EEVblog 1485 - PedalCell CadenceX Bike Generator LOL FAIL!

The failed PedalCell CadenceX Bike Generator from the previous mailbag video is tested, torn down, analysed, hilrariously laughed at, and dodgily repaired.

00:00 - Failed Pedalcell generator - getting the pinout
02:00 - The PCB
02:40 - Oscilloscope rotation test
03:45 - Dremel speed Captain!
04:22 - Generator teardown
05:32 - Hmm, what's going on with these stator coils
06:00 - Hall effect sensors
06:58 - A-HA Gotcha. These magnets make no sense at all!
08:47 - Someone skimped at the glue factory
11:27 - It's just a BLDC Brusshless DC motor being used as a generator
12:48 - Nothing that can't be fixed with some epoxy
14:00 - Vrooooom!

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#ElectronicsCreators #FAIL #Pedalcell

[Vishmoney]

Huge fan of your channel! How I learned all of my EE fundamentals. I’m actually the engineer that designed the electronics. Would love to chat more

[ashleywest]

It's a sensored brushless DC motor being used as a generator. They are commonly used in upmarket RC cars as the sensors give good starting torque. Chinese made ones are known for losing their magnets. We use unsensored ones in RC planes and were in the habit of pulling them apart when new and super gluing the magnets in properly before first use.

[HwAoRrDk]

I noticed from the previous Mailbag video the "do's and don'ts" sheet included in the box said "don't ride over 40 mph". I guess they already realised that excessive speed was a failure mode for the generator! But simply telling your users not to ride too fast isn't really a proper solution to poor manufacturing...

[conwaylai]

When I was working in a tape drive manufacturer, we were surprised that the failure from the drive unit were so high. Went down to the factory in China, and after some auditing; the operators were not curing the loctite glue under the UV lamp (they just dab the glue and move it along). Apparently, no one understood the process instructions, so that part was not translated to mandarin for the operators.

[xjet]

That's what's called an "inrunner" configuration (where the magnets are on the rotating shaft). They can fly apart as this one did. The other configuration (where the magnets are on a rotating bell and the coils are mounted in the middle) is called an "outrunner". The benefits of the outrunner include the fact that the magnets are being flung in-place by centrifugal force when things are turning. They still throw magnets sometimes however -- if they're poorly glued.

[johnrobholmes]

Laminations are used on the PM rotor because it's practically free to tool the lam mold to cut the stator and rotor support (back iron) at the same time. There is some amount of recirculating current in this "back iron" but laminations aren't really needed there.

[I.____.....__...__]

Well that's a shame, and a waste. The rest of it was pretty well-made, then they blew it with the very first, most fundamental, integral part in the most bone-headed way. There were so many ways they could have done that, why they went with a drop of glue, is beyond me. 🤦

[GannDolph]

I had one of those as a kid - manufactured over 50 years ago at this point

It was basically a perm magnet brushed DC generator (motor) you'd wire directly to the lamp module which contained a standard torch bulb (6v as I recall) . There was only one wire - they grounded by clamping down and gashing thru your paint to the bike frame. The on off switch was simply the mechanical lever that would engage/disengage the drive cog against the side of your tire.

It had horrible magnetic cogging and placed a surprising load on the wheel which you could really feel . The light intensity would go up and down as you peddled and went off when you stopped. No capacitors or batteries or regulators. It ran quite dimly most of the time, to leave some headroom in case you went really fast so it wouldn't blow the bulb..

[MrSnoots]

"someone skimped at the glue factory" made me laugh out loud. I just imagine someone at an actual glue factory being pissed because someone at a janky motor/generator factory did a shit job.

[byronwatkins]

Nice catch, Dave! This was never destined to be reliable as a motor either. Adhesive doesn't stick well to ceramic magnets... especially under tension. I would have wrapped the ends of the magnet assembly with a few turns of fine wire and covered that with adhesive. Even better would be to specify grooves to fit the wire.

[caerffili_callin]

These type of products are popular among long distance touring cyclists who may not have access to mains electricity to charge a lower bank up. Usually the electronics is connected to an already installed hub dynamo on the front wheel, but they have become very expensive and I assume this product was designed to be a lower cost easily removable alternative.

[SianaGearz]

Germans formed a "Forumslader" enthusiast working group decades ago, because any attempts at electronics coming out of bicycle accessory companies were garbage. Their DIY series of devices have several design goals. Main is compliance to legal norms - you simply HAVE to have dynamo lights in Germany, so you don't ever run out of energy. When you do, it's nice to be able to run them independently of pedalling, to give you extra safety when you need it, so they added hold up power which can be activated manually. Also they made it stealthy, you hide it entirely in the frame, so the authorities don't go around questioning you and people aren't so inclined to nick your stuff. Plus you get the ability to top up your GPS (this is when the project started, before smartphones were around) and phones and gadgets. Many members go on bicycle tours hundreds of km with intermittent camping and whatnot, and having true energy independence is great for a peace of mind. Then of course they got carried away and added Bluetooth and whatnot, which is nice as well, people love their bicycle tachos, but they are a little finicky, and the hub dynamo gives you regular pulses anyway.

You've got to use an actual bicycle quality dynamo to get that power. Tyre side dynamos work but aren't entirely pleasant. Hub dynamo is fairly nice though, and when it's shorted out, you can barely feel it at all, and those are reliable, they'll last for decades. That's the one sort of part you want from bicycle parts companies where they know what they're doing and are held to relevant standards.

[shreddder]

Perhaps it could wirelessly transmit the power to the grid through the solar roadways.

[pauldeboer]

In hindsight it shouldn't feel smooth as silk when you rotate it I guess. Also when you opened it I noticed the strange distribution of the magnets with a gap between 2, see @5:41. That should have been a clue what happened but I didn't get it either until you got one of the magnets out. I wonder if there are different forces in play when it is used as intended, eg as a motor. Not sure, more coffee needed.

[harshbarj]

$299 for what's incorrectly called a "bottle dynamo" (All that I have seen are actually generators as they produce AC, not DC). I paid $80 for my Sturmey archer generator hub with built in break. For less than $50 I could easily add a battery pack and get the same thing as this. As a bicycle commuter having always on light is great and having them powered by a generator mean never worrying about batteries.

[mikeselectricstuff]

I wonder if the hall sensor is so they can adjust the charge current depending on speed

[TD.SteveArcs]

I remember seeing a "dynamo" on my grandfather's bike as a kid, I asked him about it and he said "oh that thing !" "It just makes it harder to peddle, they don't use them anymore now we have good batteries available" that was in 1987 😅

[volvo]

Almost makes me wonder if the company used a bunch of discount known bad motors as generators thinking they'd suit... What an odd failure and a crappy design, that motor does not look like it would have survived high speed rotation either way...

[mosfet]

It only takes one magnet to come lose and stick to the coils. Once that happens it jambs the whole motor up and then all the rest of the magnets break loose. The magnets change polarity from one to the next - NSNSNS. You can use a spare magnet to get the orientation, it doesn't matter if it N or S just as long as they run opposite from one to the next.

[yowieP]

Found this problem a number of times Dave in model aircraft motors its quite common for the magnets to let go.