DPRG
DPRG List  



DPRG: IR stuff

Subject: DPRG: IR stuff
From: Sean Jones shain at noln.com
Date: Wed Jul 30 02:56:49 CDT 1997

Hello,

Since you have the stuff, a good place to check out is:
http://www.nwlink.com/~kevinro/guide/infrared.html

He has a whole page dedicated to ir detection.

Sean

Clay Timmons wrote:

> > I have bought a Radio Shack Infrared Emitter and Detecor. (two LED
> alike)
> > Does anyone have any simple circuit(the simplest) to test them ?
> >
> > I have also bought a IR Detection module but this one is a 3 pinner
> does
> > anyone have some simple circuit for that  too ? (That is after I
> would
> > make the first one work, ok ?
> >
> > P.S. Or maybo someone knows a WWW address where these circuits would
> be
> > shown ?
> >
> > Later,
> > Cyborg
> >
> >
>
> To test them just breadboard the following two circuits.
> Monitor the ouput voltage while you turn the transmitter on and off.
> If everything is working you should see a big difference in the
> output.
>
> The transmitter is just an LED with the standard current limiting
> resistor.
> Adjust resistor value for supply voltage and desired drive current.
>
>              R           LED
>
>                          | /|
>    V+  --/\/\/\/\/\/\----|< |------------- GND
>                          | \|
>
>
> Receiver is equally simple. The receiver is an NPN phototransistor.
> It may have three leads or two.  In either case only two are needed,
> the collector and emitter.  Add a pullup resistor to the supply
> I use about 10K, with the phototransistor pulling down to ground
> depending on the amount of IR light received.  Output is the
> voltage between the resistor and phototransistor.  The output can
> go directly into a microcontroller digital input (cheesy) or
> to a schmidt trigger or comparator (better) or to a D/A converter
> (best).
>
>             R        Phototransistor
>                     Collector  Emitter
>
>    V+  --/\/\/\/\/\/\----\      /------------ GND
>                           \    /
>                            \  ^
>                           ------
>
>
>
> The IR phototransistors are sensitve to visible light as well.
> The best solution is to enclose them in a light shield like
> opto-couplers and shaft encoders do.  For applications
> where visible light is present an IR filter
> (red plastic found on remote controls) helps limit the visible
> light.  A much better approach to deal with the problem
> of ambient light is to modulate the signal like remote
> controls do with 40Khz pulses.  In that case you can use
> the little IR detection module from Radio Shack and a different
> type of transmitter.
>
> -Clay Timmons   ctimmons at asic.sc.ti.com
>
>
>
>
>

------------------------------

More information about the DPRG mailing list