simon.n2
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Made an external driver board for Rambo Mini - Feedback appreciated

Sun Mar 18, 2018 11:37 am

Hello everyone,

PCB design is absolutely new to me and also my electrical skills are limited. so I am looking for feedback on the first PCBs I did. My target is to add TMC2130s to my Rambo Mini and maybe modify the MK3 firmware to run on it (sans filament sensor, power panic etc).

Using a castellated daughter board to be soldered onto the Rambo Mini it will make use of the test points on the back. This way in Standalone Mode you will not have to adjust anything in Firmware. When using STEP/DIR you will need to connect MISO/MOSI/SCK and of course the respective CS.

Daughterboard PCB

Board scheme
Board PCB

I will make everything available as open source once it's done. Anything to be modified from your point of view? Should I for instance use separate caps for each driver?

Before you ask, yes, it is autorouted but I have adjusted some vias and routes. These were the autorouter settings. If there were any vias on power or driver output I modified the vias to have the hole diameter equal to the trace width and outer diameter twice that (i.e. on the driver output 0.03 inch hole diameter and 0.06 inch outer diameter).

Version 1 is running but I have quite some issues with whining when using SpreadCycle in idle. I also checked vmod's external driver board and it is the same. Can it be down to the stepper motor? I already tried upping the voltage to 24 VDC, but it did not change anything.

tobias.k3
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Re: Made an external driver board for Rambo Mini - Feedback appreciated

Sun Mar 18, 2018 2:41 pm

Awesome job! Do you also have some pictures of the setup?
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PRUSA MK2
- Noctua fan 40mm
- MK2/MK3 hybrid extruder

tobias.k3
Posts: 75
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Re: Made an external driver board for Rambo Mini - Feedback appreciated

Sun Mar 18, 2018 2:50 pm

By the way, I had a similar Idea. It is nice to work with genuine Prusa firmware. If you want to address the TMC2130 via SPI you can add a small arduino nano for the stepper configureation. which stepper do you have watterott or fysetc?
----------------------------------------------
PRUSA MK2
- Noctua fan 40mm
- MK2/MK3 hybrid extruder

tobias.k3
Posts: 75
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Location: Germany, Mainz
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Re: Made an external driver board for Rambo Mini - Feedback appreciated

Thu Mar 22, 2018 1:07 pm

By the way, in which mode are you running? spreadcycle or stealthchop? To which coil current did you adjust the stepper drivers? (I have little experience but as far as I understand, whining can be altered/avoid when changing setCurrent and voltage. Watterott recommends > 18 V)

Maybe you find some additional infos here: https://www.youtube.com/watch?v=UejSUgvbUgE

As far as I know it is better to use individual Capacitors for each driver to avoid odd interaction between the drivers. You might even add a smaller capacitor for each driver to counter high frequency voltage fluctuations.
----------------------------------------------
PRUSA MK2
- Noctua fan 40mm
- MK2/MK3 hybrid extruder

simon.n2
Posts: 18
Joined: Wed Apr 05, 2017 9:56 am
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Re: Made an external driver board for Rambo Mini - Feedback appreciated

Mon Mar 26, 2018 1:42 pm

Thanks for the replies :) In fact, Toms videos on the TMC2130 were the reason I started this little project :)

You can find pictures of the setup here, here and here and a video showing my "noise" issue here.

Y-axis is in StealthChop and X-axis in SpreadCycle. You can hear in the video that in StealthChop there is only little whine, but in SpreadCycle it is really bad. I already tried different PSUs as I assumed interference, but it does not seem to be the reason. I also used a boost converter to increase the voltage to 24 VDC without any improvement.

I use original Watterott drivers, bought directly from the source, this is why I'm surprised about this. I've only heard about this issue from cheap chinese knockoffs.

Using an Arduino in between is a good idea and has been used by Marco Reps. I might give this a try with an Attiny85. This way it should be possible to use the sensorless homing without any changes to the firmware.

tobias.k3
Posts: 75
Joined: Fri Mar 24, 2017 1:34 pm
Location: Germany, Mainz
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Re: Made an external driver board for Rambo Mini - Feedback appreciated

Tue Mar 27, 2018 8:36 pm

I am experimenting with the TMC2130 Fysetc V1.0 in standalone mode (The Chinese Knockoff) and get the same whining at 12V. :-(

Couldn't solve it :-( I will have a second look. but you already tried all ideas I have
----------------------------------------------
PRUSA MK2
- Noctua fan 40mm
- MK2/MK3 hybrid extruder

simon.n2
Posts: 18
Joined: Wed Apr 05, 2017 9:56 am
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Re: Made an external driver board for Rambo Mini - Feedback appreciated

Tue Mar 27, 2018 8:52 pm

tobias.k3 wrote:
Tue Mar 27, 2018 8:36 pm
I am experimenting with the TMC2130 Fysetc V1.0 in standalone mode (The Chinese Knockoff) and get the same whining at 12V. :-(

Couldn't solve it :-( I will have a second look. but you already tried all ideas I have
Damn. I could at least try it out with an Einsy and therefore confirmed it's neither the PSU nor the stepper itself.

tobias.k3
Posts: 75
Joined: Fri Mar 24, 2017 1:34 pm
Location: Germany, Mainz
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Re: Made an external driver board for Rambo Mini - Feedback appreciated

Fri May 18, 2018 2:25 pm

Any news on this project?
----------------------------------------------
PRUSA MK2
- Noctua fan 40mm
- MK2/MK3 hybrid extruder

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