Lathe strobe

[Sshire]

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

 

[Ed T]

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.

 

[Sshire]

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.

 

[stew]

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

 

[Jasonb]

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

 

[MuellerNick]

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

 

[Herbiev]

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

 

[MuellerNick]

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

 

[Ed T]

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.

 

[Sshire]

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

 

[MuellerNick]

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

 

[MuellerNick]

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

 

[Sshire]

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

 

[MuellerNick]

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

Nick

 

[tel]

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

 

[Rocketcaver]

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:

 

[MuellerNick]

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

 

[Rocketcaver]

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.

 

[Sshire]

Has something to do with working around inclusions in burls.

 

[tel]

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.