USB lucky cat



  • I've had for quite some time a small Chinese (or Japanese or whatever -- yeah, I'm culturally appropriating like there were no tomorrow...) "lucky cat" figurine on my desk, or "Maneki-neko" to give it its proper name (at least so says the Mighty Wiki). Something like that:

    I quite like it (I know many people would get annoyed by the perpetual movement, but I actually quite like it...), but the one I've got is battery-powered and I'm bored with changing the battery every time and again. Since it's sitting next to my computer, there is a ready power-source nearby, so why not use it? (I'm dubious about the solar-powered ones, my desk probably doesn't get nearly enough light for that!)

    Therefore, I am looking for the same gizmo, but USB-powered. And I can't find it :-( Halp plz!

    I'm looking for something cheap, the one I've got is a cheap flimsy plastic-y thing that probably cost 10 USD or so, there is no way I'm going to spend many more than that.



  • @remi Why don't you build your own? Take a USB cable, connect the proper resistor to the wires on the other end to get the current to flow and then use a simple voltage regulator to downstep the 5 V to whatever the gizmo needs.


  • sockdevs

    @remi said in USB lucky cat:

    I've had for quite some time a small Chinese (or Japanese or whatever -- yeah, I'm culturally appropriating like there were no tomorrow...) "lucky cat" figurine on my desk, or "Maneki-neko" to give it its proper name (at least so says the Mighty Wiki). Something like that:

    I quite like it (I know many people would get annoyed by the perpetual movement, but I actually quite like it...), but the one I've got is battery-powered and I'm bored with changing the battery every time and again. Since it's sitting next to my computer, there is a ready power-source nearby, so why not use it? (I'm dubious about the solar-powered ones, my desk probably doesn't get nearly enough light for that!)

    Therefore, I am looking for the same gizmo, but USB-powered. And I can't find it :-( Halp plz!

    I'm looking for something cheap, the one I've got is a cheap flimsy plastic-y thing that probably cost 10 USD or so, there is no way I'm going to spend many more than that.

    question..... does it take one battery, or two?

    because if it takes three you can hack the end off a USB cable and wire it into the battery terminals, plug her in and you're golden. 5V is close enough to 4.5 volts that is nominal for 3x alkaline batts (and they tend to start a smidge north of that for brand new batteries anyway)

    you could also get a dc/dc stepdown converter from 5V to 1.5v for real cheap and solder that in place.

    i've googled around and it doesn't look like there's much in the way of ready made.... unless you want it to be solar powered instead. they have that: https://smile.amazon.com/Bringer-Luck-Japanese-Waving-Powered/dp/B0026NEIQQ



  • @Rhywden said in USB lucky cat:

    @remi Why don't you build your own?

    That is... tempting! Although I have absolutely 0 knowledge of anything electronic, so I'm not sure how I would wire that, but it seems straightforward enough to give it a try (and if it only costs a couple of bucks, I wouldn't mind if I blew it up doing it...)

    @accalia said in USB lucky cat:

    because if it takes three you can hack the end off a USB cable and wire it into the battery terminals, plug her in and you're golden.

    It takes only one, but I've noticed that some cheap batteries that deliver closer to 1.2 V than 1.5 V do not work, so I'm guessing that it would work better with a bit more juice. I don't know if 5 V would blow up something inside it, but again since it's a cheap gadget I wouldn't really care. So I might try that first.

    Let's find an old unused USB cable and a wiring diagram!



  • @remi said in USB lucky cat:

    Let's find an old unused USB cable and a wiring diagram!

    Assuming a regular 4-pin USB thingy, it's the outer two pins you want (the middle ones are data). I forget which way round the 5V and 0V are though.



  • @RaceProUK said in USB lucky cat:

    I forget which way round the 5V and 0V are though.

    It's a DC motor, so they go whichever way round that makes the arm swing in the direction you want it to swing.



  • @anotherusername said in USB lucky cat:

    @RaceProUK said in USB lucky cat:

    I forget which way round the 5V and 0V are though.

    It's a DC motor, so they go whichever way round that makes the arm swing in the direction you want it to swing.

    Thinking about it more, it might not actually matter: the arm will oscillate the same whichever way the motor turns.



