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'basic stamp infrared'
1995\07\03@004620 by Mike Brothers

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Dear All,

I am working on a Basic Stamp project that detects IR from a
standard tv remote control.  I tried to use a standard IR
phototransistor but found that I had to place the remote control
within 1/4" for it to work.  I then tried using a transistor to amplify
the circuit.  I coupled the collectors of the phototransistor and
transistor, and connected the emitter of the phototransistor to the
base of the transistor.  In a darkened room, the circuit worked great.
But in normal room light, the circuit acted as if it was continuously
detecting IR.  I tried using an IR filter lens from a remote control
to shield the phototransistor, but it did not seem to help.

Question:  How do I reduce the sensitivity of the IR phototransistor
to normal light?  Should I scrap this idea, and use the GP1U52X IR
receiver module mentioned in Basic Stamp application note #11?

Any help you can give me would be greatly appreciated!

Mike Brothers
spam_OUTelectronTakeThisOuTspamwln.com

1995\07\03@022940 by Andrew Warren

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Mike Brothers <.....electronKILLspamspam@spam@WLN.COM> wrote:

>I am working on a Basic Stamp project that detects IR from a
>standard tv remote control.  I tried to use a standard IR
>phototransistor but found that I had to place the remote control
>within 1/4" for it to work.
> ....
>Question:  How do I reduce the sensitivity of the IR phototransistor
>to normal light?  Should I scrap this idea, and use the GP1U52X IR
>receiver module[?]

Mike:

IR remote controls modulate their signal on a 40 KHz (or so) carrier.
Your receiver must include a highpass filter to block frequencies below
this.  The receiver modules are probably your best bet; they include
the filter, amplifiers, etc.

-Andy

--
Andrew Warren - fastfwdspamKILLspamix.netcom.com
Fast Forward Engineering, Vista, California

1995\07\03@035912 by Lotty

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Mike wrote:

>> I am working on a Basic Stamp project that detects IR from a
>> standard tv remote control.  I tried to use a standard IR
>> phototransistor but found that I had to place the remote control
>> within 1/4" for it to work. ....

Why not using a special IR-receiver device like SH205(?)?
Thease things work quite good (very sensitive) and aren't expensive.
Inside there is an optical IR-filter, a 44kHz filter, impulseformer
etc. They are supplied over a 100 Ohm resistor and need an electrolytic
cap. At the out-pin delivers a recangular signal like that:

IR _____|_|_|_|_______
        _____
OUT ____|     |_______


              _____
             |  _  |
       100R  | |_| |
             |_____|
 +5V __/\/\___| | |____ out
           |    |
            -||-
            + 10u

There are some devices on the market, from different companies, sometimes
optimized for different IR burst frequencies.

Really great stuff!

  Lothar

1995\07\03@113250 by Benjamin Britt

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>
> I am working on a Basic Stamp project that detects IR from a
> standard tv remote control.  .....Should I scrap this idea, and use
> the GP1U52X IR receiver?
> Mike Brothers
> .....electronKILLspamspam.....wln.com

Hi Mike,

I did this for an IBM PC on a parallel port.  It was a NE555
-based transmitter and a GP1U52X receiver.  The receiver was
trivial using the module.  The bitstream from TV/VCR remotes
comes in at a very low rate but getting enough resolution from
the PC clock is a challenge.

I'd go for the GP1U52X approach.  It's easy to use, widely
available, and inexpensive.


Ben

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