Maximum Motor Current - Duet 3 Mini 5+ TMC2209
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I did a quick search but didnt see much. I have the RatRig LDO-42STH48-2504AC motor rated at 2.5 Amp per phase. Using the Duet 3 Mini 5+ and the TMC2209, what is the maximum current i could safely run?
@dc42 indicated in the past that RRF specifies PEAK current in the M906 command, not RMS current. Just for clarity, the TMC2209 datasheet
specifies 2.8A peak current, 2.0A RMSseems to specify 1.4A when using an internal sense resistor.But all the Duet RatRig github pages i've come across all specify M906 X1400 Y1400 or i've seen one with M906 X1800 Y1800.
Couldn't i safely use M906 X2500 Y2500? To be clear with my current prints the motors are always room temperature, i never have seen them even slightly warm (extruder LGX of course is warm:)) Can i set my motor current to the rated specs?
M906 X2500 Y2500 Z2500 E800 I30 -
@rogerpodacter motors run at their maximum current get very hot - typically the rated current is quoted for a temperature rise of 60C or more. So although you could in theory run those motors at 2.5A, you almost certainly wouldn't want to.
Likewise the TMC2209 max current is quoted for a driver soldered to a large area of PCB all to itself for heat dissipation, which is not practical. So the Duet 3 Mini is designed with a hardware limit of about 2.3A peak, and the firmware currently has a lower limit of 2.0A. So 2000mA is the maximum you can set in M906. Try setting 2000mA if you like; but you will need to fan-cool the Duet, and beware if there are any plastic parts in thermal contact with the motors!
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
@dc42 well i did not expect this! i just increased all my motors to 2000 amp peak, and holy crap my printer is DEAD QUIET. since i've had this printer, during movement and homing, specifically the Z raising and lowering, has all had loud buzzing and vibrations during the movement. but now its so quiet i cant even believe it. i am going to run like this and see how hot it is. but wow is all i can say so far!
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@rogerpodacter we normally recommend running motors with the peak current set to between 60% and 80% of their rated current. So for your motors, that's 1500 to 2000mA.
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
@dc42 yeah so at 2000 mA the drivers overheated within about 10 minutes of running. I tried to find a middle ground where enough current reduces rough motors but still stay cool.
M906 X1800 Y1800 Z1600 seems to be on the borderline.
Driver 0.2 and 0.3 overheat and the others seem to be fine, i think because 0.2 and 0.3 are below the add on board which traps in some heat. 0.0:0.2 are my Z motors which are low usage, i would think X and Y would overheat first (these are 0.3 and 0.4).
The motors are still cold, its the drivers themselves that are hot. Using my heat gun, the drivers reach 90C, the MCU is 62C, and the internal reported temperature is around 62C.
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How are you cooling the board?
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@phaedrux well i have no cooling, just natural heat removal
.But something is weird, i moved drivers 0.1 and 0.2 to the expansion board 0.5 and 0.6, and the overheating seems to follow those cables. And they are Z motors, barely used. The X and Y never seem to overheat.
Is it possible i have poor wiring connections, causing high temperature? all 5 motors are cool to the touch, its only the drivers that are the problem.
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at 2000 mA the drivers overheated within about 10 minutes of running …
Driver 0.2 and 0.3 overheat and the others seem to be fine …
The motors are still cold, its the drivers themselves that are hot …
the drivers reach 90C …
well i have no cooling, just natural heat removal …
Seriously: do you want to fry your Duet? Before playing around with amps and wondering what’s going hot, read the board’s specs and provide active cooling - look here for details. Special note: cool the back of the board.
i moved drivers 0.1 and 0.2 to the expansion board 0.5 and 0.6, and the overheating seems to follow those cables. And they are Z motors, barely used.
Steppers not only need current when moving, but also to hold their position. So it’s irrelevant if they’re "barely used".
Using my heat gun …
As a proud owner of a heat gun, use it to keep your chips at or below 60°C: by this, you will keep your Duet alive for many years, even at 2 amps per driver.
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@infiniteloop i did read the cooling section when i received the equipment, but it indicates passive cooling is sufficient for most scenarios. I'm simply experimenting to understand my setup. i wont be running like this in normal conditions; that's why i'm determining the limits.
During this experiment I realized that the stock RatRig wiring are very small gauge, so i upgraded all my motor wiring to 22 gauge. I was hopeful, but it didnt help much with the heat on the drivers. it looks like anything above 1800 mA will overheat the drivers with passive cooling, so an active fan is needed above that.
One thing i dont understand, the Z drivers are the ones that overheat, but the X/Y hold up much better. perhaps because they work together which reduces their load to some degree? it doesnt quite make sense to me. maybe its just the area of the board i have my Z drivers are near the center, and XY are near the edge of the board, thus cooling it easier.
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@rogerpodacter
You can reduce the motor current when in idle with the 'I' parameter of M906 and:
There is another M-code(I just don't remember)which reduces the current during slow moves and standstill (like meshlevelling Z-motors)
That's the one you need//edit It's M917, but for some cases M913 is also useful
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@rogerpodacter as @o_lampe says, you can use M917 to reduce the motor current when a motor is not moving. The default is 70% of normal, but you might want to try e.g. 50% for your Z motors.
Fan cooling is definitely required when running the Duet 3 Mini above about 1500mA motor currents.
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I’m determining the limits
… or, as I would say: you risk your Duet. The hotter a chip, the faster it fails. Do you really want to determine the limits of the board?
I upgraded all my motor wiring to 22 gauge. I was hopeful, but it didnt help much with the heat on the drivers.
It can’t. That just helps you to pump more amps through the steppers and to dissipate less heat by the wires. The drivers still try to provide 2 amps if you tell them to do so in your config. As @dc42 told you several times in this thread: apply active cooling!
After you’ve done that, check the temperatures of your steppers. As long as these don’t exceed 60°C, you’re safe.
