JGAurora A5 drivers without potentiometers

netzmark

Hi,

I'm changing A4988 drivers into 2208 just today.

And have found my original A4988 have no potentiometers, another genius simplification from the Aurora staff...

Being curious I have measured their Vref and found the every drivers are not identical, Z have different resistors divider and the voltages are:

X- 0.5209V

Y- 0.5209V

Z- 0.8422V

E- 0.5209V

Samuel Pinches

Fascinating! I had heard about these fixed vref A4988 drivers, but I did not know they were different between the different axis. Perhaps this should be applauded? Because poor stepper driver calibration is such a big scary problem for new beginners. Thanks for sharing!

netzmark

I didn't know too by now :-).

Definitely Z requires more current as it is two motors driving, so other divider for Z is reasonable.

I wanted only to point attention on it. If someone would need to take off every drivers for any reason - before an operation make some mark on Z driver...

These resistors have good tollerance (I think they are below 1%) and XYE drivers has identical Vref up to 4 position after dot. However resignation of pots is idiotic idea anyway. I wanted to increase the current of E and now must play with resistors, no big deal but not so easy as just normal pots adjustment (I exchange 4988 with 2208 only for XY).

Prokktor

Yes I took a picture before replacing them with 2130s...

Did not notice different resistors, but they had different soldering for me^^

netzmark

30C (20kohm) on XYE and 302 (3kohm) on Z.

One resistor difference.

Der_Muck

Oh maaan thats why on one of my 4988 controllers is a black line with edding on it. I changed it back on E and was wondering why my E stepper motor was getting hot -,-

Dont use over 500 mA for the E motor, the motor only gets quickly hot and you have no positive effect. Its the same with Y. 900 mA are fine for Z. Always check the temperature of the all motors after working on the controllers after 30min, 1h and so on (on the first print). 

netzmark

Yes this one obviously was tuned for Z which requires a bit more current than others.

I have little changed current for E (replacing resistor 20k into 15k and getting 0.6V instead of factory 0.52) to set it as recommended by forum.

"hot" is very relative. Steppers may work normally being very hot like 60deg. But generally you are right of course :-)

Der_Muck

Yes, normaly its ok between 60-90°C but the the extruder is melting or weaking the filament, thats a huge problem.
The motor is working good with 450mA even with that, the motor turns so strong that a stock filament cant stop it.
Recommended is relative, I dont know where those valves come from. The best is to turn the current little higher than the min. current is with what the motor is propper working. Thats enough and prevents overheating. 
My experimentations also came to the result that 450-500mA is enough, JGs settings are right there.

Prokktor

I have my Y and Z motors at 900ma with my TMC2130s, above that they do make very crazy noises^^ I will keep them at this maximum there because it gives me higher print speeds,

60 to 90 C is imho not fine... I built rc cars and helicopters for years and so I do have much experience with motors.
The hotter a motor gets the weaker the magnets get and the resistance of the copper windings increases. So it gets less efficent and heat output increases even more.

Since there is is temp gap between the inside and outside of the motor (depending on build quality usually between 5C and 15C) I would not want my magnets to be above 80C, that means around 70C on the outside of the motor.

The motor will fail immediately at around 120C magnet temp, but its life span will already shorten when above 80C.

Since the Y Motor is the only one getting hot when everything is set up correctly, i installed fan directly below it because JGAurora intelligently left a big hole in the chassis there. Now my Motor sits at arround 40C instead of 63C when printing at speed 80.

Der_Muck

Yeah I agree that the Y motor must be cooled. The opening is great there to be used.
I still think, the motors would be ok with around 80°C because they are 1.7mA motors and when you use those mA it will get that hot easy. But for that, active cooling is a must have. For the Y motor with 500-600mA a passive heat sink is good, active is better. For the E motor if you set it to 450 passive cooling is for savety.  I still think that the valves from daihai are much to high to use. 

Prokktor

If I go below 650 for Y or below 900 for Y I get layer shifts all the time... I cant go any lower.

Der_Muck

With the 2130?  Did you set them with SPI or with the poti? I set mine to 0.850mA with the poti and 500 with SPI.

Matt

(stumbled here searching for data to change the drivers) What? Excuse me, so the drivers coming installed by default in the stock a5 are already tuned/modified from facility?

Samuel Pinches

@Matt https://jgaurorawiki.com/a5/stepper-drivers

Answer: often poorly tuned.

Matt

Hi Sam. Well, still unclear to me how to tune them. Apparently the drivers I got from Aliexpress was plug & play: I installed in the sockets and the axis worked.