo..

7

If you ordered a knockoff of the Pololu DRV8825 driver, their instructions on setting the current limit probably won't apply. The Vref setting depends on the value of the current sampling resistor.

8

If you need the full torque of the motors in the link in the Original Post then you will need a more powerful driver than a DRV8825. I suggest you get a driver that can provide at least 3 amps to give yourself some headroom. It is never a good idea to operate electronic equipment at its limit. Unfortunately more powerful drivers will be more expensive.

A laptop power supply can be an economical option. Many of them produce 17v or 19v DC at 5 or 6 amps.

...R
Stepper Motor Basics
Simple Stepper Code

9

@Wawa (Leo): I looked through the material there on the DRV8825 and watched the video tutorial on how to set the Vref, but ordered off of Amazon (Prime member so near instant gratification nearly always wins out on me :)) It's a brand called "HiLetgo" So, I'm sure they're a knock-off but I'm not really needing ton of torque or speed at this moment. Hopefully of the 5-pack that I ordered, at least 2 will work :stuck_out_tongue_closed_eyes:

@jremington: Good to know...if I can't find specific instructions on this mfg's version of the DRV8825, I'll pick a low value that should be safe. In the instructions on pololu's website, she indicated in her video that at full steps (what I'll be doing) only about 71% of the specified current will actually be applied...if I understood her at least. So, to me...that seems like it will provide me a margin of error/safety? Here's a link from the HiLetgo site about the driver with pictures...maybe a trained eye can tell what resistor it uses?

@Robin2: Shouldn't need full torque. The carriage this thing will move is on linear rails and is butter smooth w/o a payload in it and shouldn't have much in the form of resistance to overcome. BTW...loved your primer to stepper motors! Stumbled across them on a post on here a few weeks ago and was really helpful!!

10

How much mass will the motors be required to accelerate and decelerate without missing steps?

11

What drives your needs is your application.

A stepper driver has a natural voltage. This is the voltage that you can run the motor directly without over heating and without other damage. The nameplate on the motor lists that.

If you run the motor at that voltage as so many do, and you get the project to work as you need. then everything else is not only silly, but a waste. Lots of people use simple UNL2003 Darlington transistors. why ? because it is right for the application.

If your motors cannot power your device, you can add a chopper driver and set it properly with the sense resistors.
The L298 has sense resistor inputs like all stepper drivers.

As you said, it can get hot. yes, it uses transistors and not FET's so it has a very measurable voltage drop. (upwards of 3 volts YIKES ! ) in electronics, when you consume power, you get heat. so the L298 is not very efficient and it does require heat sinks if you use sense resistors that allow it to run up to it's maximum. ok, horribly inefficient compared to FET based stepper drivers.

Also, about 98% of L298 modules sold, short out the sense inputs turning them into a motor driver and not a stepper driver. Only a few modules have either pots or resistors to run it as a true stepper driver.

When you double the nameplate voltage, you can get double the power out of the motor. And the motor will get hotter as you increase voltage. Add more voltage and you get more power and more heat.

I probably don't need to tell you that using a high power transformer so you can run your steppers really hot is exciting, but.... if you only need 5 volts to get all the power needed for your application, then every volt over what the application requires is total waste.

So, the first step, would be to lower the voltage until the motors started to miss steps. then add some value, 20% more voltage ? and test, increment until you are satisfied that your motors do not miss steps.

as was noted, steppers consume full power at rest and while running, so are horribly battery UN-friendly.
but, if you only need to run them occasionally, you can just turn off the power.

Again, application. without power it will not hold position... unless your application does not need the motor to hold position. Lots of applications do not require active holding.
The other concern is missed steps when the power is off. again, a simple end-switch makes that issue disappear.

So, before getting down the road too far, have you run your steppers at their rated voltage and tested them on the application at hand ?

12

dave-in-nj:
So, before getting down the road too far, have you run your steppers at their rated voltage and tested them on the application at hand ?

Sorry, but I disagree strongly.