  • @RaceProUK Depends on how the arm is connected to the motor.

    edit: does it go all the way around, or just bob up and down? In the latter case it probably wouldn't matter.



  • @anotherusername IME, the arms oscillate; I've never seen one where they go the full 360



  • @RaceProUK I was thinking of taking an old mouse or keyboard or other stack of USB peripherals that I'm not using and hacking the cable, but if I find a real cable I could try using the plug directly, that would avoid cutting it (although looking at the plug, I don't quite see how to wire into it without breaking it...).

    Also, I'm not sure whether the direction of the current would matter. I don't know what's inside the plastic but I'm guessing the cheapest possible electric motor, if I remember my school days reverting the current would just change the direction of spin (and increasing it would just increase the spin -- might be funny to put 5V instead of 1.5V and see it wave like crazy!). But since the rotation is somehow transformed into back and forth, there may be a plastic bit in there that only works if the motor spins in one direction...



  • @anotherusername @RaceProUK Yeah, the arm oscillate back and forth. I'd put a video but I have no idea how to get it from my phone to here and I'm lazy, so you'll have to take my word for it.

    I don't think the direction/voltage really matters, except that being cheap stuff that already randomly decide from time to time to not-work, anything outside of normal specs might not work for... random reasons.

    Damn it, I haven't got any spare USB stuff at my desk. That'll have to wait tonight when I come back home... (well, I haven't got any tools either, anyway...)



  • @remi Things like those are often built as simply as possible, with the cheapest components that don't immediately self-immolate, so it'll be a DC motor and a simple plastic mechanism with about three or four parts, if that. So, in theory, it shouldn't matter which way you apply the voltage.

    Beware though: if you push the full 5V through, the arm may move considerably faster than you think ;)



  • @RaceProUK Yeah, I'm counting on that (cheapest stuff being devoid of any protection and thus accepting input way out of specs without blowing).

    I don't know how fast I should expect it to wave. What is the relationship between input voltage and rotation speed for this kind of motor? If it's just linear, putting about 3x more would make it wave 3x faster, probably not quite fast enough for real lulz...



  • @remi For a cheap-ass basic DC motor, I'd assume linear, but the only way to be sure is to actually try it ;)



  • @remi said in USB lucky cat:

    But since the rotation is somehow transformed into back and forth, there may be a plastic bit in there that only works if the motor spins in one direction...

    If you hold it upside down, does the arm still move?


  • Impossible Mission Players - A

    @RaceProUK said in USB lucky cat:

    @anotherusername IME, the arms oscillate; I've never seen one where they go the full 360

    :eek: That would be even more freaky!


  • sockdevs

    @remi said in USB lucky cat:

    Let's find an old unused USB cable and a wiring diagram!

    black = negative (ground), red = positive, green and white are data and can be ignored.

    unless you have a really asshat cable manufacturer

    @remi said in USB lucky cat:

    I wouldn't mind if I blew it up doing it...

    5V is unlikely to do so. it might let the magic blue smoke out, but that's it. if you want big bada boom hook it up as the resistor in a pinch. then set it off. if the multi kVA arc doesn't destroy it the emp will werck havoc on it. :-)



  • @anotherusername said in USB lucky cat:

    If you hold it upside down, does the arm still move?

    No. If I wiggle the arm a bit, it sometimes doesn't move either. So I wouldn't assume anything about the motor from the upside-down test, it's really a cheap gadget...



  • @remi Sounds like a simpler mechanism than I thought: it sounds like it's just a cam on the motor pushing a thingy that moves the arm.



  • @accalia said in USB lucky cat:

    black = negative (ground), red = positive, green and white are data and can be ignored.

    Thanks!

    @remi said in USB lucky cat:

    I wouldn't mind if I blew it up doing it...

    5V is unlikely to do so. it might let the magic blue smoke out, but that's it.

    I was speaking figuratively about "blowing". I am certainly not expecting anything dramatic. There is no way you can make anything dramatic with such a flimsy thing.



  • @remi said in USB lucky cat:

    @Rhywden said in USB lucky cat:

    @remi Why don't you build your own?

    That is... tempting! Although I have absolutely 0 knowledge of anything electronic, so I'm not sure how I would wire that, but it seems straightforward enough to give it a try (and if it only costs a couple of bucks, I wouldn't mind if I blew it up doing it...)

