TMC2209 design thermal tests

I did some simple thermal tests on the TMC2209 board. In theory these driver chips can supply up to 2A RMS current to the motors. Silent StepSticks with the same drivers are rated around 1.2 to 1.4A depending on the manufacturer.

The test setup

I used all passive cooling. Ambient temperature was 25C. I used a small 9x9x12mm heatsink on top of the driver chip. These are commonly used on the TMC2209 StepStick boards from China (FYSETC or BIGTREETECH). These are not great, but that is what I could fit in the space. I’ll try to move some of the capacitors to make space for a larger heatsink.

On the bottom I used a 20x14x6 heatsink. Not ideal, but that is what I had laying around. There is enough space for a much larger one (25x25x8 for example).

I used a Seek thermal camera “mounted” on a small microscope stand and connected to my old Nexus 5X phone.

The results

First I tested it at 1A RMS current. I use several very slow speed motion commands (G1 Y250 F50 followed by G1 Y0). I found that slow speed motion is much more challenging to the driver heat  wise.

After about 20 minutes it board heated to about 47C on the top:

The heatsink was barely warm to the touch. In my experiments the top of the drivers always heats up more than the bottom, probably because of the relatively large thermal mass of the PCB itself.

Next I ran the board at 1.4A RMS. This was more challenging test for the heat dissipation. It took a while for the temperature to stop rising. It stabilized at around 64C on the top:

And around 55C on the bottom:

In the picture the heatsink looks “cool” because the camera can not compensate for the different emissivity of the bare aluminum.

Both top and bottom heatsinks were considerably hot to the touch. Not “burn your fingers” hot, but “I cant keep my fingers longer that 5 seconds” type of hot.

In both cases I did not get any over-temperature warnings from Marlin. I would say 1.4A is the limit on convection heat dissipation of this board in this configuration.

The Seek camera has around +/ – 5C accuracy.

I did one last test at 1.8A RMS. This was on the extreme side of the capabilities of the board. The temperature of the driver kept climbing slowly. Once it reached around 75C on the top I got an overheat alarm in Marlin, so I turned the power off.

I’m confident with some active cooling the driver would be able to run at this setting, because it took quite some time to get to the alarm.

 

Some early experiments with the TMC2209 board

Good news first: I managed to get one motor moving with a simple Arduino sketch.

I’m starting to hate QFN packages with a passion. I spent a whole afternoon trying to re-work two pesky drivers. The chips would not communicate via the UART port, no matter what I tried. Finally traced the issue to a bad solder joint on the QFN package and boy these are hard to spot. Simply re-heating the drivers and re-positioning was not enough, I had to remove the chip, add more solder paste, melt it, then re-insert the chip, wipe the excess solder with a soldering iron and finally re-flow the chip one more time. Complete and total PITA.

To top it off this destroys any near by plastic connectors, so now I have the drivers in-place but have to re-solder the connectors back. This would be an endeavor for the next week.

Now all 5 steppers are communicating with the MCU reliably. I had to add support for half-duplex mode to the stm32duino core. The proposed changes are still pending, but I verified that the TMCStepper library is able to communicate with the drivers.

First prototype of the TMC2209 design

This took me whole day. Working with QFN drivers is plain PITA. It does look good though. I just hope it works.

I finally figured out how to wash most of the flux from the board. It is still not perfect, but looks really good.

I have another revision with 3 fuses. I figured that one fuse for both motors and extruder heaters may be too taxing. In my latest design I have one 15A fuse for the heated bed; one 10A fuse for the extruder heaters and one more 10A fuse for the rest of the electronics.

Added some useful features to my Marlin fork

I maintain a separate fork of Marlin with some tweak that enabled features specifically for the PRNTRBoard. The code is located in github.com .

Last weekend I spent some time adding some minor, but useful updates. First I finally got to enable support for the sd-card reader on the Nucleo-F407 board. It took a while because typically Marlin uses SPI to communicate with the sd-card. However the STM32 has much better hardware module (SDIO) which allows excellent transfer speed.

So it took some time to research what is the simplest way to add SDIO support to the Marlin firmware. There was already support for the STM32F1 series CPU, but it was written using a deprecated library (libmaple). Long story short it is working fine now. The code is in the f407 branch.

The second feature I wanted to enable is the ability to store the printer settings. Usually this is accomplished using I2C or SPI EEPROM chip. Alas I did not add one to the Nucleo-F407 board. I added an SPI flash instead.

The difference is small but significant. EEPROM chips are small, but can sustain millions of data re-writes. In contrast SPI flash chips are relatively large (the one I use is 2MB), but can only support around 100k re-write cycles.

There were two possible approaches, one use the sd-card as storage. This was already supported in the Marlin firmware, so I simply ported to code. The disadvantage is that it depends on the presence of an sd-card in the slot.

The second approach is called wear leveling – using the fact that I have relatively large storage and spread the writing operations across many locations in the chip. This way if I spread the write operation evenly across 100 separate locations I’ll achieve 10 million re-write cycles.

The error leveling code is relatively simple. For the curious you can find the changes here.

Next I finally decider to make a converter board for RAMPS style LCD controller modules. The files are checked in the main PRNTRBoard github repository. I placed and order for a few prototypes – they should be arriving in a week or so.

PRNTRboard update

The TMC2130 version of the PRNTRboard is working very well. I’ve been using it for over 6 months on my soldering robot project. It is very stable and reliable.

I didn’t have time polishing the Marlin firm ware for it. I wanted to make the SD-card work on the F407 Nucleo-64 replacement board. Alas every time I look at the Marlin code, I loose all hope and start doing something else.

A few months ago I started working again on the TMC2660 version. This was the first variant I routed successfully, but I ran into trouble with controlling the drivers over SPI and switched my effort to the TMC2130 version. Long story short, when the TMC2130 was in a good shape I started looking back at the TMC2660 version. It is on rev 5 now and I’m really happy with the layout. In my opinion it looks much better than the TMC2130.

I managed to produce a working Marlin firmware for the TMC2660 board and tested a few motors. So far it works like a charm.

My only gripe is that while the mate black finish looks awesome, it is absolute PITA to clean the solder residue from it. I washed this board 3 times and you can still see some spots on it.

As a kick all thru-hole pins on the Nucleo-F407 board underneath are soldered using my soldering robot. On the TMC2660 I soldered the two headers with the robot.

Last but not least I started working on a version with TMC2209 drivers – these are quite capable and low cost compared to other Trinamic offerings.

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: