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.

 

Marlin ported to the TMC2209 board

I just got Marlin to boot and move the motors. Had to make some tweaks to the serial port configuration, because I have unique setup (X, Y and Z share one serial port) and the two extruders share another. I also use proper hardware serial ports, not the SoftwareSerial library. At the moment the code requires special patches to the STM32Duino core and the Trinamic library so it can properly support serial half-duplex communication.

On separate topic, I got a prototype of an LCD i/o board for the Nucleo-F407. I tested it with the REPRAP_DISCOUNT_SMART_CONTROLLER and was working flawlessly.

Here it is connected to my soldering machine:

The very first prototype had a bug, hence the little red wire. This adds support for the traditional EXT1 and EXT2 connectors that are popular with other boards. Graphics panels would require a little work, to convince marlin to use the second SPI hardware block.

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.

TMC2660 success at last

I was very frustrated with my failure to get the TMC2660 board variation running. I checked and double checked the connections, alas the steppers would not move at all.

I purchased one TMC2660-BOB kit from digikey and started experimenting with it, instead of my board. At first, I had the same failure – the stepper would not move at all. The software was a very simple Arduino sketch – what would be that wrong. Since the kit was designed by Trinamic, the hardware should be proper. Alas, no luck. I declared the TMC2660 chip cursed and moved to my soldering machine project.

Yesterday I decided to give the test jig one more try. After a few failed attempts. I spotted an error in the Arduino code – I was passing the incorrect CS pin in the driver setup. DUH!!! After a quick fix it was working.

Then I moved back to my original goal to test the thermal dissipation ability of my TMC2660 PrntrBoard design. I connected my board and started to torture test the motor driver. Unfortunately I was not able to run the driver past 1.5A RMS, which is a shame. I’ll try using a different motor with higher coli resistance. Anyhow here is an image from my thermal camera of the top of the ship:

The chip has no heat-sink and runs at 54C. This is not bad at all. much cooler than the TMC2130 version. The board seems to be dissipating quite a bit of the energy.

Here is a picture of the bottom of the board:

The bottom is at 45C in the center, which I think is quite good thermal conductivity of the board layers.

I feel good about the board thermal capabilities. If I add heat-sinks on the top and the bottom it should be able to run at 2A RMS and above with active cooling.

Soldering machine tests

I’ve been running the soldering machine for about 2 weeks. I added a very ugly, but effective fume extractor to the machine head.

It has 40mm fan and a square piece of carbon-activated filter to absorb the fumes. The design is not my best work and is held together with hot glue. However it does work.

Some early failures of the soldering were quite comical:

But some tweaks of the G-Code and it is mostly working now

At this stage it is completely manual programming. No computer vision at all. I’m recording all soldering sessions so they can be used for training ML models later.

My test board is fairly straight forward, so programming the G-Code is not hard. I use a simple C++ program to send the commands to the 3D printer controller. This allows me to add the necessary delay and in the future integrate some processing of the camera image.

I also managed to find an M12 camera lens with much less distortion, to the point that the image no longer needs corrections.

Computer vision mishaps

I was planning to add a Raspberry Pi camera on my soldering machine. I used a camera board from China which has the M12 lens mount. There is a variety of M12 lenses and one can play with the focus.

This is the camera board mounted on the soldering head

I finally got everything set up. I discovered this very nice camera streaming web interface package here is a picture of the web interface

The UI is simplistic, but allows control of the camera settings and while streaming is consumes only 3-5% CPU. Well done to the Raspberry Pi foundation and the RPi Cam Web Interface team.

Here is an image I captured with the camera

The focus looks good and the image resolution is very nice. However the vertical blue edge of the plastic mount is supposed to be straight. Not so much on the image. The 3.6mm M12 lens I used on the camera adds quite a bit of distortion around the edged. My other lenses are more on the telephoto side: 6mm, 8mm, 12mm and 16mm. I tired the 6mm lens and the distortion was better, but the field of view was too narrow and wan not capturing the soldering head. I ordered some more lenses which claim “low distortion”. We’ll see it they produce better result.

My initial goal was to capture a series of images and then “stitch” them together with OpenCV. Initial experiments failed miserably. First the lens distortion was confusing the stitching algorithm. I know that OpenCV has camera calibration option which can correct lens distortion, but I’ll try better lens first.

The other issue with the stitching was inconsistent lighting. I tried using my LED photo light, which helped initially. Still the lighting on some spots was low and some spots were too bright and getting lots of reflection from the PCB board surface.

I constructed this new camera head, which allowed me to mount a small ring of LEDs close to the camera.

I seemed like a good idea at the time, however it makes terrible reflections onto the PCB. So back to square one. I’ll make some combination of external photo light as well as some white LED strips. The goals is to have uniform light with minimal reflection and not to obstruct the movement of the machine.

Soldering machine progress

I managed to put together the chassis of the soldering machine. The bulk of it is made from parts for a Prusa MK3 3D printer. It provides a good start point so I can experiment further.

This is what is looked like in the beginning

I also put this mounting plate to hold the connectors that I need to solder for my test board. With this plate I can insert the connectors, place the board over and get it soldered quickly, then move to the next one.

Here is a video how the head would move along the Y axis

And another one along the X axis. This one needs to hop over the pins.

I used my PrntrBoard controller to drive the motors. This is a picture of the machine in it’s current variation. I added the Prusa LCD display, but have not connected it yet.