Stroboscopic effect

[C JParticipant @cj88518]

I'm using a boring bar to slowly cut a custom recess into some soft jaws mounted in the three jaw chuck of my S7 and I'm gauging the end of the cut, the final diameter, by eye, but the three jaws are producing a strong stroboscopic effect at the chosen spindle speed.

So my question is has anyone considered the use of a stroboscopic lamp geared to the spindle to counteract this effect and make the workpiece appear stationary?

[C JParticipant @cj88518]

Lathe lighting

[duncan webster 1Participant @duncanwebster1]

Sounds dangerous to me!

[SteviegtrParticipant @steviegtr]

Not a good idea. That's why in industry you balance the lighting over 3 phase.

Srteve.

[Ed DuffnerParticipant @edduffner79357]

Perhaps turn a plug that is final diameter, get close by eye and then sneek up on final diameter to match the plug.

Ed.

If I remember correctly, twin fluorescent lights back in the day had lead/lag circuits utiising a capacitor in one of the lamps' circuits. This would make both circuits out of phase to each other and cancel out the strobe effect which could make rotating machinery appear stationary.

[not done it yetParticipant @notdoneityet]

Change your lighting from fluorescent to something else? That will produce the strobe problem unless you are turning the chuck at exactly the frequency your brain is computing a picture produced by the signals from your eye(s). I think most people’s brains can accommodate that scenario and avoid the effect.

If it is that particular speed, try changing it a bit? Gauge your final diameter with a go/no go plug?

Personally, I would not want any stroboscopic lamp anywhere near my work station. I have LED lamp which is on the way out and it strobes annoyingly, very occasionally. At that point it is switched off (to cool down?) and an alternative illuminator directed on the work. It would be in the bin if it were not my lamp on a PIR controller, for entry to my workshop, if I was unable to change the LED.

[old martParticipant @oldmart]

You may be able to get a led lamp which runs on a plug in transformer. Actually, I may be right in thinking that led lights do not run at mains frequency, so a led tube and starter which fit in a normal flourescent light fitting may solve the problem.

[C JParticipant @cj88518]

In an experiment, I was able to still a line of Tippex drawn on the chuck using a strobe app on my IPhone but the illumination was dependant on the angle and insufficient to overcome the spinning jaws which also reflected the light.

So while I won't pursue this idea, I found it interesting.

Edited By C J on 28/06/2020 14:38:20

Edited By C J on 28/06/2020 14:40:08

Edited By C J on 28/06/2020 14:42:33

[SteviegtrParticipant @steviegtr]

Posted by old mart on 28/06/2020 14:25:11:

You may be able to get a led lamp which runs on a plug in transformer. Actually, I may be right in thinking that led lights do not run at mains frequency, so a led tube and starter which fit in a normal flourescent light fitting may solve the problem.

Yes correct LED lights are D.C.

Steve.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Steviegtr on 28/06/2020 14:44:26:

Posted by old mart on 28/06/2020 14:25:11:

You may be able to get a led lamp which runs on a plug in transformer. Actually, I may be right in thinking that led lights do not run at mains frequency, so a led tube and starter which fit in a normal flourescent light fitting may solve the problem.

Yes correct LED lights are D.C.

Steve.

.

True … but they are also capable of very fast switching on a pulse-train : So they can make excellent strobe lights [if that’s what you want].

MichaelG.

[not done it yetParticipant @notdoneityet]

Yes correct LED lights are D.C.

MG beat me to it (by nearly an hour) but my comment was it’s a diode so will only pass current one way. and they can be switched off and on in order to flash.

I am expecting my LED is ‘going home‘ but it could be the supply. It is certainly strobing occasionally when it is warmed up. It’s a l*dl special just out of warranty.

[SteviegtrParticipant @steviegtr]

Posted by not done it yet on 28/06/2020 15:58:03:

Yes correct LED lights are D.C.

MG beat me to it (by nearly an hour) but my comment was it’s a diode so will only pass current one way. and they can be switched off and on in order to flash.

I am expecting my LED is ‘going home‘ but it could be the supply. It is certainly strobing occasionally when it is warmed up. It’s a l*dl special just out of warranty.

Yes LED is not as long lasting as 1st thought. My home is all LED lights & lots in garden for the new Koi pond. They do look good but for how long. The newer ones with the square yellow single diode seem to be better. I have a set in my van main & dip & are stunning but were very expensive. Philips items.

Steve.