    @accalia said in USB lucky cat:

    because if it takes three you can hack the end off a USB cable and wire it into the battery terminals, plug her in and you're golden.

    It takes only one, but I've noticed that some cheap batteries that deliver closer to 1.2 V than 1.5 V do not work, so I'm guessing that it would work better with a bit more juice. I don't know if 5 V would blow up something inside it, but again since it's a cheap gadget I wouldn't really care. So I might try that first.

    Let's find an old unused USB cable and a wiring diagram!

    If you want to do a nasty bodge then a silicon diode will drop about 0.5V-0.7V. So you can string 5 of them together to get somewhere in the ballpark of where you need to be. Something like a jellybean 1N4004 (or 1N400[1]-[10] or practically anything....).

    Have a high quality schematic :)

    0_1483549268029_highqualityschematic.png



  • I think you want this. US$1.76 including shipping.



  • @remi said in USB lucky cat:

    @anotherusername said in USB lucky cat:

    If you hold it upside down, does the arm still move?

    No. If I wiggle the arm a bit, it sometimes doesn't move either. So I wouldn't assume anything about the motor from the upside-down test, it's really a cheap gadget...

    I'd expect it to be one of two different designs, and given that the arm doesn't move when it's upside down, probably the first one:

    0_1483549283263_upload-2dfd664f-f5b3-4eca-8cdd-d3f85dfe7766


  • sockdevs

    @Cursorkeys said in USB lucky cat:

    If you want to do a nasty bodge then a silicon diode will drop about 0.5V-0.7V. So you can string 5 of them together to get somewhere in the ballpark of where you need to be. Something like a jellybean 1N4004 (or 1N400[1]-[10] or practically anything....).

    huh....

    let's see.... 5v to 3.3 ish would be.... 2 or three of those.... and i can get a hundred for a buck....

    hmnmm heat dissiaption shouldn't be an issue......

    /me puts in a bid



  • @accalia said in USB lucky cat:

    @Cursorkeys said in USB lucky cat:

    If you want to do a nasty bodge then a silicon diode will drop about 0.5V-0.7V. So you can string 5 of them together to get somewhere in the ballpark of where you need to be. Something like a jellybean 1N4004 (or 1N400[1]-[10] or practically anything....).

    huh....

    let's see.... 5v to 3.3 ish would be.... 2 or three of those.... and i can get a hundred for a buck....

    hmnmm heat dissiaption shouldn't be an issue......

    /me puts in a bid

    Exactly, I have a few commercial designs in production that use diode droppers. It's messy and inelegant but sometimes the price point is (nearly) the only thing that matters and crappy diodes are essentially free in volume. It is nice and reliable though, the same diode won't move very much with current or temperature.

    Those are 1A diodes though so I wouldn't exceed that. Sometimes you can have dissipation issues well inside the current rating (SOA).



  • @remi Is there actually a motor? Do you hear a whine or is it dead silent? It could easily just be a coil pulsing a magnet on a pendulum.



  • @flabdablet said in USB lucky cat:

    @remi Is there actually a motor? Do you hear a whine or is it dead silent? It could easily just be a coil pulsing a magnet on a pendulum.

    That's what I always thought these things did, have some kind of magnet and a pendulum.


  • mod

    I love you guys :D



  • @Cursorkeys said in USB lucky cat:

    Those are 1A diodes though so I wouldn't exceed that.

    Could just put them in parallel too. Even for charging, USB isn't supposed to provide more than 1.5A.



  • @anotherusername said in USB lucky cat:

    Could just put them in parallel too. Even for charging, USB isn't supposed to provide more than 1.5A.

    If that's the case, it makes me wonder why I bother to get 2.1A chargers.



  • @heterodox devices might still be able to take advantage of the extra current to charge faster if the charger will supply that much.


  • sockdevs

    @Cursorkeys said in USB lucky cat:

    @accalia said in USB lucky cat:

    @Cursorkeys said in USB lucky cat:

    If you want to do a nasty bodge then a silicon diode will drop about 0.5V-0.7V. So you can string 5 of them together to get somewhere in the ballpark of where you need to be. Something like a jellybean 1N4004 (or 1N400[1]-[10] or practically anything....).

    huh....

    let's see.... 5v to 3.3 ish would be.... 2 or three of those.... and i can get a hundred for a buck....

    hmnmm heat dissiaption shouldn't be an issue......

