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Engineering Roundtable - The SpoolMaster 9000 with Paul

Check out today's episode of "Engineering Roundtable."

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Over the last several years, E-textiles as a niche of DIY electronics has really expanded. As such, we offer a number of seweable electronics kits and products, many of which include a spool of conductive thread. Our kitters discovered that manually spooling the thread from large spools onto the smaller spools was a bit of a pain. Fortunately, we have Paul, SparkFun Mech-E, to create awesome solutions to all our problems.



Paul used a couple stepper motors, some 3D printed brackets, some hall effect sensors and some other bits and pieces to create an automated conductive thread spooling machine - the SpoolMaster 9000!

As always, feel free to leave any questions or comments below - we'll be back again soon with more "Engineering Roundtable."

Comments 28 comments

  • I don't want to sound like I'm ragging on you, because that's a neat rig.  However a big part of my job is programming winders for sheet steel up to 3/4" thick, so here's a few concepts you might be interested in - "Dancers" and "Torque Control."  A dancer is a feedback mechanism that monitors the tension of your web.  I typically use inclinometers, but you can use encoders, reactors, differential transformers, or just potentiometers.  Let the dancer "ride" on the web, and then use it's feedback as an input to a PID loop controlling the torque reference of your winder or unwinder.
    Now, to use torque control you can't use hobby-servos which all run in position control mode via PWM.  You can use "proper" servomotors, which are expensive, or you can use DC motors with a PWM driven motor driver board.  Use the current feedback as the setpoint variable in your PID, and you're golden.
    And never drive two steppers on the same winder, that's rule one.
  • Oh, BTW, I like your idea of using the servo to distribute the thread, I'd been working on something similar and wasn't sure what I was going to do about that part, now I think I'll pinch your idea if that's OK :)

  • You forgot the most important part, the knob that goes up to 11 !

  • Impressive project!
    Since the thread movement against the flat spindle somewhat replicates the motion of a sewing needle on a sewing machine, using a pre-tensioner mechanism similar to what's used on sewing machines might reduce jamming and make the operation smoother/faster. The pre-tensioner on a sewing machine is the arm just above the needle that bobs up and down with the thread looped through the end. Also, a grayscale optical encoder on one of the steppers could quickly establish jam detection if it deviates from the expected bit pattern, and provide a way to alert that it needs "assistance".

  • I gotta tell you, Paul... That's a really clean layout for the tool. The wiring is nice and simply, redundant parts are there when they make sense for simplicity and reliability. I wish I could have had a cool job like that when I was15!

  • I love the way you used 2 steppers. Completely simplifies the hardware at the cost of a trivial duplication of motor drivers. I find giving it the "9000" moniker a bit premature, though... what about when you add a better tensioner? You can't just START at 9000... that causes the "It's over 9000! That's impossible!" dilemma when you add a simple feature (Like brass trim.) and call it the "9001"

  • It needs some brass trim. Nothing says "Leet construction skillz" like wood with brass trim.

    Think the Time Machine H.G. Wells built in "Time After Time" (Best time travel film ever!) It was all kinds of fancy and ornate!

  • I've been toying with the idea of making a programmable coil winder, but wasn't sure how to control the back-and-forth movement of the wire. A servo is just the thing, thanks for the idea!

  • Couple of questions:

    1) it seems that if the thread jammed, the torque from the steppers would be sufficient to end up bending the cardboard. Do you do current sensing on the steppers to try and figure out a jam ? 2) Can the cardboard slide out of the two holders, or is the interference fit enough to hold it, you were able to slide it in pretty easily.

    If you do a lot of this type of stuff, maybe a new title, toolmaker, http://en.wikipedia.org/wiki/Tool_and_die_maker . My dad was one, but he basically made fixtures and jigs out of steel.

    • Answers:

      1) The cardboard does not bend, it's pretty well supported by the holders. The thread would have to rip right down the center to damage the cardboard and I don't think it is strong enough to do that. The steppers just sit there and jitter. I could have added a 'jam detector' by checking to make sure the count was increasing as the motors were running, but I didn't. Mainly because it isn't a big deal. If there is a jam, the motors just bounce back and forth until the user tugs the thread a bit. Simplicity was my goal.

      2.) There is enough friction top hold the cardboard in. If they wear out over time, there are two hooks on each holder to attach a rubber band.

    • There doesn't really seem to be anywhere for the thread to jam except for on the source reel itself. And then you have the Rube Goldberg array of tensioner ... tentacles... and the emergency stop button. But yeah, if that wasn't stopped, it could bend the cardboard. Resulting in a "Bad one". Eh. That happens. Clear the jam, finish the wind... toss the bad one in the "Dings and dents" box and move on.

      One nit? The emergency stop button should be red. That's like... an international standard.

  • My math says 60 turns times 5 inches per turn is 25 feet. Did I miss something?

    • I'm not sure how I worded it and I'm not going to go back and check, but Robert is correct. I don't actually remember filming any of that because I don't like cameras pointed at me. I think I was blacked out for the entire shoot.

    • Yeah, I think the height of the 'bobbin' is 5", therefore a full turn would be both sides, which would be 10". 60 full revolutions at 10" each equals 50'. bam.

  • Wow, this is awesome. I'm currently a MechE student, with a side interest in programming/electronics/mechatronics, so it's really cool to see things like this combining all of those different areas in a way that can solve a very tangible problem. I look forward to seeing more videos and designs of these types of things as they are made! It's really an inspiration to keep going with the studies.

  • I made something similar for my wife a long time ago when she had a project that required dividing skeins of yarn into equal thirds. No 3d printing or laser cutting, just hardware store parts. No dual stepper motors, just hand cranked. No arduinos, just a decade counter/7-segment decoder IC. Did use a hall effect sensor though. Kids these days.

    Now, if version 2.0 could change the spool without operator intervention, I might forgive the overkill :-)

  • Why 2 stepper motors? Was more torque required?

  • Just out of curiosity, why not count the number of revolutions by storing the number of 'steps' transmitted to the motor, then dividing by the number of steps per rotation, instead of using an external hall-effect? I suppose it would be more prone to error...

    • Correct. Sometimes the steppers jitter because the conductive thread is VERY coarse and prone to jamming. It's actually coarse enough to cut through the eyelet on the feeder/distributor servo over time (or prison bars). That's why I used two steppers. At times, even those two large ones are not strong enough.

      • It seems to me the eyelet under the most stress is the one on the servo that does the final wind. Consider switching to a ceramic fishing rod eyelet.

  • When I saw 2 arduino, I immediately said "WTF 2 arduino!!". Then I thought about it. 2 arduino = it's simple and it works (KISS). Sometimes you need to get sh * t done! That is something I just recently realise. You can do something that is elegant, well thought out and your proud of it or something totally trash but works like the elegant version. I also like the saying "if you do something, do it right the first time" Like Paul said, he could of done that with one arduino. You think about it for 10 min and then code it. That would of require a little bit more time and debugging.(depending of skill) In my case, I would of tie the hall effect and e-stop to both arduino interrupts. The e-stop raise a flag and the half effect ++ counter.

    • plus, it's not like we don't have a ton of pro-minis sitting around waiting to be used... people forget, we make these a thousand or so at a time. we have a couple to spare.

      • No kidding. Two probably fell out of the bag by mistake... "Eh! I'll just use two! Easier than putting one back in the bag."

  • Nice. And varying the speed of the main motor could almost eliminate the pulsating draw of the thread.

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