[duncan webster 1Participant @duncanwebster1]

My experience, admittedly only one supplier, is that the actual LEDs are fine, it's the associated switch mode electronics that die

[Howard LewisParticipant @howardlewis46836]

There are fluorescent lights on the ceiling of my small workshop, but have never seen any stroboscopic effects, although aware that it can happen.

Maybe I don't run the lathe fast enough for it be apparent.

LEDs were used to replace C F Ls in work lights because of the same fear, but I believe that CFLs operate on a higher, internally generated, frequency..

I have had LED lamps which although emitting full brilliance, have a flicker. I put this down to a fault developing in the internal power supply, so that the LED only conducts on one half of the cycle. They were binned, since the effect was tiring on the eyes.

Howard

[Oven ManParticipant @ovenman]

Posted by duncan webster on 28/06/2020 16:25:20:

My experience, admittedly only one supplier, is that the actual LEDs are fine, it's the associated switch mode electronics that die

Duncan is absolutely correct. Interesting that that any guarantee usually says the LED is guaranteed for x years, NOT the complete lamp.

Peter

[Frances IoMParticipant @francesiom58905]

it is true that the power for small LEDs from the mains adapter is rectified supersonic frequency to allow use of a very small isolation transformer (one of mine is probably around 12kHz as I can still hear the slight buzz – however in the cheap drivers I have seen this HF oscillator is driven by a poorly smoothed rectified mains thus the HF oscillator is modulated at 100Hz and there is definitely a stroboscopic effect

Edited By Frances IoM on 28/06/2020 16:44:04

[Werner SchleidtParticipant @wernerschleidt45161]

Stroboscopic effects are dangerous, if they are synchronised to the spindel speed.

This is why you can have the idea the spindle is not turning. There are guys who grip by hand the "standing" spindle. With dramatic effects.

Normally Leds are used with DC voltage and current. If you buy lamps for the main connection you can have all today . Very poor lamps with single diode transfer from AC to DC this cause a frequency of 25 hz. The better ones have a full rectifier with a DC/DC step down converter with 50 to 100 khz.

And from the point of lifetime there are good ones and very poor ones. I returned to the dealer from one serie of lamps the half of the ordered pieces. I openend a few for my own interest and tinkering and found that the led in serie connected die . The others i used for lamps for my 5 inch locomotive.

Werner

[larry phelan 1Participant @larryphelan1]

I was told never to use fluorescent lights anywhere near machines with revolving parts, since they could make it look as if the part was still.

Not a great idea if the chuck is going at a rate of knots !

[SteviegtrParticipant @steviegtr]

I think it is in multiples of 50. Replicating the 50Hz /cycles per second. Strange LED. I have an inverter on the lathe. I have my Dab radio on a shelf just above it. Also an LED worklight. The radio is unaffected by the unfiltered inverter, however sometimes the worklight blanks out the radio reception. Not always, just went it feels like it.

Steve.

[Martin WParticipant @martinw]

I believe it is illegal to fit LED bulbs into a road vehicle that has main and/or dip lamps that were originally designed for for the tungsten halogen style of light. It is probably related to the fact that the LED structure does not have the same/similar physical location and that this then distorts the beam pattern which could be a hazard to oncoming vehicles especially in inclement weather.

Martin

PS

Here is an article that partially covers the law.

(Edit to add above info)

Edited By Martin W on 29/06/2020 00:55:19

[SteviegtrParticipant @steviegtr]

Posted by Martin W on 29/06/2020 00:46:53:

I believe it is illegal to fit LED bulbs into a road vehicle that has main and/or dip lamps that were originally designed for for the tungsten halogen style of light. It is probably related to the fact that the LED structure does not have the same/similar physical location and that this then distorts the beam pattern which could be a hazard to oncoming vehicles especially in inclement weather.

Martin

PS

Here is an article that partially covers the law.

(Edit to add above info)

Edited By Martin W on 29/06/2020 00:55:19

I did look into this before fitting the Philips extreme Led lights. These were very expensive lights & conform with current regs. From memory i paid £132 for them. The problem you raise is that the light defracts & causes glare at the edges of the refractor element. The Philips LED car headlights. Are perfect. I have over the years, spent many hours working on Xenon & LED lights on motorcycles / cars & vans. Most of which were not good for oncoming drivers.

These are great & MOT friendly as my tester who has failed many a vehicle of mine due to this problem has remarked. The beam cutoff point is very good. If you know anything about headlight patterns. You will know how the beam has a cut off & then an angle to match the UK right hand drive code etc. These match. So far i have had them in the Vivaro Sportif for over 2 years without any problems. The light is brilliant. Better than my F-type, which has Bi-Xenon. My motorcycle Multistrada has full LED lights throughout & even turns when cornering. It is a new era.

