Author Topic: Anybody build Dan Gelbart angled laser centre finder? (Read 88022 times)

DavidA · « **Reply #100 on:** April 19, 2015, 05:28:15 PM »

Norman mentioned 'Centre cam'.

I remember that article, and did download Trethaway's software.

Did anyone here actually build one?

Dave.

BaronJ · « **Reply #101 on:** April 21, 2015, 03:34:35 PM »

Hi Guys,

I just found this on the HMSC web site.
There is a PDF article on there but the interesting bit starts at page 5. I just grabbed an image of the wanted pages.

awemawson · « **Reply #102 on:** April 21, 2015, 03:45:07 PM »

I like the simplicity of using centrifugal force to operate the switch - very neat

Arbalist · « **Reply #103 on:** April 22, 2015, 01:39:39 PM »

It's an innovative slant on the concept but I'm concerned about the safety aspect of one Laser, let alone two working at the same time. I'm also worried that two circles may prove to be distracting rather than helpful. Nice to see folks trying something different though.

PekkaNF · « **Reply #104 on:** April 22, 2015, 02:17:53 PM »

I have worked around and installed low power laser sensors and safety curtains/photocells. This power level is considered fairly safe. Generally laser beam is actually pretty thick and mW level laser has pretty low power density.

This design I would consider pretty safe, there is no good reason to stare into the beam. Reflection from the part is possible, but due to spinning "dwell time" is pretty low and these power levels are most likely don't cause damage on stray exposure.

That said, I consider my sight very important and I would very much use lowest power level that works.

Probably whole lot more damaging to our eyes is welding and UV exposure from leds/displays/TVs and stuff.

Pekka

Arbalist · « **Reply #105 on:** April 22, 2015, 04:19:29 PM »

Good to know Pekka.

I have ordered what is described as a 1mw Laser from Hong Kong. The primary reason for ordering another is that it is smaller than the one I have at present so if suitable it will be easier to mount. Should arrive in a week or two.

PekkaNF · « **Reply #106 on:** April 23, 2015, 02:56:20 AM »

I ordered three "smaller" lasers as well, will take some time to get them. Those are small, but not "focusable", hope they are weaker. I have intention to check which parts I need for collimation, but I got sidetracked with ND filters and polarization if I need to live with this one. Some math involved to collimation lens calculation and some input values are required that not all are available....I will resort to normal lens calculator and approximate, questimate and testimate it.

Which laser you bough? I'm hating the idea of getting too exited and buying too much junk. "Just in case". But this is pretty cheap way to learn more.

Pekka

Arbalist · « **Reply #107 on:** April 23, 2015, 04:33:35 AM »

This one Pekka.

http://www.ebay.co.uk/itm/381148296821?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

PekkaNF · « **Reply #108 on:** April 26, 2015, 04:54:55 AM »

Got one cross-line 5mW laser from mail.

I got some time to play with this cross-line laser.

1) I took the cap/grid lence off and noticed that there is a lense (group?) on threaded holer, that allows "focus" adjustment.

2) Original dot is not extremely clean, about the same than "focusable laser module" that has been linked here.

3) Tried prism to angle the beam and it worked out pretty well. I was expecting some artefact here, but quick look seems to confirm that with a little adjustment laser and prism will compensate oavality of the beam.

Laser inside a grey plastic cable gland
prism from a binoculars (roof prism type, pechan prism used)
ND filter, thanks Vic
Black cardboard.

It looks like it is possible to use prism, but to adjust the beam only with the prism is not optimal. Surface mirror?

Pekka

PekkaNF · « **Reply #109 on:** April 26, 2015, 06:28:27 AM »

Little testin with pinhole.

1) I made a pinhole onto black craft cardboard, smallest pin I had.
2) I placed the pinhole on front of the collimation lense and it produced interference rings as theoriy says, clearly visble when focused on about 200 mm and then viewed at three meters trough frosted glass.
3) Dot density is greatly reduced and dot is pleasingly round, but not exceedingly small at 200 mm, due to interference no doubt. However when projected onto machined metal surface it looks very promising.

My gut feel about this (not very sientifically based) is:

Pinhole can be used to clip the size of the dot, but to be highly effective it needs to be placed carefully, probably near focal point and in this system it means some extra lenses.

Pinhole naturally cuts some intensity, specially when placed into "wrong place" wether this is good or bad depends on situation.

ND filters I got do no seem to reduce quality of the beam.

Pekka

Arbalist · « **Reply #110 on:** April 26, 2015, 04:06:55 PM »

I couldn't see any interference rings with the setup I used. It may be they are still there, just too feint to see? I have another mounting prepared ready to drill when the micro drills I've ordered arrive so we'll have to see what happens with that. I can't see the need for a prism unless for some reason you really want to mount the Laser horizontally? Adding a mount to house a ND filter and a reduced aperture increases the bulk somewhat but it's still small enough to use. The other Laser I've ordered is very much smaller so it will be interesting to see how compact this assembly will be. I'm still favouring a button cell, maybe a CR2032 if it lasts long enough.

PekkaNF · « **Reply #111 on:** April 27, 2015, 05:27:52 AM »

As you see on the bottom picture, interference artefact is not that visible on reflected light at 200 mm distance, but I assume that dot appear bigger because of that. The picture where interference shows is the same beam, but at three metres trough matte glass. When I viewed at laser side the effect was not very clear just a bigger dot (about 2-3 cm). But at the other side the effect is very clear. Last picture shows the interference nicely (Picture is taken at a angle, because head on the picture was just just a big blow of red light, but vhen observed the rings were very consentric and all around the central dot). But the dot was really round, only the interference rings to make it too large.

I'm testing the prism, because I want to slip the indicator at the end of the spindle and there is space only to very thin object. Therefore my preference is to make this flat, but if that is too much trouble or the smaller laser is not small enough, then "Plan B" is to fabricate one that will slip over dedicated ER holder - not as versatile, but plenty of headroom.

I don't know much of the pinholes, but I think that thinner the material you have the better the results are. I could not find my very thin copper foil, but I should have somewhere a little of thin brass shim stock and I was thinking of comparing that with domestic aluminium foil - hole pricked with a needle.

Pekka

Arbalist · « **Reply #112 on:** April 27, 2015, 08:09:02 AM »

Interesting about the foil. I'm wondering about how to make a fixture for centering the hole on the lathe. I have some steel shim stock somewhere that may suffice. I think in one of the videos linked earlier someone was using the edge of razor or craft blades to chop the laser image.

PekkaNF · « **Reply #113 on:** April 27, 2015, 08:25:51 AM »

Quote from: Arbalist on April 27, 2015, 08:09:02 AM

Interesting about the foil. I'm wondering about how to make a fixture for centering the hole on the lathe. I have some steel shim stock somewhere that may suffice. I think in one of the videos linked earlier someone was using the edge of razor or craft blades to chop the laser image.

I linked one video where instructor was using razor blades on magnet. pretty smart really, razor blade edge is pretty sharp and on magnet you have an adjustable iris.

This foil I haven't tried, but I read it somewhere. I noticed that it was easy to prick the hole on black cardboard and then pretty damn hard to align it to the beam. Hmm. Could a copper/brass metal foil be glued on a washer or something that has few mm hole and the pin hole middle of it? Thicker carrier should be easier to align and hole on the carrier should give better visual where about the beam should hit. Pity that local bolt shop does not have setscrews with pinholes on them. I have used some hydraulic orifices that were like that, but the bore was too long for this.

Any small plumbing fibre washer/cap olive fitting?

Pekka

Arbalist · « **Reply #114 on:** April 27, 2015, 09:30:13 AM »

Thinking about it some more you could make a housing for the Laser similar to one I posted earlier. The ND filter slips in the bottom of the housing below the Laser. The aperture could be drilled out somewhat bigger then a piece of foil could be glued on the outside and then drilled with a small hole on the Lathe.

PekkaNF · « **Reply #115 on:** April 27, 2015, 03:10:07 PM »

And the mailman brought small lasers, quick and dirty testing showed that these would simplify mechanics greatly.

Pekka

awemawson · « **Reply #116 on:** April 27, 2015, 03:21:50 PM »

When this thread started I ordered a job lot of 50 of those small ones for a ridiculously small amount on ebay. Did a quick and dirty test with a variable voltage and current psu and was most impressed.

They then went back in the bag and still are sitting on the desk waiting for time to make a mock up

I have to say reading all that's been said people seem to be making this far more complicated than Dan's original simple concept

But what do I know, mine are still in the bag

vtsteam · « **Reply #117 on:** April 27, 2015, 03:35:55 PM »

Andrew, it's the brickwork holding you back. After that's done, then you can start on the planetarium...

awemawson · « **Reply #118 on:** April 27, 2015, 04:44:42 PM »

Quote from: vtsteam on April 27, 2015, 03:35:55 PM

Andrew, it's the brickwork holding you back. After that's done, then you can start on the planetarium...

Steve I have to say the brickwork progress is hugely frustrating at the moment, that and we still haven't finished lambing (only 3 Ewes left to pop but they seem to be hanging it out deliberately and we have several needing bottle feeding)

I'm determined not to get involved deeply in another project until at least the pig sty and lambing is finished

Arbalist · « **Reply #119 on:** April 27, 2015, 05:12:52 PM »

They look like the one I've ordered Pekka.

Arbalist · « **Reply #120 on:** April 29, 2015, 09:33:36 AM »

A few items I ordered have now arrived. I drilled the new housing I'd made for the 12mm module with a .5mm drill bit but the resultant dot size seemed little different from the earlier one with a .75mm aperture. The 6mm laser module arrived and seems less bright than the 5mw laser pointer I have which is fine. The dot is still oval though and the focus has been glued in place so I can't adjust it without risk of breaking the module. I'm sure it will be fine though if I use a small aperture again. Not sure yet if it will benefit from a ND filter. Overall I'm quite impressed with the 6mm unit, inexpensive and very compact. Time to design a prototype.

Andrew Wildman · « **Reply #121 on:** May 02, 2015, 03:13:28 PM »

Here is a laser centre finder that I put together. Most parts were 3d printed.

It looks a bit like a laser guided toilet seat for mice but the strange shape is allow it to be used on a number of different machines with different spindle sizes. The centre finder is fixed to the spindle with magnets and is very stable when running, even on the drill where it looks a bit precarious!

Andrew Wildman · « **Reply #122 on:** May 02, 2015, 03:15:37 PM »

A shot of it in action

sorry about the massive pics, the pics on the last post were a sensible size but for some reason these are much larger

philf · « **Reply #123 on:** May 02, 2015, 03:17:25 PM »

Very nice Andrew.

That's one of the few useful things I've seen made with a 3d printer.

Phil.

PekkaNF · « **Reply #124 on:** May 02, 2015, 04:07:24 PM »

That looks nice.

What kind of results are you getting with that one?

I attented on one 50th birthday party and next day when I was returning from the trip I went on one "El cheapo" shop and tried to find something usefull for a 3V lithim batery holder. No, they had no cell clips, but there was a pagage of three electric candles and six batteries for about 3€. When I got home I cheed them and what a luck. The bottom part is one itegral unit and and it detaches with two philps screw, the bottom is about 34 mm round "lid" that has a battery holder and switch in one ready made unit. battery size is small, but this offers all the parts for further testing and some spares.

Something like this:
http://m.dhgate.com/product/electric-candle-tart-warmer-flameless-led/210849539.html

Battery tab and switch tab are solder tabs, quick to substitute the "candle led" with laser module. Seems to work.

3D printer could make holder easy.

I tried do dig a chunk of aluminium for the spinng part, but maybe a plastic would do.

I'm procrastinating between two fixed angle lasers, switched alternately or one adjustable angle laser....and two different attachmet method. I don't like the magnets. I have idea about coaxial excentrics or wire spring....

Pekka

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Author Topic: Anybody build Dan Gelbart angled laser centre finder? (Read 88022 times)