EEVblog #435 - 3D Rocker Teardown

You know you want to see what's inside a 3D Rocker Platform.

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[rarbiart]

instead of a portable scope the alternative would have been to feed the DUT via an insulating transformer. (this was the basic bench equipment of all radio repair men in the tube eara.)

[krokodyl]

I can easily see how it could be useful in my 'lab' - rocking container with PCB and etching solution

[EEVblog]

Yep, good idea, if I still did that :-> I'd expect a bubble tank to be superior to a rocker though.

[flex]

The arm thing at 3:53 keeps the platform from spinning around.

[ElectronicTonic]

To reiterate what Mike said, yes it's a shaded pole motor. The iron core has two closed copper loops (the shading coils) to offset the phase of the alternating magnetic field through a portion of the iron core next to the rotor. The only purpose of the shading coils is to set the rotor spinning on its own. This type of motor is common in old record players and small household fans and fans inside appliances like microwave ovens.

[mikeselectricstuff]

Put the camera on it. Suck on that, image stabilisation!

[drews]

The arm is to stop the deck rotating, with rubber bushes to allow flexibility (not for vibration isolation) and the shaft coming out of the worm drive gearbox is just an angled coupler ;)

[patitoiuionutcatalin]

One such tool is used when testing measuring instruments subjected to oscillatory motion in 3 dimensions, used in avionics instruments or those that are boarded on ships; all on such a unit are tested and surveying instruments especially theodolites to measure decentering of optical components

[beou]

It will be EXTREMELLY interesting if sometime Dave and Mike had a teardown together!!!
Dave and Mike, have you ever condiser traveling to UK or AUS respectively for a magical teardown?? :)

[EEVblog]

I was thinking that, a shaker cage. But it's gotta go really fast for that...

[Tardymo]

When Dave showed how the rocking motion is happening at mark 02:54, my first question was - what keeps platform from rotating around? When metal arm was shown, it was clear. Strange that Dave did not figure it out immediately.

[EEVblog]

Notice how the corners move vertically? ;-)

[EEVblog]

Yes, sadly it just ain't going to be possible to go any faster with the existing shaded pole motor and reduction gearbox. Oh well, worth having a look.

[aptsys]

Any load on any circuit in the house including the scope itself!) will cause the imbalance easily as there will now be two parallel paths from phase to the star point assuming you have a low enough Zs. Monkeh is correct.

[EEVblog]

I've done one tracing down a short on my CanyonCopter.

[mikeselectricstuff]

that's a shaded-pole motor - there is no permanent magnet - it works by eddy-currents in the rotor

[aiden]

They are. I used to hand agitate, but when I built my etching tank I put in a heater and bubbler and I could get a decent sized board done in about 10 min.

[ExStaticBass]

Those are actually great for etching PCBs mate. Think about the swirling motion of the etching solution over the copper clad board... Just pop in a pyrex or simillar deep walled glass tray and bammo. Perfectly etched board with uniform and fast etching.

[StuartYoung]

Got some etchant? Get a large plastic (tupperware) container with a lid, put in a PCB held off the bottom of the container a few mils so you get a gap under the PCB, and then put in just enough etchant to cover the middle of the board when sitting on the platform. Put a cover on the container and turn it on. Keeps the etchant moving so you'll probably etch a PCB quite quickly!

[trombonista]

if you were to fill in one every second space on that calibration wheel with a black marker wouldn't it spin at double the speed??? (and so on for any other fraction)