DIY 3D printer part 8 - making a UNIPOLAR stepper motor driver for my 28BYJ-48 based extruder!

Here's the test code I used:
Bidirectional speed control potentiometer:

Affiliate links* to the ICs and some parts I got for this printer:

Keep in mind I got a few of these items during sale, so the total might well be above $50 now (especially with inflation)

* if you decide to purchase something through an affiliate link I may receive a small commission
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[ChronicMechatronic]

Should I make Chronic UniStep open source?
Also apologies for the slightly sub-par audio, the cable on my DIY lavalier microphone broke and I didn't have time to fix it, so I had to use the modified $2 AliExpress mic I still had laying around...

[Kato]

Your videos are a pure joy to an engineer. The act of inventing everything in your designs really shows how many workhours it is needed to make A Thing, and how masterful are you at pulling those workhours

[LuisMzles]

You need to dry your filament. Great video by the way. Thank you!

[joetkeshub]

About the brittle PLA: Most of the time moisture is the main PLA filaments enemy. By experience I know that like foods, PLA filaments can't be stored a long time. I guess bad molecule chains are the culprit. I run across such annoying surprise with some 3yo (cheap Geeetech) PLA filaments. I've tried to "dry" them in my tiny oven but that didn't fix it. I had to dump a quarter of a thread to get its printable part. Don't buy bundles, some batches have the same issue.

[joetkeshub]

Enthusiasm, humor and self deprecation PLUS skills, make your posts unique and irresistible Ben! One can feel the huge amount of work to get that perfect video editing (a great tempo) and of course to achieve unusual challenges we can't see elsewhere. Thank you Ben!
(FR) ça passe très vite 22 minutes avec toi. Tout y est: le rythme, l'humour caustique, le zoom sur les détails (presque une obsession nipponne) et l'explication de tes choix. à propos, monter les CMS comme tu le fais, défie les tremblements de mains de certains soudeurs.😄 En fait, ta pince est d'une indispensabilité bien pensée. Ton driver de même.

[roadshowautosports]

3:06
Brilliant idea!!! I’ve always struggled to make acceptable round parts on the grinder but there you come to save me!!!

[lazer]

I love custom motor controllers because they allow you to make it just right for you needs

[rizalardiansyah]

This really do deserve more attentions!

[jonathanrainwater]

if you want your PLA not to be brittle, I would suggest putting it in an air-tight container along with some silica gel packets (the white bag that is inside your filament box. hope this helps!

[KING-wjui]

As the next project i recommend you to make a heating plate for smd soldering, i've already made my own and i suggest you to make the same for save a lot of time.
Anyway nice video as always

[AaAa-hkng]

Thanks for making this kind of video, it's really helpful

[COSMOSIS]

No PLA isn't usually that brittle. In fact, it usually has a high elastic limit. You could try drying it out, but I think it's just a crappy brand. I have $19 PLA rolls that I've stored for over a year in the open and they are still almost perfect.

[lunarz]

Your PLA has absorbed a lot of moisture and has became old, if you can dry it try that, but I would get some new filament.

[samuelbentz]

The motor skipping steps when the direction changes might be a problem for the extruder too, not just the x and y axis. This is becuase you won't be able to do retractions.

[HunterNX_s]

If you have a PIC programmer (PICKit), you could use the PIC12C508A for unipolar stepper driver logic. I'm a fan of using logic gates for simple things, but one of the advantages of using these microcontrollers is that they reduce the complexity of pins (reduce time to solder), in addition to being cheap. The PIC12C508A has 6 GPIO's, 2 can be used for dir and step and the rest for the coils.

[davideliasfloresescalante]

try with different delays between those changes of direction.. Best regards

[woodyouloveit-fesw]

Sir can you create String Art machine(also called thread art) using this setup...seems easy for you...

[ivanivanov]

The PLA probably was wet at some point

[Enigma]

To reverse a stepper without losing steps, the step sequence must run in reverse (e.g. when reversing, next step is now previous step). I suspect that since you are using two 4017s, they are not perfectly synchronized in that way (in other words a discontinuity when reversing direction). If you want to do this precisely in hardware, then I think a more elaborate state machine design is needed or maybe you could use a binary up/down counter with the outputs decoded to the desired step sequence. Of course a microcontroller could manage this perfectly in software, but I understand you want it to emulate the interface to the bipolar driver.

[iCODeRUS]

you need to dry filament and it would stop being so fragile. specially one that was sitting and waiting ages to be printed :D