popping is probably due to moisture, usually it is released in the pre-heat phase of the reflow

I would love to see how that looks with magnetic film on top!

"In theory should work", I say this all the time when not is working properly haha

İ think, you have to increase the count of coils if you want more precise steper motor. Not 4 coils but 8 or more)

I would be interested in oscilloscope traces of the phase current. Due to the low phase inductance (air core...) I imagine the current ripple to be huge, making microstepping very hard to impossible

Hey man, I like your videos. Love how you show your R&D steps and how you go about trying to solve issues you run in to. Keep it up!

_Hi Carl! When spreading solder paste, instead of using flimsy business cards, pick up a few blank RFID cards from Ebay._ 👍

We use 7 pole (14 total lobes) steppers with 1/256 micro stepping as our tracking motor for one of our telescopes. Pole geometry is important as all poles need to be wired the same way, so as the have the same entry and exit point on all phases to have consistent magnetic fields.

Very nice! I believe the big issue is the dead zone between the coils. You may be able to fix it by stacking two layes of (shifted by 45 degres) coils on top of each other - either by multi-layer pcbs or by putting two PCBs on top of each other. In such a way the magnet will always be under the influence of some coil - and you could have twice as many steps per rotation.

I am also not 100% familiar with steppers, but things I would look at first: *) Geometry of the magnetic fields is important, Normal steppers have shaped soft iron cores, the air gap between coil/core is very important due to magnetic reluctance. Making it more reliable was a good first step, but I can imagine that the fields you generate are a bit too "disjoint". Increasing the number of poles, like suggested in another comment, might make it a bit better. The strongest force are at the points with least gap. This also means that you don't get a lot of force between steps. Maybe disassemble a bipolar stepper motor to look how you could apply similar principles :) The shape of your magnets is very likely relevant too. *) I am pretty sure you did that, but the drivers you use have a lot of features, that improve current usage and noise. These are designed using real stepper motors in mind and the algorithms they use might get "confused". I think they might use back-emf to measure some parameters. So disable all those features during debugging and maybe use 1/4 and 1/8th microsteps. Edit: Thanks for these very cool projects and sharing them online! There's so much we can learn from it!

Beginners will also see the horrendous price tag Altium has and that’s probably also the reason why a lot of hobby and later job people will not use it i guess.

the answer to your problem is shown at :15 seconds. you need more "teeth", four poles, 2 phase is not enough. have you tried stepping a 3 phase brushless?

That was incredible!! I would love to see more videos on this!!!

brilliant work! You are such an inspiration. Thank you for making such videos.

Seems like you had a great learning experience. The work u did seemed quite challenging to me. Good luck with the next iteration!

First video of yours I've watched, and I really enjoyed it! + Subscribed!

Your videos are so interesting and when so ever I see them in my feed I can't stop myself to watch it again and again. Watching this video 6th or 7th time.🤩😍

I think it because is a small amount of moisture and when you heat it slow it has time to evaporate but when you rapid heat it is like exploded also it happens to some chips if you don't put on an oven at 100degrees for at least 2 hrs, it is called popcorn effect

The reason you are getting the jumping effect is caused by a high transient response (overshoot) per step angle. The way modern stepper motors mitigate this is by increasing the number of phases and poles to decrease the step angle for more precise steps. That's why in the hybrid motors you were talking about in the beginning, by using teeth those types of stepper motors are able to decrease their step size to fractions of an angle compared to the permanent magnet one you built. Lowering the speed and adding a type of dampener will also help prevent the high overshoot! Using an H-bridge motor driver is also usually the best option for stepper motors.

You can just septate the flex PCB from the stepper board and use fingers to attach solder the coil flex PCB to main pcb (similar to LCD Cables). You can also try 1.6mm @2oz copper, and 0.4mm @ 1oz and play around with that. Your issue with components is you did not let the pcb soak and the flux in the paste popped your components. This is an awesome project non the less!! Super awesome work :)

can you "reflow" some butter and kernels to a Aluminuim sheet to see if the popping still occurs?

Awesome work man

What solder paste are you using. The stuff I bought isn't any good, and I'm looking to replace it.

I know this is 2 years later, but did you ever get the communcation with the single wire uart working? I ran into a very similar issue and after much headache, I discovered that trinamic used a different wiring convention for tx/rx then I was used to. Essentially, instead of commecting the uC rx to the trinamic tx, (and tx to rx), you have to connect the uC tx to the trinamic tx (and rx to rx).

Hey, looks great so far :D Have you thought about putting some iron core into your four pcb coils? Should be very beneficial for the inductance and fore of the coils :)

Amazing this video 👍 l hope created more PCB design project with you...

keep at it my friend!!

someone else mentioned this already, but they jumped likely because of moisture and yes, the rapid temperature change. many parts mention in their datasheet that you need to bake them before soldering

Amazing job ! can you share with me the name of that software?

_Hi Carl, the rotor is responding erratically because the magnetic flux distribution contains regions of varying density._ _To be more precise, the flux is strongest at the axis of each coil. And it is weakest where two adjacent coils abut together._ _Try laminating two flexible coil circuits with a 45° offset. Then write new code that energizes the coils in 45° increments, rather than 90°._

Truly innovative and knowledgeable video🤩😍

How those pcb traces are laid in altium, is there is any function to use

i need to make a mini magnet piston to move one axis about 1cm. Do you know any similar project?

With lots and lots of experience with PCB making.. I can say that Stencils and Solder paste is sometimes worth more trouble than it is worth. I generally hand solder everything and use a hot air reflow for SM components with pins under the IC. I think the poping could have been caused due to moisture in your components as well as the ramp up in temp.

The components jumping has happened to me before! It's due to moisture in the solder paste... after it happened to me, I checked the expiration date on the paste, it expired three years ago, lol. The issue is not from the hot plate, I also use a hot plate and it works fine, mind you I use leaded solder and have the temperature set to 200 C. Use fresh solder paste! I highly recommend the thermally stable solder paste from Chipquik, it does not require refrigeration for storage (it can be stored at room temperature): TS391AX

I love this application

Have you (would you) consider using nitinol memory wire in a small robot project?

Creo que tus inventos tendrían una gran aplicación en medicina Biomecánica, increíble lo que haces, eres un loco con buenas ideas!!!

Just found this channel. Suprr awesome. Would be interested to find out how the pcb coils do for power generation. Definitely strong use case for the form factor

Love this project. Im happy you shared this even though it wasnt as successful as you probably wouldve liked.

In 3D printing there have been problems with unofficial TMC driver modules not working with UART because some pins needed to be set to switch it from SPI to UART. I remember having to get my soldering iron to short some pins on my boards but I can't remember what they were. Maybe it's a similar problem?

Very cool! I think the other direction you could go with this is field oriented control, which may be more natural to implement with the pcbmotor designs

Very interesting project! I hope to see more of it. Maybe more phases would help with your skipping problem? Either that or more turns per phase.

Is it somehow possible to use this as a rotational sensor? Would be super-useful.

How do the coils perform as alternators?

Your one of my new favorite youtubers

Which solder paste do you use?

We use normal 30$ otg oven and control its temperature using provided knob. Also, while soldering we need to heat from both sides of the pcb, which is only possible in otg oven. It works great and we have probably soldered more than 100 pcbs within 1 year.

Oh man, this looks like an amazing application for watch complications.

Would using an odd number of poles on the stator and an even number on the rotor help? (Or vice-versa?)

I would love to if you could get a cheap absolute encoder onboard and try closed loop control.

I was thinking of adding intentional magnetic "cogging". Basically it's a bunch of iron "spokes". The spokes concentrate the magnetic field in specific areas and "lock" the magnetic rotor.

The reason stepper motor stators and rotors have ' ribbing " is to force the magnetic force lines between them. If you have any magnetic/conductive fillaments, try making what would look like a 3mm set of line li,e a clock face for the stator side and similar for the rotor. You missed the why of the stepper motor manufacturing and an accident on a stepper had me tear it open several times to find the lack of fins on my rotor meant it skipped. Good work so far, keep going!

Great video Carl. Wondering if you would see resolution improvement using 4 magnetics. Subscribed!

I think because the coils have very wide wire bundle it makes the area between two adjacent coils have no magnetic field and so the rotor become "loose" in those areas and is not stepping anymore until it's caught above the next coil

I wonder if the reason for the jerky motion is because the field from the coils is not uniform? Perhaps the phase difference between the coils needs to vary over a full cycle?

@Carl Bugeja you have to add more coils to the flexible pcb if you want to have precise and more steps

How about stacking two flex PCB's but 45° apart so their coil overlap?

Please, give link to the video about micro stepper motor you mentioned (“from 2016”) on 0:58

Amazing video as always!!! I feel that the skipping issue may have occured due to the number of coils on the PCB. This may change with the addition of coils. Great video as always!!

Great work. I think it was skipping because the magnetic flux wasnt strong enough to get into a steady motion. Higher coil winding or increased current could generate more flux. Try increasing current, it might work more smoothly.

At the top of the coils the H field lines will be going horizontal. Have you tried turning the magnets on the rotor to be horizontal vs the up/down ? Ie N/S in the fixed magnets will be coplanar to the PCB.

Can you also comment about the torque characteristics of the pcb stepper motor.

What's the scope output?

Have you tried pulling the mode pin (pin 9) of the TMC chip to ground? That should change it to UART mode

If you look at the timing of the skipped steps it's consistently at the center of coils. You need an offset, either an extra magnet or extra coils.

cool project! Try cooling it on a peltier plate so you can pump more current through the coils without overheating. also try visualizing the magnetic field with magnetic field paper while the motor is running. i bet that would look super cool to see the magnetic field.

There needs to be more poles on both rotor and stator in such way that when coil is activated there is always rotor magnet "close" ... so basically there needs to be magnet between poles in every position. That way the motor steps forward all the time. Also suggestion is to add hall-sensor so you know what position the rotor is so you can control more accurately the motor.

I think if add more coils, you can manage better the magnetic fields. I love your projects btw

Maybe your PCB motors are more suited for low-load / high-speed applications like an ultra thin fan that cools down a PCB. Keep it up!

Awesome. Keep it up

The problem is the wide variation in magnetic field across the poles. Either make the poles smaller or the magnets larger so that the varying magnetic flux is evenly distributed when interacting with the permanent magnet. You can use the magnetic field simulator software to get the flux map of your design. Increasing number of poles will certainly improve things. Commercial stepper motors have much larger number of pole pairs and equally large number of alternating permanent magnets in the rotor.

I wonder if the orientation of the coils cause the problem. As I see it the magnetic field goes up / down perpendicular to the pcb. Wouldn't it be better to have a long rectangular pcb with several coils side by side and roll it up to a loop. So the magnetic field would point inwards to the axle? But I'm just guessing

moisture in the components is why they 'popcorned'. usually smd parts have a moisture ingress rating and if the parts are exposed to atmosphere beyond a set period of days (or hours even) they need to be tossed in an oven for a bit.

Congrats on moving to New lab.

Hii, Could you tell me Which software you use to code these Circuits?

The problem of popping the chips out of the PCB is because of the moisture forming in between the legs of the chips and the PCB. Some distributors that deliver this kind of integrated chips put the chips in antistatic bags and after that they put also bags with silica gel to prevent moisture to build up inside the package, my distributor put also a sensitive paper in the package in order to see if the chips are contaminated with moisture. The theory behind is very simple, because of the temperature that rises quickly the small particles of moisture expands very quick and pressure builds up resulting a small thermal explosion that pop’s your bits of solder away an the small components also. I hope I was useful enough.

I think this would be a great opportunity to get some magnetic viewing film to try and observe the actual magnetic fields produced. Also about the flexible PCB dilemma. Would it be possible to have some standard ones made with one coil and the connectors and so on and then get one of the "coil pads" from one of these prototypes and glue it on top of the coil on the hard pcb? this way you could get the stability of a hard PCB but also the stronger magnetic field from the flexible ones? and use the one coil on the hard PCB to augment that further?

Nice work !, i think u should use a regular pcb for better performance

Carl, check the datasheet for the driver and you will probably see that the microstepping amperage change follows (mimics) a sinusoidal wave. This helps fast turning motors run smoothly. HOWEVER ... if you are doing single steps, you will get almost no step change near the peaks and valleys because the amperage isn't changing much, and then big changes in between when it is. So, it always looks like it is skipping, even when it is not. The only way I can get equal steps is by using a dual h-bridge and full or half stepping manually (with my own code). Hope this helps. It really frustrated me until I realized what was happening. Those drivers just aren't really designed for single steps. Or at least not equal single steps.

Dealing with tiny tiny steppers now (20 step/rev 8mmx8mm) and trying to microstep. Scope your voltage lines to the motor. What you might see if it's the same problem is that the current saturates really easily and instead of a sinewave looking waveform you end up with a few steps and then saturation. I've been fighting to get this down, but most drivers have potentiometers to set current and setting to things like 0.03v is hard with these parts to set things like 70ma current which is also out of spec for the the drivers. I've confirmed this behaviour at microstepping on 8825, a4988, stspin220 and trinamic 2209. Doesn't matter which, if current setting is too high it'll saturate quickly, so you need it very very very low and then limiting microstepping.

While using bigger stepps, it looked like the problem comes from I think has the name Oversteering. that means when it starts moving it accelerates to a speed, where the magnetic field isnt strong enough to hold it in the next position and the inertia brings it to the position after his designation. to test if it is the problem increase the amps or make the spinner as light aus you can.

This is definitively the best "sponsor integration" I ever saw o/

This is a wonderful project, I suggest you another amendment to make the rotor steps more accurate, which is to design small copper coils on the perimeter of the circle so that each coil acts as a magnet that attracts the rotor I apologize for the linguistic mistakes.

I guess you want to store your solder paste in a box with some silica thingies to keep the moisture down, just like you would with filament Or ramp the temperature to release the moisture, but I think avoiding humidity in the first place sounds like a good idea too

Please check if phase coils should overlap for proper operation of motor (say one phase coils meet at the middle of second phase coil). Best Regards

where can i get one of these tiny stepper motors?

What's that LED green pcb star on your wall?

your reason for using a flex pcb is to get the 2 layers of coils closer together, this would be more expensive, but maybe you could try using a multi layer pcb, if sticking with 2 layers of coils, get a 4 layer pcb and the coil is on layer 1 and 2 (or design it with 4 layers of coils) (idk if this would work, still very new to this stuff, never designed a multilayer pcb, so idk what other considerations you would need)

In commercial environments, solder paste is flowed using IR being directed towards the board as opposed to conducting the heat through the board. This method would reduce the amount of heat load you'd be introducing into the substrate. It seems like direct heat from a heat gun, IR panel, or an oven situation, might be a better solution. Just my 2 cents

I've had issues trying to talk to TMC drivers too (TMC2209). I might be wrong, but I think you have to start with a disable pdn_uart command to shut down the other mode of the UART pins. You might also want to make sure that all your message bytes are individually reversed for the crc, so when adreasing register 1, you actually feed 0b10000000 into the CRC.

3:05 Jummy, fresh baked chips on slice of copper haha. Like you said at the end of your video, you need more coils. I have never seen a stepper motor with only 4 coils. Nice detailed video, greetz.

Did you try inverting the UART output? Some datasheets have a habit of showing the data as active-high (logically), but the signal is really active-low. Worth a shot. Is it also possible that because of the design of the flex PCB, the Trinamic driver isn't seen the same amount of back-EMF from the rotor, so it can't get proper feedback from it? On normal steppers, the rotor is quite solidly "captured" in the magnetic field.

Is this a full flex pcb or a rigid-flex pcb?

The rings inside motor coils are looking like metallization. If it so, it can act as a short circuit turn in the coil and would strongly affect driver in micro stepping mode.

What would be the torque output

Also neodymium magnets has metallic conductive coating. Alternating magnetic field is inducing eddy currents in this coating which reduces motor efficiency. Try using magnets without metallic coating. Coating can be acid etched from available magnets.

so interesting!

When you put that pcb on the hot plate I thought about Italian pizza :-)

I like the concept, I've never seen a pcb motor before. You should check the magnetic fields generated with a magnetic viewing film. I think you may be getting some back EMF and eddy currents.