Completed redesign of the TMC2660 branch

I spent a lot of time getting the PrntrBoard tmc2130 version to work. I’m at the point where I’m quite happy with it and don’t see major further changes. The tmc2660 branch did not get a lot of attention in the mean time.

So I spent a weekend completely re-designing the tmc2660 board. I ported all changes from the tmc2130 version. There is now a dedicated ground plane layer and routing it much easier.

I opted to put all drivers on one side of the board. Unfortunately limiting the size to 10x10cm (or 3.9×3.9 inches), I could not fit all drivers in one row.  Hopefully cooling would not be major PITA as it was on the tmc2130 version.

Here is a screenshot of the 3D rendering of the redesigned board:

Please excuse my mistake, the top row of power connectors is facing backwards. Fortunately these are symmetrical and I can simply solder them the other way.

Here is a view from the top:

I used very aggressive layout for the connectors and I ended with some spare space in the middle of the board. I was thinking to add two automotive type fuse holders for extra protection. I haven’t quite settled on what fuse holder to use. Here are two renderings with the footprints in KiCAD:

And view from the top:

All changes have been pushed to my GitHub design repository page. The version with the fuses is in the tmc2660-fuse branch.

Controller brain – replaced

While I was working on porting Smoothieware to run on my 3D printer controller, I was going back and forth between my trusted NUCLEO-64 F446 devkit and a new acquisition from china – the “Black VET6“. That was a very capable board with onboard SPI EEPROM, battery backup, micro SD card and USB connector – all this for less that $10 from aliexpress.

While the NUCLEO has the advantage of build-in ST-LINK debugger, I was missing the SD-CARD connector and the extra pins to work with.

The NUCLEO-64 uses only 64-pin micro-controller package and I was running out of available IO pins. For example on the Rev3 of my controller I has to use every last pin to be able to connect an LCD screen – and even then sharing the SPI bus between the screen and the TMC drivers was causing some issues.

Here comes a proposed solution for this issues: a NUCLEO-64 form factor board designed with a 100-pin MCU (STM32F407VE):

This was my very first try and I did not have all parts available yet, so you can see some unpopulated pads.

The board is the same size as NUCLEO-64, and has the same dual row connector on the back:

Here is a “fuzzy” picture of the two boards side by side:

The USB connector is micro-usb, which I think is more available. There is a micro-sd card slot and a plethora of expansion ports for future extensions like LCD panel, WiFi module or even more extruders.

I also added some SPI EEPROM so we can save settings etc. Last but not least there is a power supply module which provides 5V up to 3A from 12 to 24V input. The 5V and 3.3V from the CPU board are connected to the motor controller board so there is no need for an external 5V buck converter anymore.

The only slight disadvantage is that now I have to use external ST-LINK adapter to program the board and an external serial-to-usb adapter for debugging.

Here is a little video comparing the two boards side by side:

Tested LCD interface

I had one RAMPS discount full graphics controller laying around from my RigidBot. I did use it with the original controller and decided to test it with the PrntrBoard.

In Rev1 and Rev2 of the board I did not have enough pins on the LCD connector to be able to use all buttons on the panel. In the Rev3 I used every last pin of the tiny 64-pin package and I just got enough (or so I thought).

I learned the SPI used by the LCD panel is not very standard and had to fight with Marlin to make the TMC drivers and the LCD co-exist on the same SPI bus.

Finally I was able to use the panel:

One of the pins I used for the button input did not quite cooperate, so I have only one button + the rotary controller for the UI. Lucky for me both Marlin and Smoothieware were functioning with that configuration.

I had to disable the TMC diver monitoring, because the LCD controller was getting confused by the SPI communication with the TMC drivers. I think I can create a small breakout board with a few AND gates to alleviate this interference.

Here is a video of the panel working in Smoothieware:

 

Enclosure for the PRNTR board in OnShape

I finally got annoyed enough by the mess of cables and decided to finish an enclosure for the PRNTR board. I finished designing the bottom half.

This is what it looks like in the OnShape assembly:

View from another angle:

Closeup of the final assembly – the outer fan duct:

A look over the whole board:

And finally this is what it looks like, when powered up:

All 3D component designs are available in OhShape here.

More progress on the Smoothieware for STM32

After a few unsuccessful attempts, I got Smoothie to move my stepper motors on the PrntrBoard controller.

At first the smoothie had a bug in the SPI dirver and was unable to talk to the TMC2130 chips. Fixed that, then the steppers still would not move.

I can see the drivers were sending current, because my power supply would start the fans up, but zero steps. I spend the day trying to diff the configuration between Marlin and Smoothie, but nothing was wrong. Finally caught a bug in the Stepper timers and lo and behold movement.

I’ll make a video of my Rigidbot running Smoothie on STM32 next week.

Smoothieware on the PRNTRboard

Thanks to the huge work by Matt Baker, I now have Smoothieware V1 booting on the Prntrboard. Matt did an excellent job with the initial port of Smoothie to the STM32 series of CPUs. I did some tweaks and added a target for the NUCLEO-64 board I’m using. After a few weeks of work it does boot and I can verify the temperature controller works.

It does not have all features of the original Smoothie board (no SD-card and no Network) but I do have better drivers – TMC2130.

Here is a picture of me testing the hot end heater control:

The heater was set to a “safe” 55 degree Celsius. I would say the PWM control for the heater is much “smoother” on the Smoothieware.

My port of Smoothieware V1 is on github. My working branch is stm32f4. I also have stm32f4-tmc2130 with the TMC patches.

https://github.com/ghent360/Smoothieware-STM32F4

Here is a picture of the heater setup:

KiCAD 3D export + onshape

In my experiments with the rev1 version of the TMC2130 board I found that the motor drivers get quite warm with increased current. If I point a fan just right it would cool the driver enough, but if the air flow was not sufficient the drivers overheat quite easily.

I wanted to improve the cooling on the PrntrBoard motor drivers. The board layout is challenging with the NUCLEO board on the bottom and a bunch of connectors on the top. Achieving good airflow for the Trinamic drivers would not be simple unless I add many many fans.

I tried to design a custom airflow conduit that would direct the air over the drivers without taking too much extra space. To start I did an export of a 3D model of the board and all components from KiCAD – it proved to be an excellent feature. I exported a STEP file, which I then tried to import in onshape. It kind of worked, but the generated assembly was full of small parts which would move all over the place and there was no easy way to tell onshape that this was one solid block of parts (at least I didn’t find an easy way to do that). Not to worry I fired off a copy of Autodesk Fusion 360. Imported the file there and added models for the heatsinks I was using on the board. I also added the IDC connectors to the NUCLEO board (they were not in the KiCAD export). I tried to figure out the assembly feature in Fusion 360, but gave up and exported STEP file again and imported it back to onshape. This time it appeared as one giant part, so I proceeded with my favorite feature – “design part in place”. This lets you design a new part in the context of an assembly and you can use geometry from the assembly as reference.

This is what the current design looks like:

 

And here is how it actually fits on the board, when I created the parts on a 3D printer:

TMC2130 catches fire

A co-worker shared this story yesterday with me. He upgraded his printer to TMC2130 drivers and while he was testing how the new toys performed he got a message that one of the drivers overheated and then the driver exploded in a non trivial ball of fire.

I asked if I can have the driver for some pictures. The driver boards were clones from the usual Asian markets. He now has ordered some “legit” boards from DigiKey. Crossing fingers these would not burn his house down. Said unfortunate driver was on his Z axis and he was running it at 1.1 amps.

This is what it looks like, next to a working board from the same supplier:

(click on the image for better resolution)

As you can see the top of the board kind of exploded, with some of the copper traces melted away. I suspect when the driver overheated either a solder joint shorted or the board shorted internally and that caused the severe failure.

This is the bottom of the board, where the driver chip is mounted:

The damage looks less severe from the bottom. There are charred components, but no melted copper.

Here is the top part – where the copper melted under my microscope:

Another angle – close to the edge of the board:

This is the bottom side – you can see the chip is a bit burned and some capacitors have been barbecued.

Another view of the barbecue area:

The rest of the chip looks intact:

I removed the chip an this is a view of the PCB underneath:

All but 3 pads look in very good condition. Unfortunately the 3 pads have evaporated completely from the board as well as the chip itself:

I was wondering if the chip can be salvaged, but it does not appear to be within my abilities.

One more reason to keep a fire extinguisher handy and not let your 3D printer unattended.

PrntrBoard TMC2130 redesign is complete

When I was working on the new layout for the TMC2660 branch of the board, I used a dedicated ground plane and turned out this was awesome. It simplified lots of the routing as well as added good heat dissipation capabilities to the board.

I wanted to try and redo the layout of the TMC2130 branch with this technique. In addition I wanted to swap the location of the E1 motor driver and the 5V input connector, before the E1 driver was crammed in the corner and it was challenging to get good routing of the power pins. By swapping the position with the 5V power connector there is a bit more space.

The third thing I wanted to try was to reverse the position of the STM32 NUCLEO board – in the previous design it was sticking out in an unsightly manner.

So here it is new layout all complete. DRC checks pass.

In a slightly different perspective:

You can see the NUCLEO does not block the mounting hole on the lower left corner anymore (MK4).

Here is a look from the bottom:

The motor driver have large area on the bottom for heat dissipation. You can also see the large rectangle area on the bed heater control MOSFET on the top.

I also added a few extra power connectors – two for Vin and two to the 5V rail, to hook cooling fans for the case. You can see two of them on the low left corner in the last picture.

Note: while the last picture shows the STM32F411 CPU, the board actually required the STM32F446 version. The only 3D model I found for the NUCLEO STM32 dev kit was with the STM32F441 part, so that is why it is on the images.