Stroboscopic effect

[JAParticipant @ja]

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 GilliganParticipant @michaelgilligan61133]

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 2Participant @robertatkinson2]

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 GilliganParticipant @michaelgilligan61133]

This arduino project may be of interest to tinkerers: **LINK**

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

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

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

MichaelG.

[Neil WyattModerator @neilwyatt]

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.

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 2Participant @robertatkinson2]

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

… 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 JParticipant @cj88518]

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

 

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 LickfoldParticipant @neillickfold44316]

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 lynerParticipant @andrewlyner71257]

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 martParticipant @oldmart]

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 KertonParticipant @michaelkerton45997]

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.

[Author]

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