Focused beam of photons for LED ?

[petemoore]

  Any suggestions that would better a 'Lazer pointer' at making an LDR to approach it's low resistance at say 15' distance ?
  Or what color lazer pointer would best cause a response in an LDR ?
 

[composition4]

Most LDRs are CdS, which responds best to around 500 - 550nm wavelength light, according to a lot of datasheets.

Which is pretty much green - luckily you can get green laser pointers pretty easily.  Why do you need to trigger an LDR from such a long distance?  Seems that if you didn't line the laser up properly, it wouldn't trigger and they are generally by nature quite focused.  You can get different lenses to disperse the light though...

Jonathan

[Quackzed]

or maybee a layer of soft diffusion over the ldr? layer of clear matte! build a better mouse, er...LIGHT trap! less reflection more absorption.

[Hides-His-Eyes]

You'd have a bitch of a time keeping it lined up even if it did work. Fifteen feet?

[birt]

i've done this for a theater production. a shower had to run for 3 seconds when something crossed the light beam. problem was that after several hours the laser pointer started to dim dramatically (i had it connected to a nokia 3.7V phone charger) i haven't checked what the problem was exactly because it happened at the last couple of performances.

[petemoore]

Which is pretty much green - luckily you can get green laser pointers pretty easily.  Why do you need to trigger an LDR from such a long distance?  Seems that if you didn't line the laser up properly, it wouldn't trigger and they are generally by nature quite focused.  You can get different lenses to disperse the light though...
  Green it is then, easily gotten is a priority.
  10' might even do it, I put 15' just to be difficult, and because that seems like a good, handy #.
  I'm trying to figure out what it takes for me to be able to fairly easily control volume ''remotely''. Often enough I have applications for this particular 'feature' and tire of having to rise constantly to adjust the volume, for instance during programming which is 2x volume, 2x compression, 2x treble enhanced, .00002% 'information, such as a commercial 'break'.
  Another option I've considered is a 2-way motor driving a reduction gear, in a box so that a rubber band can be used to drive the volume control.
  @ <6' I can mechanically control using a twist stick [you guessed it, 6' long, but with a fitting made for the VCKnob fitting] for a potted volume of rotational or slide type, even 'stepped switch' type volume responds to the twist stick at a safe distance for viewing TV.
  Powering the Laser doesn't pose any particular challenge, a flashlight bulb lens could be used to make a larger target.
  If it even works mostly [ie might only have to go like most the way down, which's been pretty easy to get considering the dark R of LDR's], and the amp can accomodate the boost, that'd do the trick, and a trick I could replicate fairly cheaply/easily to get that darn volume control where I need it without wires back and forth across the floor.
  Since the general usage will be under low light, I can probably ''priximity-al-ize'' the light/no light situations to make a VC pretty easy that does enough to satisfy the features I want.
  I've been working with volume controls, and although it may be considered good excersize, it doesn't actually get the heart rate up by much, and it's just a hassle to have to do.
  I'm thinking 1meg to ground'll let most of the signal through [easy to get dark enough for that I think], and 5k'll be a big drop in volume...about right, cheap and fun to try at least.

[R.G.]

Have you thought about using some of the infrared remote control setups? There are chipsets and sender/receiver modules. I think there are RF remotes available as tinkerer's sets too. I used an RF set long a go, about $20 for a sender/receiver set, and it ... just worked... when I tried it.

My aim is terrible. I could never hit something the size of an LDR from 15 feet without some serious aiming.

[R.G.]

I did a search on IR remote controls. These guys have kits and chips for both IR and RF remotes.
http://www.rentron.com/PicBasic/RemoteControl.htm

[R.G.]

Help me, I can't stop~! 
Here's a $8 chip that decodes a stock Sony remote control into momentary switch closures.

http://www.rentron.com/remote_control/IR-D15A.htm


Rats. Now I gotta go update all that remote stuff I was doing. I guess the remote controlled footswitch setup needs a wireless link to it! 

[frank_p]

OHH ! An infrared controller controlled with your brain ?  That would be awesome. 

http://openeeg.sourceforge.net/doc/hw/

[petemoore]

  I didn't know why for sure at the time, but had a strong inkling I was going to be happy I asked this time ! 

[Quackzed]

a regular remote control to switch effects?!? thats very interesting!

Help me, I can't stop~! 
Here's a $8 chip that decodes a stock Sony remote control into momentary switch closures.

Go R.G. go !!! 

[Gus]

Will there be other people around when you are using the laser?   If so you might not want to use a laser because of liability issues from possible eye damage.

[petemoore]

  Good point Gus, and yup, people around the TV/Audio.
  I'm not sure what the cutting/burning power of a laser pointer is, probably enough to be concerned with ''no eye damage''.
 

[Gus]

http://web.princeton.edu/sites/ehs/LabPage/laserpointersafety.htm
http://www.scientificamerican.com/article.cfm?id=can-a-pocket-laser-damage
http://en.wikipedia.org/wiki/Laser_pointer
http://en.wikipedia.org/wiki/Laser_safety