There are some stepper motors with high-resistance coils that have a 12v nameplate voltage - I have some myself. However most stepper motors have nameplate voltages of the order of 3v (as is the case of the OP's motor) and nobody ever runs those stepper motors at their name-plate voltage. Indeed most stepper motor drivers need a minimum voltage that is well in excess of the nameplate voltage. Stepper motors are current-driven devices. And their torque falls off rapidly as speed increases. A higher voltage power supply (within the limits of the driver) will give more torque at higher speeds - but then it is essential to have a specialised stepper motor driver that can limit the current to protect the motor.

...R

PS ... I control my 12v steppers with A4988 drivers and power them with an 18v laptop power supply.

13

Robin2:
Sorry, but I disagree strongly.

There are some stepper motors with high-resistance coils that have a 12v nameplate voltage - I have some myself. However most stepper motors have nameplate voltages of the order of 3v (as is the case of the OP's motor) and nobody ever runs those stepper motors at their name-plate voltage. Indeed most stepper motor drivers need a minimum voltage that is well in excess of the nameplate voltage. Stepper motors are current-driven devices. And their torque falls off rapidly as speed increases. A higher voltage power supply (within the limits of the driver) will give more torque at higher speeds - but then it is essential to have a specialised stepper motor driver that can limit the current to protect the motor.

...R

PS ... I control my 12v steppers with A4988 drivers and power them with an 18v laptop power supply.

I think that is the first time I have ever heard anyone say that if it works, then it is not acceptable.

As for your misunderstanding of motors, I would invite you to read the thread on kinetic sculptures. Some people are running scores (that is in multiple of 20) steppers at nameplate with the UNL2003 or similar non-chopper transistor drivers. In fact, before chopper drivers became common, it was practically unheard of to run steppers at anything other than nameplate in the hobby world.
[ edit : you might need to go back to the Basic-Stamp forums about steppers. chopper drivers were said to be too expensive and not offer any benefits for the applications ]

If you think of a stepper like a voltage regulator, every volt on the supply side, over that which is required, is burned as heat, you would understand that every volt over that which is needed for the application is wasted.

I think it is a fundamental rule in engineering that the application drives the design.

And I am well aware that if your stepper required 7 volts and your choice was a 5 or 12v power supply, you would use the 12v every time and live with the wasted heat.

But at the same time, we should not be cobbling together circuits to make the parts work in that circuit, we should be making circuits that make the device work properly in the application.

So, before we confuse the OP any further, maybe we should ask what the project is, how well it worked with the L298 (not how hot the chip got, but how well the project worked)

How many minutes a day it is supposed to work, and then offer solutions based on the application.

14

dave-in-nj:
with the UNL2003 or similar non-chopper transistor drivers.

The ULN2003 is normally used with 28BYJ-48 stepper motors. That is not what the OP has.

...R

15

Those knock-off Hiletgo DRV8825 drivers worked great!! I set the vref to a safe 900 (only full stepping and uses 71% only on full step) Wired them to the motors and butter smooth!! I then connected my multimeter in series with one of the coils to see what amperage I was actually pulling and sure enough was just about a single Amp! So then I tuned them up to a comfortable 1.4 Amp. Safely under both the steppers rated limit and the drivers. When connected to the battery pack at 12v, I think it runs the smoothest. The 24v AC->DC was louder and seemed more "choppy". I'm happy with the outcome!

So, THANK YOU ALL for your invaluable guidance!! You guys all rock!!

One final question...I'm designing the control box for the electronics. Since I can use the battery pack perfectly, I'm wanting to make this modular as possible, so I'm looking for suggestions for some sort of 4 prong connector that lends itself to being mounted into project box (I'll CAD and 3D print it, so I can make any size opening I want/need to in it). I'm wanting to be able to plug the wires from the stepper's into the project box with all the electronics and control knobs (pento's and push buttons) So, hoping there's a good suggestion on some sort of 4 wire plug that I can mount into the side of this box, then just plug them in when I'm ready to power up and go. Anyone have a suggestion? For that matter, could be an 8 wire one and simultaneously plug both in. Wouldn't have to be 2 at 4 wires each I suppose.

TIA, and truly, you guys are amazing! I'd buy you all a beer if you lived in Louisville!! :smiley: