Pages: [1]   Go Down
Author Topic: Red laser and IR Receivers Yes/No?  (Read 728 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Full Member
***
Karma: 0
Posts: 132
http://roverduino.blogspot.com/ http://uhebeuav.co.za
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Guys simple question.

If i shine a red laser beam into a normal 2 leg IR receiver will i be able to detect n HIGH or n LOW? i know about all the wave lenghts and and and but i don not want to modulate or transmit data just 1/0 detection

any idea?
« Last Edit: November 12, 2013, 06:38:10 am by Rustie0125 » Logged

He who does not try ,does not fail ,does not learn not to fail again http://powerduino.blogspot.com/

Offline Offline
Faraday Member
**
Karma: 30
Posts: 2501
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

yeah why not, you it depends largely on distance.. if it's a weak signal you could use a transistor to switch a logic high for you.

Logged

Offline Offline
Full Member
***
Karma: 0
Posts: 132
http://roverduino.blogspot.com/ http://uhebeuav.co.za
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

I want to use a 5mw laser and max distance will maybe be 20 meters
Logged

He who does not try ,does not fail ,does not learn not to fail again http://powerduino.blogspot.com/

Oregon, USA
Offline Offline
Edison Member
*
Karma: 69
Posts: 2388
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

You will have to test it and see. IR LEDs and photodiodes are rather wavelength sensitive and some don't react to visible light at all. They are also usually covered with plastic that absorbs visible light. Photodiodes designed for the purpose are sensitive to a much wider range of wavelengths.

You can use a red LED to detect red laser light but they respond to light that is somewhat "bluer" than their emission. The following graph shows what I mean (taken from a publication by Forrest Mims):

Edit: on this graph, a red laser (around 630-650 nm emission) will be far to the left


* LED_response.png (129.11 KB, 400x362 - viewed 21 times.)
« Last Edit: November 12, 2013, 11:09:40 am by jremington » Logged

"It seems to run on some form of electricity"

Lacey, Washington, USA
Offline Offline
Faraday Member
**
Karma: 162
Posts: 2502
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

What is a "2 leg IR receiver"? Do you mean a photodiode? Even from IR, that will be a very weak signal.

Didn't we just discuss exactly this question a few weeks ago?
Logged

Steve Greenfield AE7HD
CET Consumer Electronics and Computer
Please don't read your attitudes into my messages

Idaho, US
Offline Offline
Edison Member
*
Karma: 21
Posts: 1026
Special User
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

What is a "2 leg IR receiver"? Do you mean a photodiode? Even from IR, that will be a very weak signal.

I use this circuit:

http://www.fiz-ix.com/2013/04/ir-photodiode-circuit-schematic/

With analogRead(), it can detect IR from an LED reflected off my hand at ~8 inches. It does receive a bit of spurious noise though (1M pullup is pretty weak, and using a stronger pullup drastically reduces sensitivity), which I filter in software (wait for 10 unbroken 'hits') to get a synthesized HIGH or LOW.

If you aimed a 5mw laser right at a photodiode, that should be some pretty intense light even at 20m so even if red is a bit outside the IR range, I'd imagine the photodiode would probably pick it up. You'll have to tweak the analogRead() threshold of course and possibly even the pullup resistor value a little.
Logged

Lacey, Washington, USA
Offline Offline
Faraday Member
**
Karma: 162
Posts: 2502
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Only way to know for sure, is to try it.
Logged

Steve Greenfield AE7HD
CET Consumer Electronics and Computer
Please don't read your attitudes into my messages

Idaho, US
Offline Offline
Edison Member
*
Karma: 21
Posts: 1026
Special User
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Only way to know for sure, is to try it.
Definitely. I think it has a chance but make no promises. smiley-wink
Logged

Lacey, Washington, USA
Offline Offline
Faraday Member
**
Karma: 162
Posts: 2502
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Wouldn't this be simpler with an IR LED focused down, with the red LASER as a visible indication of where it is aimed? Or use a visible photodiode or phototransistor, with a deep red plastic cover over it?
Logged

Steve Greenfield AE7HD
CET Consumer Electronics and Computer
Please don't read your attitudes into my messages

Texas, land of the free, home of the stupid
Offline Offline
Sr. Member
****
Karma: 5
Posts: 268
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Use a DPSS green LASER module instaed.  Green is more visible and Green DPSS uses an I.R. pump diode with A LOT of bleed through of the I.R.

Really, Polymorph's I.R. LED suggestion is a better idea.  Forget the red LASER.
Logged

Dubuque, Iowa, USA
Offline Offline
Faraday Member
**
Karma: 49
Posts: 2544
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Only way to know for sure, is to try it.
Definitely. I think it has a chance but make no promises. smiley-wink
I'll make a promise it'll work (with red).

The intensity of a laser is much greater than any IR LED so when you're looking at the spectral sensitivity graph even the slightest bit of sensitivity will be enough.
Logged

0
Offline Offline
Shannon Member
****
Karma: 215
Posts: 12516
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

If the IR photodiode has a clear lens it will see red photons and response to them as they
are of a higher energy.  In general the shorter the wavelength the higher the energy so
blue photons trigger green or red LEDs as photodiodes, but red photos may do nothing
at all to a blue LED used as a photodiode.  All to do with quantum mechanics and
semiconductor band-gaps.

With a blackened lens most of the visible is filtered out so it all depends how much gets
through (which depends on the dye used and the emission spectrum of the laser).  IR
photodiodes for consumer equipment tend to have black filters so they are not blinded
by sunlight or nearby lamps.
Logged

[ I won't respond to messages, use the forum please ]

0
Offline Offline
Tesla Member
***
Karma: 145
Posts: 9696
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

In an almost identical discussion I suggested one might carefully sand down the lens/filter to let more visible light in.
Logged

Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   smiley-cool

Pages: [1]   Go Up
Jump to: