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Red laser detector

Started by Chris March 25, 2016
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.
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
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
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.
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