[cpr]

SOLVED: Sorry! There are potis on those Pololu drivers! To regulate the current! *triplefacepalm*


I am new to electronics and I just picked up again my "Shapeoko-clone" project I started last winter.
Could someone explain to me stepper motor behaviour?

I have:
- 1 "GAUPS Arduino-compatible Stepper Shield kit" GAUPS Arduino-compatible Stepper Shield kit - Amber Spyglass Ltd - (Powered by CubeCart)
- 4 "Pololu A4988"
- 1 power supply 24V 17A 400W Nunus Netzteil 24V 17A 400W f
- shielded cable Ölflex Classic 110 CY 4x0,75 4G0,75 http://products.lappgroup.com/online...ol-cables.html
- SM42HT47-1684B NEMA 17 stepper motors NEMA 17 Schrittmotor | aktive | Elektronische Bauteile | Bauteile | myhobby-CNC
-- datasheet http://shop.myhobby-cnc.de/media/pdf/nema17.pdf
- grbl_v0_8c_atmega328p_16mhz_9600

I wired the machine, but have not grounded the wires yet. See attached pictures.
The stepper motors are currently not attached to any belt.

I issued with UniversalGcodeSender the command
G91 G0 Y9999
as a test.


Reproduceably some seconds (about 20 sec) into this command the second Y-axis stepper motor loses steps (see attached video).
Another 10 seconds or so later the other also loses steps, it even seems the first-Y-axis-motor runs backwards for a very short amount of time.


I am not in a hurry to complete this machine, I rather want to understand things "from ground up".
Could anybody drop some lines about what might be happening here?
Why so late into the command?

I hope I gave enough input.

[cpr]

To improve my understanding of stepper drivers I looked at them with a Flir i5 thermal camera.

The temperature is not to be taken by face value, because I did not calibrate on the surfaces.

The pictures are showing:
- everything switched off
- USB cable connected
- a short jogging move
- a longer jogging move

[James Newton]

Nice testing though... I love the documentation. Let me know when you are ready to move up to something larger and we will work out a deal for a 4 amp driver kit in return for nice video and thermal documentation.

[cpr]

It is easy to produce _some_ pictures wih a thermal camera.
I need to work on accuracy though!

What is missing above is a proper calibration. Radiation from basically everywhere does end up in the picture plus each surface reflects differently. What I need to do is (roughly):
- put e.g. a sticker on a part,
- wait approx. half an hour for it to warm up to the temperature of its "carrier"
- measure with a contact probe the sticker's temperature
- and then calibrate the thermal camera to that value.

Thrn I can put stickers on other surfaces and read from the sticker's surface.

(When my brother bought this camera to evaluate his house he went for a training, too.)

On my picture there is a slightly hotter spot at one of the "terminal screws" in the upper left.
I took a mental note to check if the contact is not properly "closed".
So even with just relative, not absolute, temp readings I can already gain some information.

[cpr]

And it is interesting to see how quickly the temperature drops! Even these toy-drivers dissipate heat quicker than I thought!
I can't wait to test heatsinks and a fan!

[cpr]

And I already have an upgrade at hand, transaction code 621176418R107292U from end of march this year!

[James Newton]

And I already have an upgrade at hand, transaction code 621176418R107292U from end of march this year!

Ah! There you are! Several THB6064AH kits shipped. LOL... Well, when you get them built, post a thermal imaging test and I'll refund part of your purchase.

We also have an adapter cable that fits in place of the Pololu drivers and connects to the THB6064AH (or any of our drivers). In your case, its probably just as well to wire directly from our driver to the Arduino.