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Centrifuge strobe

  (+8)(+8)
(+8)
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This is a nichey idea, probably for an audience of 1.

In some centrifuges, the tubes are supported around their neck, leaving the body of the tube visible. This is especially true for vacuum centrifuges, which are used for evaporating liquids under vacuum (the centrifuging stops liquid from bubbling up out of the tube). In many cases, the lid of the centrifuge is transparent (or could be made so), which means you can see your tubes whizzing around.

In general, there is no advantage to being able to see the tubes whilst they whizz - they're just a circular blur. However, a xenon strobe built into the centrifuge and synced with the rotor would give you a freeze-frame view of your samples while they spin. This would be useful in determining whether, for example, your gunk has pelleted or (in the case of a vacuum centrifuge) whether you've removed enough liquid. This would save having to stop and then restart the centrifuge (which is a bad idea if you're trying to pellet something anyway).

MaxwellBuchanan, Jul 11 2019

[link]






       I thought this already existed?
xenzag, Jul 11 2019
  

       Nope.
MaxwellBuchanan, Jul 11 2019
  

       Given the usefultility of a strobe, you kind of wonder why most appliances with some rotating component do not have a strobe sync output.
bigsleep, Jul 11 2019
  

       We consider that there may be a risk of inducing epileptic seizures in unwary users and onlookers, so [+].
8th of 7, Jul 11 2019
  

       The rotation speed of the centrifuge will generally be high enough to put the strobe rate above the frequency that can trigger seizures.
MaxwellBuchanan, Jul 11 2019
  

       Yes, but that can be put right, shirley ? A hit-and-miss trigger sequence delivering a 3 to 5 Hz flash ?
8th of 7, Jul 11 2019
  

       [8th], perhaps you could just buy your own xenon tacho strobe and take it into a crowded place. In any event, please get out of my lab. And put that back.
MaxwellBuchanan, Jul 11 2019
  

       We only wanted one as a souvenir .. it's not really stealing or anything ...   

       Besides, after we took your family for a guided tour of our Cube, all sorts of things seemed to be missing. So you're hardly in a position to criticize ...
8th of 7, Jul 11 2019
  

       Ebola is not, by any stretch of the imagination, a "souvenir".
MaxwellBuchanan, Jul 11 2019
  

       Perhaps we have misunderstood "souvenir ". Everyone who's had it and survived says they'll never forget it ...
8th of 7, Jul 11 2019
  

       //rotation speed of the centrifuge will generally be high enough//
You don't need the strobe to flash once-per-rev, but you DO need the duration of the flash to be short enough to "freeze" the motion.
Eg: a 300mm diameter centrifuge doing 6,000rpm has a tip speed of 2.39m/s. To "stop" it, you would want it moving less than, say, 0.25mm; a duration of 1/10,000 of a second.
(Quick Google...)
Hmm, that's not actually too bad...
neutrinos_shadow, Jul 11 2019
  

       Quite so. A xenon strobe will handle that (just). But you probably do want one flash per rev, simply to get enough light to see the sample by.
MaxwellBuchanan, Jul 11 2019
  

       <Obligatory Chief Brodie paraphrase>   

       " You're going to need a bigger strobe."   

       </OCBp>
8th of 7, Jul 11 2019
  

       [MaxwellBuchanan]; that's 100Hz (continuing with my example values), so again not too bad. With the power of LEDs these days, I don't think "get enough light" will be a problem. I would think every 4th rev (ie: 25Hz; video frame- rate) would be plenty.
How accurately can the rpm be measured/matched?
neutrinos_shadow, Jul 11 2019
  

       LEDs might be enough, that's true. Speed sensing is not an issue. Centrifuges normally have a little magnet on the base of their drive shaft, that is sensed by a Hall-effect device and is used to regulate (and measure) speed. Just use that pulse to trigger the strobe.
MaxwellBuchanan, Jul 11 2019
  

       There is a much simpler solution.   

       Onto the top of the centrufuge shaft, place an opaque dusc with a slot in it above the position of interest.   

       Above the disc, place a bright light source in a fixed position to shine down through a fixed aperture when the two slots line up.   

       At the same point in its rotation, the moving slot will uncover the light source, illuminating the target.   

       Simple; cheap; foolproof; self synchronizing.
8th of 7, Jul 11 2019
  

       Yes, but not as cheap, simple and self-synchronising as using the already-present once-per-revolution pulse from the rotor shaft.
MaxwellBuchanan, Jul 11 2019
  

       Wouldn't a better solution be to mount a camera on the centrifuge rotor, powered by batteries and connected for video by a radio link (e.g. Bluetooth), or bothed by a rotary transformer?   

       Wouldn't the actual better solution be to use a proper analytical centrifuge that has hardware built in for quantitative measurement of the progress of your centrifugation?   

       Nevertheless, [+]
notexactly, Jul 11 2019
  

       //mount a camera on the centrifuge rotor// Cumbersome.   

       For analytical centrifuges, yes there are other better options. But a cheap, simple centrifuge (such as the centrifuge part of a vacuum centrifuge) could be so easily adapted, requiring only the use of the existing rotation sensor to trigger the strobe. We're not talking precise analytical tool here - I just want to be able to see if my gunk has pelleted, or if my sample has dried down.
MaxwellBuchanan, Jul 11 2019
  

       // I just want to be able to see if my gunk has pelleted, or if my sample has dried down. //   

       <Contemplates possible double-entendres/>   

       <Wonders how carefully [MB] considered his choice of words, if at all/>   

       <Compares text with similar stream-of-consciousness annotations/>   

       <Mulls possibility that [MB] is unknowingly channelling the spirit of James Joyce/>   

       <Decides in favour of theory that [MB] has been over-indulging in the vintage* Albanian turnip brandy again/>   

       <Sits back to await further annotations/>   

       *"None sold 'till a week old !"
8th of 7, Jul 11 2019
  

       Had you considered mounting the observer's head in the centre of the centrifuge?
pocmloc, Jul 12 2019
  

       Following [8th]'s annotation, yes.
MaxwellBuchanan, Jul 12 2019
  

       Does this open up experiments of pulsed light on reagents whilst under Gs? Because science is really good at one variable/measurable dimension.
wjt, Jul 12 2019
  

       "place an opaque dusc with a slot in it above the position of interest..."   

       Came here to day this, only with the word 'disc'. :)   

       It's a neat low tech solution. There's no sync required as the shield with the slot could just be bolted to the same assembly.   

       The strobe has some advantages though. It has the potential to be brighter. You can see multiple tubes at once. And by decoupling the strobe and the centrifuge you can rotate the image of the tubes to examine different ones; something that would be mechanincally complex with the slot assembly.
st3f, Jul 12 2019
  

       // You can see multiple tubes at once. ... examine different ones //   

       No good for [MB], then; he has trouble concentrating on even one thing at a time ...
8th of 7, Jul 12 2019
  

       As a QA guy who served five years doing inspection in the centrifuge mines, I endorse this idea. (+)
normzone, Jul 12 2019
  
      
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