    /me puts in a bid

    Exactly, I have a few commercial designs in production that use diode droppers. It's messy and inelegant but sometimes the price point is (nearly) the only thing that matters and crappy diodes are essentially free in volume. It is nice and reliable though, the same diode won't move very much with current or temperature.

    Those are 1A diodes though so I wouldn't exceed that. Sometimes you can have dissipation issues well inside the current rating (SOA).

    meh. the project i'm thinking of is a 2Dcell powered application that according to my multimeter pulls about 300mA peak and seemst o hver around 200mAish


  • sockdevs

    @anotherusername said in USB lucky cat:

    @Cursorkeys said in USB lucky cat:

    Those are 1A diodes though so I wouldn't exceed that.

    Could just put them in parallel too. Even for charging, USB isn't supposed to provide more than 1.5A.

    USB 1.0 spec was that yeah. they raised that for USB2, and USB3/3.0b/3.1/thunderbolt has current/voltage negotiation up to IIRC something like 20V/5A



  • Considers quickly making a application that puts an animated Maneki-neko in the system tray

    ....

    ...

    ...

    Nah.



  • @accalia said in USB lucky cat:

    USB 1.0 spec was that yeah. they raised that for USB2, and USB3/3.0b/3.1/thunderbolt has current/voltage negotiation up to IIRC something like 20V/5A

    Oh, is that how the Google Pixel phone is doing the 20 minute charge or whatever the hell it's advertising?


  • sockdevs

    @heterodox said in USB lucky cat:

    @accalia said in USB lucky cat:

    USB 1.0 spec was that yeah. they raised that for USB2, and USB3/3.0b/3.1/thunderbolt has current/voltage negotiation up to IIRC something like 20V/5A

    Oh, is that how the Google Pixel phone is doing the 20 minute charge or whatever the hell it's advertising?

    it's also how you can use it to charge other usbC devices. :-D



  • @accalia said in USB lucky cat:

    @anotherusername said in USB lucky cat:

    @Cursorkeys said in USB lucky cat:

    Those are 1A diodes though so I wouldn't exceed that.

    Could just put them in parallel too. Even for charging, USB isn't supposed to provide more than 1.5A.

    USB 1.0 spec was that yeah. they raised that for USB2, and USB3/3.0b/3.1/thunderbolt has current/voltage negotiation up to IIRC something like 20V/5A

    I think the page I found said it was 500mA for USB 1, 1.5A for USB 2. Dumb devices can't negotiate to ask for anything higher, so I believe even under USB 3 they'd still theoretically be limited to 1.5A, assuming everybody's following the spec strictly (they're often not).


  • sockdevs

    @anotherusername said in USB lucky cat:

    Dumb devices can't negotiate to ask for anything higher, so I believe even under USB 3 they'd still theoretically be limited to 1.5A

    i to believe the 3.1 spec says the default is 1.5A until negotiation occurs.



  • @anotherusername said in USB lucky cat:

    @Cursorkeys said in USB lucky cat:

    Those are 1A diodes though so I wouldn't exceed that.

    Could just put them in parallel too. Even for charging, USB isn't supposed to provide more than 1.5A.

    They're dynamic not purely resistive so that doesn't tend to work very well. There will be some current sharing but best-case it is usually under 50% until overheating of the active area on the device with the lowest forward voltage causes the next device to take over then it too overheats and the behaviour repeats ad nauseam until failure.
    You can current-share properly on semiconductors but that requires active servoing or techniques like emitter degeneration (which is just passive servoing really) to encourage them to share the load better.



  • @flabdablet said in USB lucky cat:

    @remi Is there actually a motor? Do you hear a whine or is it dead silent? It could easily just be a coil pulsing a magnet on a pendulum.

    That is a very good point and that I didn't think of that show how n00b I am when it comes to hardware... No, there isn't any noise so definitely not a motor!



  • @Zecc said in USB lucky cat:

    Considers quickly making a application that puts an animated Maneki-neko in the system tray

    ....

