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Accidentally killed my King Song !?


edwin_rm

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The fuses must be of very low quality if AliExpress is selling them for only cents! It would be nice to eventually replace them with something of a very high quality.

Anyways, the following picture better explains what happened. I didn't just let the wheel drop normally down the stairstep, I first lifted the wheel by holding the fully extended handle, which is what caused it to act like an angry dog when I placed on the step below. The extended handle meant I couldn't stabilize it, making a forced brake necessary  for me to stop the spin.

I ride down stairsteps all the time. It is no problem, as it is a just drop rather than a lift. It doesn't accelerate much if you just drop down a stairstep instead. Lifting it a little made it spin too fast. I should have rolled it down the stairstep instead. Lesson learned.

dog-lead_2705256b.jpg

Imagine the dog is the KS16, and the leash is the extended handle. ;)

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Ah I got it. The dog sees a cat and starts running at top speed, but the leash is more of a slip knot and kkkiee the dog blows a fuse and passes out from being stopped suddenly.  I've done that to my NB1E+, but luckily all I got was a squelch against the concrete.  

Does the current spike quite high if the wheel is spinning very quickly and then forced to stop against resistance?  It would be interesting to see a voltage / current log graph of the event just to learn what is happening during the fuse blowout.  

I guess the controller detects the tilt of the case as it is lifted so it powers the motor forwards.  When the wheel meets the ground it detects that the resistance is slowing the speed of the wheel so it applies more power to increase torque to stay balanced just as if you were riding on a flat area and then hit a sudden hill it needs more power to climb, but in the current situation it is brought to an abrupt stop that draws too much current which blows the fuse to protect the MOSFETs.

I wonder what the solution to something like this would be.  Maybe some sort of weight detector might keep speeds low and prevent high current draws or a switch that detects if the handle is deployed to keep speeds low?  In @Cloud's situation where the wheel is stuck underneath something I wonder whether there is any way to detect that.

Regarding people doing 180's they don't really brake but quickly change the tire's direction so maybe the current just changes direction quickly without any peak changes in amplitude?  Again it would be nice to see some more data logs.  I wonder if it would be like quickly swapping the voltage poles on an electric motor - it just flips direction and goes the other way...

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20 hours ago, edwin_rm said:

The fuses must be of very low quality if AliExpress is selling them for only cents! It would be nice to eventually replace them with something of a very high quality.

The fuse is over hundred years old technology and any "very high quality" ones you'd attempt to purchase anywhere would be most likely from the very same batch as the ones on aliexpress just re-packaged ;)

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42 minutes ago, HEC said:

The fuse is over hundred years old technology and any "very high quality" ones you'd attempt to purchase anywhere would be most likely from the very same batch as the ones on aliexpress just re-packaged ;)

Sometimes  yes, but sometimes no. For example, if you buy a Littelfuse fuse the chances are that they have quality control and pull samples for testing to ensure they are within specs on the data sheet. There could be no-name ones made in the same factory with the same look and shape, but with a fuse alloy of questionable origin that doesn't meet the same specs. Or they might even be rejects that Littelfuse wouldn't accept because spot checks found problems. Unless the company ensures they're destroyed, the factory can sneak them onto the black market to salvage some profit and hey, if the fuse blows well maybe it would have blown anyway. :rolleyes:

Those look like Littlefuse MINI brand fuses from the shape but the company doesn't sell them in 40A variations, the 30A is the max current. I'm wondering if the smaller MINI package should even be used for a 40A fuse, or maybe it just looks like the package but is a larger dimension. There's a larger MAXI version that supports higher currents but it's a bigger package.

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14 hours ago, dmethvin said:

Sometimes  yes, but sometimes no. For example, if you buy a Littelfuse fuse the chances are that they have quality control and pull samples for testing to ensure they are within specs on the data sheet.

Indeed however at that price you can perform visual inspection and throw away those clearly bad like imperfect casts and so on. It's a bit hard to "test" specific fuse without actually blowing it but you can sacrifice a few to see if they're within the expected specs. Even the branded ones are unlikely deeply checked one by one but instead samples are taken from each batch to ensure consistent quality.

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22 hours ago, dmethvin said:

Or they might even be rejects that Littelfuse wouldn't accept because spot checks found problems.

At least on some the components I've ordered from Aliexpress, they are clearly factory rejects... :D  Or not necessarily factory, but the customer buying them, for example, I just got a tube of MPC604's with Microchip-logos (btw, here's a good cheat sheet:  http://www.electronicspoint.com/attachments/electronic-component-manufacturer-logos-2015-01-06-002-png.17990/ ) that has "RETEST: D/C1250" -sticker on the tube :P  Don't know if that means they failed to meet some specs of the component or what, but it does make me wonder whether they're up to spec ;)

Also, a bunch of regulators I have came with lots of scratches on the backside (it was a lot of 10 or so, all them look like that), but the legs look intact etc., so probably not dismantled from some other device, but rejected by the original buyer. Sometimes you can also spot product photos showing TO-220's that have been clearly cut off from some device (the legs are just "stubs") and such... Most of the time it doesn't matter that much for my hobbyist projects, if they're (slightly) out of spec, as long as they work. Almost all of the stuff I've gotten has been pristine, seemingly original and up to the specs, but of course since I always pick pretty much the cheapest options I can find, one can expect to sometimes hit some poor quality (or even counterfeit) components ;)

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3 hours ago, esaj said:

Almost all of the stuff I've gotten has been pristine, seemingly original and up to the specs, but of course since I always pick pretty much the cheapest options I can find, one can expect to sometimes hit some poor quality (or even counterfeit) components ;)

When I did more hobbyist electronics I used to buy from companies that took excess inventory from chip makers, with no guarantee of whether they met specs or not. However, there were usually enough good ones to justify buying them and I wasn't risking my life with the projects I was building. There was even a "grab bag" that they even said included floor sweepings from the factory, it had all sorts of stuff. This was back when one good quality LED was $5 and you could get a whole bag of about 50 from these guys for $5. If you mounted 10 of them in a row you'd be lucky to find 2 that had the same brightness, but at least most of them did actually work.

EDIT: Here is one of the places I bought from: Poly Paks

 

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11 minutes ago, dmethvin said:

When I did more hobbyist electronics I used to buy from companies that took excess inventory from chip makers, with no guarantee of whether they met specs or not. However, there were usually enough good ones to justify buying them and I wasn't risking my life with the projects I was building. There was even a "grab bag" that they even said included floor sweepings from the factory, it had all sorts of stuff.

I saw a while back that some of the domestic small-time electronics companies also had those "grab bags", although I think they just contain old components from their own inventories, not necessarily factory rejects. Have to look through again those some time... ;)

11 minutes ago, dmethvin said:

This was back when one good quality LED was $5 and you could get a whole bag of about 50 from these guys for $5. If you mounted 10 of them in a row you'd be lucky to find 2 that had the same brightness, but at least most of them did actually work.

Going back memory lane, had I gotten interested in electronics back when I still was in vocational school, I wouldn't have gotten very far: the STK500-boards with something like ATMega16's we used cost something like hundred or couple of hundred euros back then... Being a poor student, I couldn't have afforded one any way :P  Nowadays, from Aliexpress I can get an Arduino Uno -clone for something like 2.50€ delivered, 5-6€ per Mega256, couple of euros for Nano... It's almost ridiculous :D  Consider that domestically, an Arduino Uno costs something like 30€, 45€ for Mega, 99€ for an Arduino "starter pack" (Uno + some components)... :ph34r:  Check out the prices and laugh your ass off:  https://www.verkkokauppa.com/fi/search?q=arduino

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