Reply by nuny...@bid.nes March 28, 20162016-03-28
On Sunday, March 27, 2016 at 5:55:22 PM UTC-7, Bob Engelhardt wrote:
> On 3/25/2016 9:39 PM, Cursitor Doom wrote: > > On Fri, 25 Mar 2016 20:46:27 -0400, Bob Engelhardt wrote: > > > >> eBay also has laser "collimating/focusing" lens. How would these be > >> used? > > > > Some of these diodes *need* such a lens, because their raw output is > > ridiculously fanned out, ... > > Some of these products are the raw diodes, which diverge a LOT. But > others are described as "dot" diodes, implying that they have a > collimating lens. And they have a barrel shape that also implies a lens. > > Assuming that they are collimated, how good could it be for these > prices? That's a real question. > > Is it likely that the pieces of a given lot would have the same > divergence? I.e., could one do better than average by picking and > choosing from a lot of 10?
I was wondering the same thing (I also noticed the "dot laser" qualifier)- suppose they're assembly-line rejects and their "dot" is more of an "oval"? No brand name, manufacturer, or UPC available... Mark L. Fergerson
Reply by March 26, 20162016-03-26
The photo detectors in networking gears should be much faster.  We have a bunch of 4 Gb/s fiber channel cards to dismental/experiment with.  I think they can do at least 1 GHz.
Reply by TTman March 26, 20162016-03-26
On 25/03/2016 20:21, Chris wrote:
> Hi all, > > The Chinese are knocking out lasers like these at ridiculously cheap > prices currenty: > > http://tinyurl.com/z59lk8s > > And I've seen others *even* cheaper than that including postage. > > There are a good many applications for these parts that spring to mind, > but the ones I'm thinking about require some sort of sensor capable of > detecting if the beam is broken. I'm not sure what would fit the bill for > this purpose. Light dependent resistors, even if they work well at this > single wavelength (typically 650nm IIRC) are probably too sluggish to > react and useless for all but the most elementary of applications. I'd > like to make something up to measure the RPM of rotating machinery and > need something that will provide a speedier and better-defined response. > Any ideas for a suitable component? >
I've used a standard Sharp I/R detector and modulate the laser at 38KHz... --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com
Reply by nuny...@bid.nes March 26, 20162016-03-26
On Friday, March 25, 2016 at 1:24:48 PM UTC-7, Chris wrote:
> Hi all, > > The Chinese are knocking out lasers like these at ridiculously cheap > prices currenty: > > http://tinyurl.com/z59lk8s > > And I've seen others *even* cheaper than that including postage. > > There are a good many applications for these parts that spring to mind, > but the ones I'm thinking about require some sort of sensor capable of > detecting if the beam is broken. I'm not sure what would fit the bill for > this purpose. Light dependent resistors, even if they work well at this > single wavelength (typically 650nm IIRC) are probably too sluggish to > react and useless for all but the most elementary of applications. I'd > like to make something up to measure the RPM of rotating machinery and > need something that will provide a speedier and better-defined response. > Any ideas for a suitable component?
How much money/time do you plan on investing? http://www.checkline.com/tachometers/?referrer=adwords&gclid=CKWKp-C23csCFQdqfgod6cUBnQ (Not Affiliated) Mark L. Fergerson
Reply by John S March 25, 20162016-03-25
On 3/25/2016 5:27 PM, Ian Field wrote:
> > > "Chris" <cbx@noreply.com> wrote in message > news:nd46kb$9ll$1@dont-email.me... >> Hi all, >> >> The Chinese are knocking out lasers like these at ridiculously cheap >> prices currenty: >> >> http://tinyurl.com/z59lk8s >> >> And I've seen others *even* cheaper than that including postage. >> >> There are a good many applications for these parts that spring to mind, >> but the ones I'm thinking about require some sort of sensor capable of >> detecting if the beam is broken. I'm not sure what would fit the bill for >> this purpose. Light dependent resistors, even if they work well at this >> single wavelength (typically 650nm IIRC) are probably too sluggish to >> react > > LDRs are pretty slow, and the cadmium in them is too toxic to sit well > with RoHS, some suppliers have dropped them altogether - I ordered a > couple of packs from China while I still could. > > Photo diodes suggested by others are probably best, they're certainly > fast enough. Photo transistors are more sensitive, but not as fast as PDs.
Available from Digikey.
Reply by John S March 25, 20162016-03-25
On 3/25/2016 8:14 PM, Andy K wrote:
> On Friday, March 25, 2016 at 4:36:59 PM UTC-5, John Larkin wrote: >> On Fri, 25 Mar 2016 20:21:31 -0000 (UTC), Chris <cbx@noreply.com> >> wrote: >> >>> Hi all, >>> >>> The Chinese are knocking out lasers like these at ridiculously cheap >>> prices currenty: >>> >>> http://tinyurl.com/z59lk8s >>> >>> And I've seen others *even* cheaper than that including postage. >>> >>> There are a good many applications for these parts that spring to mind, >>> but the ones I'm thinking about require some sort of sensor capable of >>> detecting if the beam is broken. I'm not sure what would fit the bill for >>> this purpose. Light dependent resistors, even if they work well at this >>> single wavelength (typically 650nm IIRC) are probably too sluggish to >>> react and useless for all but the most elementary of applications. I'd >>> like to make something up to measure the RPM of rotating machinery and >>> need something that will provide a speedier and better-defined response. >>> Any ideas for a suitable component? >> >> >> Overpriced! >> >> http://tinyurl.com/zu6bfuv >> >> >> Photodiodes: Osram SFH2xx. >> >> >> >> >> -- >> >> John Larkin Highland Technology, Inc >> picosecond timing precision measurement >> >> jlarkin att highlandtechnology dott com >> http://www.highlandtechnology.com > > At 22 cents each, I wonder how they would last ? > > Andy
They claim at least 1000 hours. Count on it.
Reply by Cursitor Doom March 25, 20162016-03-25
On Fri, 25 Mar 2016 20:46:27 -0400, Bob Engelhardt wrote:

> eBay also has laser "collimating/focusing" lens. How would these be > used?
Some of these diodes *need* such a lens, because their raw output is ridiculously fanned out, so some form of correction is required. I'm not quite sure of the technical term for it, but it needs to be a lens (or for best results 3 lenses in combination with each other) which focus primarily in one plane.
Reply by Andy K March 25, 20162016-03-25
On Friday, March 25, 2016 at 4:36:59 PM UTC-5, John Larkin wrote:
> On Fri, 25 Mar 2016 20:21:31 -0000 (UTC), Chris <cbx@noreply.com> > wrote: > > >Hi all, > > > >The Chinese are knocking out lasers like these at ridiculously cheap > >prices currenty: > > > >http://tinyurl.com/z59lk8s > > > >And I've seen others *even* cheaper than that including postage. > > > >There are a good many applications for these parts that spring to mind, > >but the ones I'm thinking about require some sort of sensor capable of > >detecting if the beam is broken. I'm not sure what would fit the bill for > >this purpose. Light dependent resistors, even if they work well at this > >single wavelength (typically 650nm IIRC) are probably too sluggish to > >react and useless for all but the most elementary of applications. I'd > >like to make something up to measure the RPM of rotating machinery and > >need something that will provide a speedier and better-defined response. > >Any ideas for a suitable component? > > > Overpriced! > > http://tinyurl.com/zu6bfuv > > > Photodiodes: Osram SFH2xx. > > > > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
At 22 cents each, I wonder how they would last ? Andy
Reply by Bob Engelhardt March 25, 20162016-03-25
eBay also has laser "collimating/focusing" lens.  How would these be used?
Reply by dcas...@krl.org March 25, 20162016-03-25
On Friday, March 25, 2016 at 4:24:48 PM UTC-4, Chris wrote:
> Hi all, >
I'd
> like to make something up to measure the RPM of rotating machinery and > need something that will provide a speedier and better-defined response. > Any ideas for a suitable component?
For just one................. eBay item number: 252230277757 Dan