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.

Soldering automation (attempt 1)

I was researching how to make my 3D printer controller as scale. The usual option is to make a large purchase order from a manufacturer in Asia, but why not try a different way.

The issue with ordering from a PCB assembly house is that to make the process economical you have to place an order for 100-500 boards. For smaller batches it takes too much effort for the company to setup the machines. As you can guess ordering 500 boards is not exactly an affordable affair and mistakes are very costly.

I can make PCB production fairly efficiently. The most time consuming step is soldering all through-hole connectors on the board.

So why not try to automate that? As one of my favorite superheroes often says: “Maximum effort”.

I was inspired by this video:

I liked the idea of using a dispensing needle to guide the solder wire. However I wanted a bit more control over the angle of the solder iron and the solder wire.

This is a video of my first attempt to test the soldering tip mount. I used Hakko T12 tip with a soldering iron controlled from KSGER (aliexpress).

I’m planning to mount this contraption on a Prusa MK3 chassis. The plate on the bottom is designed to mount on the X axis carrier of the Prusa.

Extruder thermal control board

For a while now I had this idea – create a small board which controls the extruder heaters and fans.

Why – you ask? Well hear my theory. I have this old printer – the RigidBot. It has dual extruder – all direct drive. However I noticed that when it starts to work my temperature readings become very noisy.

Initially I was puzzled, why the noise. After some investigation I noticed that the noise is present only after the printer motors are on. If I switch the motors off (via G-code command) the temperature line in OctoPrint becomes smooth again. It turns out the motor current is creating EMF interference with the thermisor wire.

So I was thinking instead of routing all these wires back and forth, I can build a small board with a cheap CPU that controls the temperature. I can also outsource the control of the cooling fans and even add local display etc.

All the wires needed would be power and some way to communicate between the main board and the extruder daughter board. Audio cables are relatively cheap and well shielded – I can use one for I2C or Serial communication.

In a dual extruder setup one can save quite a bit of wires: two pairs of power wires for the heaters, two pairs for the thermistors, another two pairs for the extruder fans and one or two pairs for parts cooling fans. All these could be replaced with one pair for power and an audio cable for communication – the rest of the wires are all local to the board. Well one has to mount the board somewhere close to the hotends.

Long story short, the first version of the board was not a grand success. The power supply was very noisy and the temperature readings from the ADC were so unreliable, that it was throwing the PID into a weird loop.

Here is the second installment of the board. The power is now dual stage – a buck converter to 5V and then LDO to 3.3V for the micro controller. The LDO filters the noise from the buck converter.

The brain is STM32F030 micro controller. There are 3 fan connectors with tachometer inputs, so in theory the board can alarm if the fan stops working, just like the Prusa MK3. There are 2 thermistor inputs, 2 heater MOSFETS as well as 2 thermocouple controller inputs – for MAX31855 or MAX31865 or similar.

In the next version the voltage the fans would be select-able to whatever the input is (12V or 24V) or 5V. There is a bunch of unpopulated extension pins and an LCD connector for extra fanciness.

I was testing the PID in Arduino code and it works quite well this time.

Just for fun I decided to try my thermal camera to see if there are any hot spots. The picture is with the heater 1 working.

No surprises, the heater MOSFET is a bit warm. The hottest spot is on the buck converter – 37C. Don’t be alarmed by the bright colors 37C is barely warm to the touch.

I’m still trying to figure out what should I use as software platform. Arduino is simple, but somewhat limiting. The STM32 CumeMX is another option. There is MBed and FreeRTOS options if I want to try multi tasking. Oh decisions, decisions.

~V

The TMC2660 board was a bust

I dusted off my trusty pick and place and made one of the newly received TMC2660 driver boards.

Since it’s the first time I test this setup I populated only one of the driver chips – the X axis.

Alas it was all in vain. After fighting with it for several days, the motor would not spin properly. Either my stepper driver configuration so completely busted (although I double and triple checked) or the driver chip is fried. One of the phases works, but the other sends no current to the stepper motor.

Also I was trying to fit some automotive fuses on the board – you know for protection. Alas the fuse holders I ordered are very flimsy and don’t fit the fuses at all. Ordered a different set, but have to wait.

Bummer 🙁

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: