# Lathe strobe



## Sshire (Nov 26, 2012)

My brother is a Woodturner (can't convince him to stop using that brown stuff)
He wants to have a strobe synced to his lathe (approx 50 - 2000 rpm).
Would an auto timing light work? If so, what to sync it? Hall effect sensor? How would one hook this up?
I'm at a loss with 'lectrical stuff.
Thanks for any suggestions


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## Ed T (Nov 26, 2012)

What does he want the strobe to do? Usually when using a strobe to "stop" fast moving devices so you can see what's going on you simply adjust the strobe frequency 'til the motion is stopped. Some strobes have an accurate enough frequency output that you can tell what speed things are going although it helps to have some idea of what the answer should be since there may be several synchronous frequencies. If he wants to know how fast its turning, there are much simpler ways. I think HF sells a non contact optical tach.


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## Sshire (Nov 26, 2012)

He wants to stop the motion. His lathe is a variable speed with VFD and RPM display, and if he varies the speed, he would like the strobe to stay in sync rather than fiddling with knobs.


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## stew (Nov 27, 2012)

HI,
I would be very careful on fitting any type of Light to a lathe that can create a Strobe effect. Just as an example ( I have never had the experience Myself) Fluro Lights fitted above a Lathe  have been known to cause a Strobe effect which as a result had caused some Serious accidents.
All The Best Stew


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## Jasonb (Nov 27, 2012)

Youdon't want a strobe that needs to be traiggered to flash at the same rpm as the lathe usually by cionnecting to the ignition.

Something like a small lazer tachometer will do I have used one out of curiosity on my lathe, just point at the lathe chuck and the jaws trip the tacho then divide the reading by 3. They can also be tripped by attaching a reflective tape to the spindle, chuck etc which will only trip once per rev so no need to do the maths.

The variable speed lathes use a rotor on the spindle with a read head that gives the reding


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## MuellerNick (Nov 27, 2012)

An auto timing light will not work. They need a high voltage (taken off the HV cable) to trigger.
There are strobes available, that have different means of triggering, but they tend to be way more expensive as they have more features like phase shifting, frequency readout etc.

If you google, you might find schematics for a simple strobe that works with (flash-)LEDs. These would work with low voltage triggering.


Nick


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## Herbiev (Nov 27, 2012)

That is the same tacho I got for about $8.00. It works great. Just put a dab of typists "white ink" or similar on the chuck and get a very accurite reading


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## MuellerNick (Nov 27, 2012)

The OP isn't looking for a tach, he looks for a strobe light that is in sync with the spindle.
At least that's what my reading skills tell me.


Nick


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## Ed T (Nov 27, 2012)

OK if what he wants to do is basically make it look like his lathe and work are not turning when they really are I think it is doable, but fairly spendy. There are stroboscopes (Monarch, Shimpo) with external trigger capability so that the frequency of the flash is synchronous with the external frequency signal Once you get it set up it should track the speed pretty well. I can think of two ways to generate an external trigger signal, but there are probably many others. I'm not an EE so the details will have to be handled by others. The first way is to use an inductive pick up on the power lead to the motor. The power frequency varies with the speed (hence VFD). This frequency signal then goes into a TAMO (then a miracle occurs) box and is converted into a signal that the scope can use as a trigger. There may even be an output on the VFD drive that already does this, but you'd have to look at the specs for the drive to find out. The second way is to use an optical sensor from some rotating part of the spindle and feed that into a slightly different TAMO box to produce the signal for the strobe. I think the second way is simpler and more directly coupled to what you brother wants to see. This kind of strobe is north of $500 and you will need to find someone to make a TAMO box. You might be able to get some tech help from the strobe makers. It wouldn't surprise me if an optical pick off driver might be something that exists. That said, it's a lot of bux. Maybe your brother can learn to blink real fast.


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## Sshire (Nov 27, 2012)

Ed
Thanks for understanding the question and for the excellent answer.
We may have moved from auto-sync to "turn the knob until the spinning stops"
I'll report on what develops.
Stan


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## MuellerNick (Nov 27, 2012)

> We may have moved from auto-sync to "turn the knob until the spinning stops"



You'd regret that move!
The VFD isn't stable at holding RPM. As soon as the spindle gets some load, the RPM will drop a bit and the strobe is out of sync (it never was*)). So your part will look like it slowly rotates.

*)
If you don't take off a trigger impulse from the spindle, the strobe will NEVER be at the same place, your spindle will ALWAYS look like turning in one or the other direction.


Nick


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## MuellerNick (Nov 27, 2012)

Here is a schematic of a LED timing light.
That one still takes off the trigger impulse from the HV line. But the input stage can be converted to work with 12 V (it already does, needs a different sensor).


Nick


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## Sshire (Nov 27, 2012)

Nick
You are talking to an electronics idiot. I was ok when I was 12 and had a ham radio license and everything was tubes. 
I do get the circuit. What would be required for 12v operation?
Thanks again
Stan


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## MuellerNick (Nov 28, 2012)

If you want to use a photoelectric barrier, there are certainly app notes in the data sheet.

Nick


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## tel (Nov 28, 2012)

Sounds like an easy way of losing a hand to me.


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## Rocketcaver (Nov 28, 2012)

This would be a fun problem to solve, but I really don't see why he wants it.  Yeah, it would be pretty cool, but to serve what purpose?  Sounds like an invitation for an accident to me.  
I for one would rather NOT be fooled into thinking a largish chunk of (something potentially harmful) was not rotating at a fairly high rate of speed. :shrug:


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## MuellerNick (Nov 28, 2012)

> I for one would rather NOT be fooled into thinking a largish chunk of (something potentially harmful) was not rotating at a fairly high rate of speed.



You'll still see the part is rotating.
Except you close all doors, close all window blinds, shut off all lights and use the strobe as only light source. And then, you still hear the lathe is running.

I'm not aware, that the timing lights for cars are considered so dangerous as using the same principle with a lathe.


Nick


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## Rocketcaver (Nov 28, 2012)

MuellerNick said:


> You'll still see the part is rotating.
> Except you close all doors, close all window blinds, shut off all lights and use the strobe as only light source. And then, you still hear the lathe is running.



Yes, I was exaggerating obviously.


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## Sshire (Nov 28, 2012)

Has something to do with working around inclusions in burls.


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## tel (Nov 29, 2012)

Perhaps, but I don't wanna be in the same room with it.

Strobing occurs occasionally with lathes lit by fluro strip lighting - we go to great lengths to get rid of it, not do the opposite.


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## Gedeon Spilett (Nov 29, 2012)

What you need is a DC light (i.e. a car headlight with battery to keep things simple and cheap) chopped at the same frequency of the lathe. It can be a mechanical shutter like in a movies projector connected with the lathe spindle.


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## Rocketcaver (Nov 29, 2012)

Ok, I'll chime in here.  
Get a few of those real bright white LED's.  
Fasten a magnet to the lathe chuck, or somewhere else out of the way.
Use a reed switch or hall effect sensor to turn the LED array on when it "sees" the magnet.
This will give you a pulse of bright light on every revolution of the work.  If your LED array is bright enough (you can get some VERY bright LED's these days), you will have your strobe effect.
A regular car headlight does not turn on and off fast enough due to the relatively slow heating and cooling of the bulb filament, but the LED array is essentially instant on and instant off.

Later...

Oops!  I see that MuellerNick has already made basically the same suggestion.  That circuit would be pretty easy to duplicate, and would do exactly what you want.


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## MuellerNick (Nov 29, 2012)

Initially, I thought a reed switch would not be fast enough. But they go up to 300 Hz. That would be 18000 RPM.
So a reed switch is the simples way, together with the LED strobe I linked to.


Nick


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## GailInNM (Nov 29, 2012)

For safety reasons I would like to see this thread die at this time.  As it does not violate any rules I am not locking it.

Our  hobby is dangerous by it's nature.  Any time we do something that makes  it more dangerous should be balanced by additional safety measures and  an examination to make sure that any additional hazard is necessary to  accomplish the task.

Gail in NM


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## MuellerNick (Nov 30, 2012)

That's what you get under professional conditions. Certainly done with a intense flash in a dark room.

[ame="http://www.youtube.com/watch?v=78XYpr2Vnvg"]YouTube[/ame]


Nick


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## skyline1 (Nov 30, 2012)

GailInNM

I agree with you entirely and as for car tacho strobes not being dangerous. They are, for just this reason. There are bold warnings printed on them to this effect.(mine certainly has).

Regards Mark


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## MuellerNick (Nov 30, 2012)

> There are bold warnings printed on them to this effect.(mine certainly has).



My US-made lathe has about 2 square meters of warning stickers on it with blood and body parts splashing around.
But I still can stick my head between the running chuck and bed if I prefer.


Nick


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## skyline1 (Dec 1, 2012)

Hi Nick

Yes quite true, This modern Health and Safety Obsession does go a bit far sometimes. Most manuals for anything the slightest bit technical seem to be 50% safety warnings and 50% operating instructions. And some of them are obvious to the point of being silly Who is likely to immerse their T.V. in water for example but the warning is still there. A strobe device like this that can make a rotating part appear stationary does carry an additional risk though and a very real one.

Regards Mark


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## lampy (Dec 1, 2012)

I'm missing something  What is the benefit of the strobe other than making a cool video to market your cutting tools?


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## ELM6061 (Dec 1, 2012)

lampy said:


> I'm missing something  What is the benefit of the strobe other than making a cool video to market your cutting tools?



Using a metal lathe, you know the dimensions of your raw material and also the dimensions of the material you are going to remove. You then control your sight/cuts using your dial indicators, specially if they are internal cuts.

Using a wood lathe and specially true if your raw material is tree burls or logs, you have no idea of actual dimensions and all your cuts are by freehand and by sight. Using a wood lathe, you have no dial indicators and if you make a cut to deep or the edge of your chisel catches on an edge of your work piece, the consequences can be catastrophic. As shown in the video with an internal cut and with an incursion to the work piece, having a strobe that fires with each revolution can actually be seen as having a safety feature, as it shows you exactly where you are cutting and how much material you have left.

I have seen one made using a reed switch, but sorry have no idea of the wiring diagram. Shouldn't be to hard to make up though.

Eddie


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## lampy (Dec 1, 2012)

Thanks for the explanation. So it is more of a wood lathe application that could also be used on a metal lathe.


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## ELM6061 (Dec 1, 2012)

lampy said:


> Thanks for the explanation. So it is more of a wood lathe application that could also be used on a metal lathe.


I am not an experianced machinist in either application (wood, metal), though I have watched a strobe being used on a wood lathe several times and that was the explanation/reasoning I was given. 
As for this application and the reason this thread was started, yes it is for a wood lathe.


Sshire said:


> My brother is a Woodturner (can't convince him to stop using that brown stuff)
> He wants to have a strobe synced to his lathe (approx 50 - 2000 rpm).
> Would an auto timing light work? If so, what to sync it? Hall effect sensor? How would one hook this up?
> I'm at a loss with 'lectrical stuff.
> Thanks for any suggestions


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## dman (Dec 2, 2012)

i haven't read the whole thread but i fail to see why the automotive timing light is being discouraged. a timing light uses some kind of clamp sensor, there are a few types but my understanding is that they are all designed to measure current not voltage. 

http://en.wikipedia.org/wiki/Clamp_meter

the voltage of the source it's detecting is irrelevant. the energy that the pickup provides is very small and can likely be created with a hall effect sensor, if not directly you can likely step up the signal easily with a transistor and external power source. 

a timing light is cheap enough to cut up and the cheaper ones actually work better, the one with digital displays and timing knobs are never as accurate as the non adjustable ones.. you can either do some research and get a better idea of if it works or just cut the pickup off of one, get a 12v transformer and coble up a sensor and try it out.


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## MuellerNick (Dec 2, 2012)

> a timing light uses some kind of clamp sensor, there are a few types but my understanding is that they are all designed to measure current not voltage.



A timing light uses capacitive coupling. One side of the capacitor is the clamp, the other the HV wire. If you want to get awake (= get an electrical shock), simply touch the wire coming from the clamp. There should be at least something like 400 V. That's the voltage needed to ignite a xenon bulb (that are used in almost all timing lights).


Nick


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## dman (Dec 2, 2012)

MuellerNick said:


> A timing light uses capacitive coupling. One side of the capacitor is the clamp, the other the HV wire. If you want to get awake (= get an electrical shock), simply touch the wire coming from the clamp. There should be at least something like 400 V. That's the voltage needed to ignite a xenon bulb (that are used in almost all timing lights).
> 
> 
> Nick



my timing lights have two wires running to a clamp. if it was capacitive it would only need one and if the voltage drove a xenon bulb directly like that it wouldn't need a 12v source only a grounding point. but my lights do need a 12v source, both positive and negative. 

maybe the lights they use i europe are different. i'm sure that's how it was here in the old days but all the lights i've handled don't appear to work that way.


edit; as it's been mentioned above, after some searching, capacitive timing lights and inductive timing lights both exist. an inductive timing light may serve the purpose. but not a capacitive light without some extra circuitry.


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## MuellerNick (Dec 2, 2012)

> if it was capacitive it would only need one and if the voltage drove a xenon bulb directly



I wrote "ignite". The cheap timing lights take off part of the high voltage and lead that to the ignition contact of the tube. That has nothing to do with the voltage for the bulb that makes the flash. A Xenon tube has 3 contacts, not just two.


Nick


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## dman (Dec 2, 2012)

MuellerNick said:


> I wrote "ignite". The cheap timing lights take off part of the high voltage and lead that to the ignition contact of the tube. That has nothing to do with the voltage for the bulb that makes the flash. A Xenon tube has 3 contacts, not just two.
> 
> 
> Nick



all i can tell you is that my timing light in fact has an inductive pickup. i just pulled apart the clamp and it contains a u shaped core and is wrapped with a coil that drives the light circuitry. capacitors have two plates separated by a dielectric sometimes a cylinder inside a cylinder seperated with a dielectric (the plug wire casing would be the dielectric in this case). inductors have a permeable core wrapped in a coil. believe me many timing lights do not use capacitive coupling. 

i could be wrong but is it some coincidence it says "inductive timing light" down the side? 

and just for S's and g's  i disconnected the cables from the light and started up my car with the clamp on the number 1 cable to measure the voltage and got a mere 3mv AC. i know that's RMS voltage and I'm not measuring a full sine wave so it's not a clear picture of what the peak voltage is so i then stuck my thumb over the leads and felt absolutely nothing. 

I've already admitted there are capacitive lights but I've never seen one for sale in the states. I'm saying that a light with an inductive pickup may work for the purposes of the op. 

if i had a scope i could measure the signal voltage and try to trigger the light without the pickup but i don't have the equipment.


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