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Stroboscopic effect

Lathe lighting

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Robert Atkinson 229/06/2020 06:26:01
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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 229/06/2020 06:50:20
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698 forum posts
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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 Bloke29/06/2020 07:29:02
443 forum posts
1 photos

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 Gilligan29/06/2020 08:04:49
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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.

JA29/06/2020 08:21:27
936 forum posts
51 photos

What is the lowest speed that the stroboscopic effect will freeze the motion of a spinning four jaw chuck? In the UK I think it is 375 rpm but I could be wrong.

I have just run my lathe fitted with a four jaw chuck through this speed (slowly changing the speed) and did not see any stroboscopic effect, at all. This was done, first, with only the general workshop lights on (two old fashioned fluorescent tubes) and then with only the lathe light on (cheap domestic LED tube). There was a low level of day light present.

JA

Edited By JA on 29/06/2020 08:22:58

Michael Gilligan29/06/2020 08:59:45
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Posted by JA on 29/06/2020 08:21:27:

What is the lowest speed that the stroboscopic effect will freeze the motion of a spinning four jaw chuck? In the UK I think it is 375 rpm but I could be wrong.

[…]

.

Sorry but there is no easy answer to that [What is the lowest speed?], JA
... It will vary with the individual observer and with the ambient lighting conditions.

The speeds at which ‘freezing’ could take place are easy to calculate ... but the lowest speed at which the effect will be seen is quite a different matter.

MichaelG.

.

Here is an excellent video explanation of the basics: https://youtu.be/KPrSPqfVJhA

Edited By Michael Gilligan on 29/06/2020 09:10:48

Robert Atkinson 229/06/2020 10:58:59
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698 forum posts
16 photos

When I designed LED lighting for microscopes, I Used PWM control because of the efficency, but then filtered it to produce DC through the LED. Basically a switchmode current source with optical and current feedback. It was for quanttive fluoresence so hd to e controlled intensity. I've also used white LEDs as strobes, thay turn off slot faster than a conventional xenon flash lamp.

Robert G8RPI

Michael Gilligan29/06/2020 11:03:30
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15869 forum posts
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This arduino project may be of interest to tinkerers: **LINK**

https://youtu.be/bvwflpb2uj0

MichaelG.

Michael Gilligan29/06/2020 11:06:43
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15869 forum posts
693 photos
Posted by Robert Atkinson 2 on 29/06/2020 10:58:59:

When I designed LED lighting for microscopes, I Used PWM control because of the efficency, but then filtered it to produce DC through the LED. Basically a switchmode current source with optical and current feedback.

.

Good approach, Robert yes

... but I’m sure you don’t need me to tell you that.

MichaelG.

Neil Wyatt29/06/2020 12:25:38
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Posted by Steviegtr on 29/06/2020 02:17:08:
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.

20181117_203534.jpg

20181015_150443.jpg

Hi Steve, did you see what it says on eth seller's page:

PLEASE NOTE: These headlight bulbs do not have ECE approval, and as such their usage is currently not approved for use on public roads: their usage is limited to ‘off-road’ applications. In addition, their installation may trigger a bulb error message to appear on the vehicle's on-board computer system / dashboard. This is a harmless side-effect and may be removed by installing a Philips CANbus Control Unit.

Robert Atkinson 229/06/2020 12:40:15
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698 forum posts
16 photos
Posted by Michael Gilligan on 29/06/2020 11:06:43:
Posted by Robert Atkinson 2 on 29/06/2020 10:58:59:

When I designed LED lighting for microscopes, I Used PWM control because of the efficency, but then filtered it to produce DC through the LED. Basically a switchmode current source with optical and current feedback.

.

Good approach, Robert yes

... but I’m sure you don’t need me to tell you that.

MichaelG.

Thanks Michael,

It was part of this patent
https://patents.justia.com/patent/6878949

But we kept some information back

Robert G8RPI.

C J29/06/2020 23:00:28
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111 forum posts
85 photos

To return to my original post, I successfully cut the custom recess in the soft jaws without any lighting jiggery pokery, after I remembered my lathe has a DRO!? and once I had the diameter set I didn't need to look at the chuck after all blush

 

And my final take on the effect is it might have also been alleviated if I had stuck a card mask on the jaws, so similar to the masking off used in an operating theatre, I could only see and focus on the area I was working on?

 

Edited By C J on 29/06/2020 23:03:51

Neil Lickfold30/06/2020 11:54:07
621 forum posts
102 photos

I once did a job where we used a strobe light to freeze the work piece so to speak so we could more easily see the detail being turned. It worked a treat. But had it only turned on for the duration of that part of the work piece. We latter did some fun things like looking at the way the swarf was coming off the boring bar etc and the strobe was adjusted to be able to see these sort of things. This was back in 1990.

andrew lyner01/07/2020 22:04:24
178 forum posts
2 photos

Mains powered LEDs all (all the ones I've seen, anyway) flicker because the there's no crashing need for a really smooth DC supply and LEDs have no 'memory'. A thin stream of water from the kitchen tap breaks up into apparent drops. But the problem in multi-user workshops was that the background noise made it impossible to know if your machine was running or not. Working on your own is a lot safer in that respect.

If you really want good DC then make up your own lighting circuit in the workshop with a float charged 12V car battery. That will give you a good DC. Never found any problems on my boat. (Otoh, no lathe or bench drill on board)

I remember the lathe in our lab used to have a 24V transformer and a low voltage filament lamp. The flicker was much less detectable due to the greater mass of the filament.

old mart02/07/2020 14:26:09
1824 forum posts
148 photos

Back on topic, my 6 foot flourescent tube in the ceiling of the garage failed the other day, most likely the starter because the ends of the tube were looking good. Nevertheless, I bought a LED replacement which also came with the proper starter (which just says fuse on it). It works ok and I thought I would see if the lathe chuck would strobe. The lathe is a little Warco 7 X 12 with two gears and variable speed to 2500rpm. I had the four jaw chuck on and despite trying all available speeds, I couldn't get it to strobe.

Michael Kerton05/07/2020 09:16:23
3 forum posts

Hi,

Modern fluorescent fittings with high frequency instant start control gear usually operate at about 30kHZ so are well suited for illuminating over lathes. And, now most people consider LED to be the new kid on the block, old style fluorescents are really cheap. Look for fittings that have T5 lamps (thats the skinny lamps). Also, reputable manufacturers claim up to 50,000 hours lamp life. And new style fluorescents are really efficient. As mentioned previously in this post, LEDs are not necessarily robust. Heat is the main killer and quite often the difference between a high end LED fitting and a cheaper one is heat management.

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