A snipit . LED lights were illegal in the UK. Suddenly all the new Arriva busses had LED lights. Alla they were no longer illegal.

Steve. My van.

[Robert Atkinson 2Participant @robertatkinson2]

Those Philips LED replacements arre NOT road legal,
The advert you linked to clearly shows the package with a cross through ECE R37 and a "not for use on public roads" warning. The listing also says they are not approved.
There are two interelated reasons for this, technical and apprpval. Technically, as you said, LEDs have competely different optical charatristics to a halogen filament. They are typiclly much larger area and each "chip" has at most a 170 degree emission cone, not the 360 sphere of a filament. The headlights optics are designed for halogen filaments not an LED. You can make a LED replacement that will produce an acceptable beam pattern for a particular lamp design, but it will not work in all lights. The Philips LEDs are probably very good and make an MOT passing beam in your car, but note the MOT just checks for gross alignment errors, not compliance with the full approval requirements.
That takes us to the regulatory part. All mandatory exterior lights on a car (except the reversing light) have to be E marked to show they meet the regulatory requirements. This includes the replaceable "bulbs" which have to meet exact specifications. There is NO specification for LED replacements. So even if you do build the perfect LED replacement the regulatons don't allow )it. Note that none of the cars with LED exerior lights have replacable "bulbs". The whole light is approved and you have to change the whole thing if it goes wrong (you can have up to 30% of individual leds fail before it's an MOT fail). You can get LED replacement sealled beam units as the are a complete lamp.

So basically your car is no longer road leagal. Did you tell your insurance company? If you have an accident they could refuse to pay out (they have to pay the 3rd party claim, but can recover it from you) if they notice. Even worse is if the other driver says you dazzled them.

Robert G8RPI.

Edited By Robert Atkinson 2 on 29/06/2020 06:36:31

[Robert Atkinson 2Participant @robertatkinson2]

Going back on topic, I like others, would nor recommend using a stroboscope to "freeze" the lathe or workpiece.
On inadverent strobing, It is impossible to make generic statements about LED lights as there are too many variables in the electronics that drive them. If they are driven from DC with just a series resistor or analoge constant current source they are fine, but this is now uncommon as it is not efficent. running a lower powered 12V AC/DC MR16 lamps run from a prroper 12V DC supply (NOT a LED power supply unless you are sure it's smoothed DC output), you will probably avoid stroboscopic effects but you might get one that has electronic control rather thn simple resistors.

Robert G8RPI.

[Kiwi BlokeParticipant @kiwibloke62605]

I have set up a strobe to look at a spinning lathe because I'm a curious person (in all senses…). It requires a conscious effort of will not to stick something into the spinning bits 'just to see'. However, I'm willful (again, in all senses).

I assume the strobe frequency was stable, but could not test it properly. It passed some half-arsed tests I subjected it to. What surprised me was the Super 7's spindle could be seen apparently rotating back and forth a little, at a frequency of perhaps a couple of Hz. So there appeared to be a 'torsional vibration'. Was it real? Due to elasticity of the drive belts? Was mains frequency fluctuations to blame? Does anyone care? But it was a pretty experiment…

There are some very pretty videos of Paul Horn micro boring bars in operation, where one side of the work-piece has been cut away, so one can see the inside from the outside (makes sense?) The frame rate, or strobe illumination has been synchronised to the spindle, so it appears as if the tool is magically removing metal. Fascinating!

[Michael GilliganParticipant @michaelgilligan61133]

The control of LED brightness by fast switching [Pulse Width Modulation] is widespread, and very effective.

This application note provides a good overview : **LINK**

https://www.maximintegrated.com/en/design/technical-documents/app-notes/4/4316.html

The perceived brightness of an LED can be increased by rapidly pulsing it at a higher peak voltage than its maximum DC rating, and it can also be dimmed by reducing the mark/space ratio.

The visual effectiveness of this approach depends upon ‘flicker fusion’ and the strobing can sometimes be seen on vehicle rear lights, and on ‘Pelican Crossing’ displays.

There was a burst of enthusiasm for the use of such controllers on microscopes, but; despite the many advantages, there is a serious problem when they are used with some cameras … ‘banding’ can be produced when the scan frequency and the controller frequency interact.

MichaelG.

[Author]

Posts