    ...

    ...

    Nah.

    Yeah, make one for that new Apple emoji keyboard thingy.



  • So, armed with a few tools and my non-existent DIY skills...

    The poor beast, happily waving and blissfully ignorant of what's going to happen to it...
    0_1483565908223_IMG_0214.JPG

    Stripping a USB cable (these tiny wires are definitely not made to be stripped...). I get almost 6V, and it fluctuates quite a lot. I guess that's because of the flimsy connection where everything had to stay in place while I was taking the picture?
    0_1483566225039_IMG_0212.JPG

    And finally, after somehow fixing the wires inside... IT'S ALIVE!!!
    0_1483566195363_IMG_0213.JPG

    It does not seem to wave much faster than before, but it waves much more strongly, so now I get an annoying noise of the arm hitting the plastic casing at the end of its course. I had that with some very charged batteries as well and I did get rid of it with a bit of paper strategically located in the casing, I'll have to try that again (when I've secured the contraption and put it on my desk).

    All in all, a rather successful operation, I'd say.



  • @boomzilla said in USB lucky cat:

    @Zecc said in USB lucky cat:

    Considers quickly making a application that puts an animated Maneki-neko in the system tray

    ....

    ...

    ...

    Nah.

    Yeah, make one for that new Apple emoji keyboard thingy.

    Don't be ridiculous. That's for Nyan Cats.

    Edit: having said that, if you buy me one of those laptops I'll do it.



  • @remi said in USB lucky cat:

    now I get an annoying noise of the arm hitting the plastic casing at the end of its course.

    A liberal helping of gaffer's tape inside the arm socket later, and the noise is gone.

    I am now waiting to see if anyone will notice the new cable and comment on it...


  • Winner of the 2016 Presidential Election

    @Zecc said in USB lucky cat:

    Considers quickly making a application that puts an animated Maneki-neko in the system tray

    WHAARGARBL NO SUCH THING YOU MEAN NOTIFICATION AREA



  • Mrs wft has got a solar powered thing as a gift from her friend. When I turn on the lights in the room, it wags its hand like mad. Even on gloomy winter days, there's a bit of movement. I call it a "buddha cat" for no good reason, there is something buddhish about the thing. Maybe I'll use it for self-hypnosis one day or something.

    Seen once another solar-powered cat in a car. Man, I tell you it was laaaarge. It was at the back of the car, waving its blessing at the poor souls who happened to drive behind it. Like the pope.

    But the thing I'm gonna tell you, don't you dare diss solar power.

    Also, it won't bring you luck, you're better off with some lottery once in a while.


  • Discourse touched me in a no-no place

    @anotherusername said in USB lucky cat:

    edit: does it go all the way around, or just bob up and down? In the latter case it probably wouldn't matter.

    0_1483619211446_6qb0ro.gif



  • @anotherusername said in USB lucky cat:

    @Cursorkeys said in USB lucky cat:

    Those are 1A diodes though so I wouldn't exceed that.

    Could just put them in parallel too. Even for charging, USB isn't supposed to provide more than 1.5A.

    Putting voltage-dropping diodes in parallel is not wonderful design. No two diodes will have the knee of the V-I curve in exactly the same place, so in a pair of parallel diodes you'll often find one of them carrying the lion's share of the current.

    With (claimed) 96% efficient switching converters available for under two bucks, there's really very little reason to go the bodge instead.



  • @remi said in USB lucky cat:

    I get almost 6V, and it fluctuates quite a lot. I guess that's because of the flimsy connection where everything had to stay in place while I was taking the picture?

    I'd guess it's because you're measuring the output of a tiny switching regulator under no-load conditions. Many switching designs have trouble maintaining regulation until something like 5% of their design maximum current starts being drawn from them.



  • @remi said in USB lucky cat:

    It does not seem to wave much faster than before, but it waves much more strongly, so now I get an annoying noise of the arm hitting the plastic casing at the end of its course.

    That lends support to the pulsed-pendulum hypothesis.

    If you want it to wave at you rather than bat frantically at invisible moths, you should probably incorporate the switching regulator I linked above to drop the supply voltage back to the 1.5V the machine was designed for.


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