IR Receiver/Demodulator [Design]

Prev: Microeconomics 5e Jeffrey M. Perloff test bank and solution manual is available for purchase at affordable prices. Contact me at alltestbanks11[at]gmail.com to buy it today.
Next: Essentials of the Legal Environment 2nd Edition 2008 Roger LeRoy Miller Test bank is available for purchase at affordable prices. Contact me at alltestbanks11[at]gmail.com to buy it today.

From: Martin Brown on 17 Mar 2010 18:52

mpm wrote:
> On Mar 17, 11:24 am, John Larkin
> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote:
>> On Wed, 17 Mar 2010 05:58:20 -0500, "eeboy"

>> <jason(a)n_o_s_p_a_m.n_o_s_p_a_m.jasonorsborn.com> wrote:
>>> I need to design an IR receiver which will demodulate IR input at a given
>>> carrier frequency (~32kHz) over distances of 60-80 feet. I am not
>>> transmitting data, simply pulses of varying length (20ms-80ms). These

>> 2. Put a narrowband optical filter in front of the receiver to pass
>> the optical signal and reject wideband ambient light.

> #2 was the first thing I thought about too.
>
> Mainly, because earlier today, I purchased a new camera lens (a 500mm
> mirrror), and I always make it a point to grab a couple Roscolux
> swatchbooks while I'm at it.
> Such as this one from BHPhoto:
> http://www.bhphotovideo.com/c/product/45189-REG/Rosco_950SBLUX0103_Roscolux_Swatchbook.html
>
> Hard to beat at $1.95 each.
> I wonder if there's a gel in there that will do the job?

Probably not - most of them are intended for stage and photo studio
lighting.

Kodaks Wratten 87 is a generic IR pass filter. For a quick and dirty
trial unexposed and developed slide film is usable. But you could do
better with a dedicated long pass IR filter like Schott RG800 or RG850
(or much cheaper cast plastic IR dye filters).

Narrow bandpass interference filters can get expensive. Laser line tuned
ones 10nm fwhm are about the cheapest at ~�50.

Regards,
Martin Brown

From: eeboy on 17 Mar 2010 19:20

>
>Probably not - most of them are intended for stage and photo studio
>lighting.
>
>Kodaks Wratten 87 is a generic IR pass filter. For a quick and dirty
>trial unexposed and developed slide film is usable. But you could do
>better with a dedicated long pass IR filter like Schott RG800 or RG850
>(or much cheaper cast plastic IR dye filters).
>
>Narrow bandpass interference filters can get expensive. Laser line tuned
>ones 10nm fwhm are about the cheapest at ~�50.
>

The TSOP module is encased in a black plastic resin (and so is the pin
photodiode that I have for that matter). Isn't the purpose of that for
creating an optical filter which passes only the band of interest?

---------------------------------------
Posted through http://www.Electronics-Related.com

From: Tim Williams on 17 Mar 2010 21:28

"eeboy" <jason(a)n_o_s_p_a_m.n_o_s_p_a_m.jasonorsborn.com> wrote in message
news:RPudnc5Rtf9J_jzWnZ2dnUVZ_tCdnZ2d(a)giganews.com...
> The TSOP module is encased in a black plastic resin (and so is the pin
> photodiode that I have for that matter). Isn't the purpose of that for
> creating an optical filter which passes only the band of interest?

Not having any IR LEDs at the time, I once used a red superbright.
Planted directly in front of the photodiode (alignment was fairly
critical) and pulsed at 100mA (more than a few Cd worth), I got a
usable signal out of the diode. :-)

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

From: mike on 17 Mar 2010 21:59

eeboy wrote:
>> Probably not - most of them are intended for stage and photo studio
>> lighting.
>>
>> Kodaks Wratten 87 is a generic IR pass filter. For a quick and dirty
>> trial unexposed and developed slide film is usable. But you could do
>> better with a dedicated long pass IR filter like Schott RG800 or RG850
>> (or much cheaper cast plastic IR dye filters).
>>
>> Narrow bandpass interference filters can get expensive. Laser line tuned
>> ones 10nm fwhm are about the cheapest at ~�50.
>>
>
> The TSOP module is encased in a black plastic resin (and so is the pin
> photodiode that I have for that matter). Isn't the purpose of that for
> creating an optical filter which passes only the band of interest?
>
> ---------------------------------------
> Posted through http://www.Electronics-Related.com
You haven't given much detail, but this is beginning to look like a
very bad idea.

You're trying to detect a tiny signal in a sea of high intensity noise.
What are you using for error detection/correction?
Small percentage modulation of the ambient light can wreak havoc with your
input amplifiers. Reflection from passing car, shadow from bird flying
overhead,
bee flying thru the signal path can all saturate your amps long
enough to trash the pulse width measurement.

If it's a handheld remote, you've got lots of other issues.
If it's fixed position on both ends,
have you considered 80 feet of wire?
Sometimes low-tech is best.

From: Martin Brown on 18 Mar 2010 04:18

eeboy wrote:
>> Probably not - most of them are intended for stage and photo studio
>> lighting.
>>
>> Kodaks Wratten 87 is a generic IR pass filter. For a quick and dirty
>> trial unexposed and developed slide film is usable. But you could do
>> better with a dedicated long pass IR filter like Schott RG800 or RG850
>> (or much cheaper cast plastic IR dye filters).
>>
>> Narrow bandpass interference filters can get expensive. Laser line tuned
>> ones 10nm fwhm are about the cheapest at ~�50.
>
> The TSOP module is encased in a black plastic resin (and so is the pin
> photodiode that I have for that matter). Isn't the purpose of that for
> creating an optical filter which passes only the band of interest?

Not really. It is a crude dye based long pass filter which cuts most but
not all of the visible light. Some have a nominal passband fwhm ~50nm at
950nm, but may still pass ~1% of deep read and 0.1% or so in the visible
tail which when you have incident sunlight is still a heck of a lot.

Easy enough to test it with a white LED torch to see how good the built
in filter is at blocking visible light. A layer of black slide film in
front might still give you some additional signal to noise.

Or alternatively put the thing out in full sun and measure its operating
point with and without a thick black cloth covering the sensor.

Regards,
Martin Brown