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From: PeterD on 17 Mar 2010 08:46
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:

> simply pulses of varying length (20ms-80ms). These
>pulses occur at the rate of approximately 1Hz.

Wonder what 60Hz 'humm' has for a width?

>It is important that the
>pulse length is preserved from transmitter to receiver. In other words, if
>I send a 20ms pulse I expect it to be within 5% on the receiving side. The
>sensor will be used outdoors so it must discriminate against ambient IR and
>other sources (street lights?).

You'll have to filter the line frequency out.

>I'd like to have a fairly high Q such that
>'normal household remotes' operating around 38kHz are significantly
>attenuated. Finally, given the device is battery powered (5V regulated) it
>should consume little power (sub 1mA if possible)
>
>I've tried using a simple IR remote receiver module (Vishay PN
>TSOP85238TR). They work great indoors (~50') but are lousy outside (~8').

More power from your LED emitter?

>
From: markp on 17 Mar 2010 12:10

"eeboy" <jason(a)n_o_s_p_a_m.n_o_s_p_a_m.jasonorsborn.com> wrote in message
news:Y8KdncE5WexRKD3WnZ2dnUVZ_jednZ2d(a)giganews.com...
>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
> pulses occur at the rate of approximately 1Hz. It is important that the
> pulse length is preserved from transmitter to receiver. In other words, if
> I send a 20ms pulse I expect it to be within 5% on the receiving side. The
> sensor will be used outdoors so it must discriminate against ambient IR
> and
> other sources (street lights?). I'd like to have a fairly high Q such that
> 'normal household remotes' operating around 38kHz are significantly
> attenuated. Finally, given the device is battery powered (5V regulated) it
> should consume little power (sub 1mA if possible)
>
> I've tried using a simple IR remote receiver module (Vishay PN
> TSOP85238TR). They work great indoors (~50') but are lousy outside (~8').
>
> Now, I am not an analog guru which is why I am here to seek guidance. My
> initial thoughts were to amplify and filter (bandpass) using op-amps.
> However, I started googling to see what I could find on the subject and
> nearly everything I found was contrary to my initial thoughts. So,
> obviously I am not thinking correctly! :) However, the types of circuits I
> was finding are quite puzzling to me. For example, take this circuit:
> http://www.discovercircuits.com/PDF-FILES/4069rvr.pdf . Seems simple
> (based
> on component count) although I don't quite understand how the center
> frequency is set using the inductor and resistor. But why CD4069UB? I've
> never seen them used as linear amplifiers before. And 2H isn't really that
> practical eh?
>
> Taking my requirements into account, what might be the best way to
> proceed?
>

The 'UB' part of the CD4069 stands for 'un-buffered'. In that configuration
the have high gain and can be used in a linear mode. These are very often
used as the inverting feedback amplifier in crystal oscillators.

You'd be better off IMO in using a high Q bandpass circuit made from two or
more opamps. Google is your friend, here's an example:
http://www.vidyasagar.ac.in/journal/maths/Vol11/JPS11-16.pdf

The higher the Q the better I think as you've got quite a lot of background
noise.

Mark.


From: Phil Hobbs on 17 Mar 2010 12:22
On 3/17/2010 12:10 PM, markp wrote:
> "eeboy"<jason(a)n_o_s_p_a_m.n_o_s_p_a_m.jasonorsborn.com> wrote in message
> news:Y8KdncE5WexRKD3WnZ2dnUVZ_jednZ2d(a)giganews.com...
>> 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
>> pulses occur at the rate of approximately 1Hz. It is important that the
>> pulse length is preserved from transmitter to receiver. In other words, if
>> I send a 20ms pulse I expect it to be within 5% on the receiving side. The
>> sensor will be used outdoors so it must discriminate against ambient IR
>> and
>> other sources (street lights?). I'd like to have a fairly high Q such that
>> 'normal household remotes' operating around 38kHz are significantly
>> attenuated. Finally, given the device is battery powered (5V regulated) it
>> should consume little power (sub 1mA if possible)
>>
>> I've tried using a simple IR remote receiver module (Vishay PN
>> TSOP85238TR). They work great indoors (~50') but are lousy outside (~8').
>>
>> Now, I am not an analog guru which is why I am here to seek guidance. My
>> initial thoughts were to amplify and filter (bandpass) using op-amps.
>> However, I started googling to see what I could find on the subject and
>> nearly everything I found was contrary to my initial thoughts. So,
>> obviously I am not thinking correctly! :) However, the types of circuits I
>> was finding are quite puzzling to me. For example, take this circuit:
>> http://www.discovercircuits.com/PDF-FILES/4069rvr.pdf . Seems simple
>> (based
>> on component count) although I don't quite understand how the center
>> frequency is set using the inductor and resistor. But why CD4069UB? I've
>> never seen them used as linear amplifiers before. And 2H isn't really that
>> practical eh?
>>
>> Taking my requirements into account, what might be the best way to
>> proceed?
>>
>
> The 'UB' part of the CD4069 stands for 'un-buffered'. In that configuration
> the have high gain and can be used in a linear mode. These are very often
> used as the inverting feedback amplifier in crystal oscillators.
>
> You'd be better off IMO in using a high Q bandpass circuit made from two or
> more opamps. Google is your friend, here's an example:
> http://www.vidyasagar.ac.in/journal/maths/Vol11/JPS11-16.pdf
>
> The higher the Q the better I think as you've got quite a lot of background
> noise.
>
> Mark.
>
>

Trying to cheap out on a demanding photoreceiver design is not a very
productive approach. To get good results you really have to do some
calculations, I'm afraid.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
From: John Larkin on 17 Mar 2010 12:24
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
>pulses occur at the rate of approximately 1Hz. It is important that the
>pulse length is preserved from transmitter to receiver. In other words, if
>I send a 20ms pulse I expect it to be within 5% on the receiving side. The
>sensor will be used outdoors so it must discriminate against ambient IR and
>other sources (street lights?). I'd like to have a fairly high Q such that
>'normal household remotes' operating around 38kHz are significantly
>attenuated. Finally, given the device is battery powered (5V regulated) it
>should consume little power (sub 1mA if possible)
>
>I've tried using a simple IR remote receiver module (Vishay PN
>TSOP85238TR). They work great indoors (~50') but are lousy outside (~8').
>
>Now, I am not an analog guru which is why I am here to seek guidance. My
>initial thoughts were to amplify and filter (bandpass) using op-amps.
>However, I started googling to see what I could find on the subject and
>nearly everything I found was contrary to my initial thoughts. So,
>obviously I am not thinking correctly! :) However, the types of circuits I
>was finding are quite puzzling to me. For example, take this circuit:
>http://www.discovercircuits.com/PDF-FILES/4069rvr.pdf . Seems simple (based
>on component count) although I don't quite understand how the center
>frequency is set using the inductor and resistor. But why CD4069UB? I've
>never seen them used as linear amplifiers before. And 2H isn't really that
>practical eh?

It's a bizarre circuit.

Some things that would help you:

1. Maximize optical path gain, which means using lenses or equivalant
to focus the transmitter and receiver at one another and exclude as
much ambient light as possible from entering the receiver.

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

3. Dump the photodiode current into a tuned LC tank and amplify that
with a very low-noise device, probably a jfet. The 4069 will be about
the noisiest and least gain-predictable amplifier you can buy for a
reasonable amount of money. An LC to ground allows a lot of ambient
light signal to get dumped without saturating any amplifier stages.

4. Increase transmit power.

5. Buy Phil Hobbs' book


The problem with using a high-Q resonator is making sure it's on
frequency, and not over-doing Q to the point that the data rate is
compromised.

What's the application?

John

From: Joerg on 17 Mar 2010 12:40
John Larkin 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
>> pulses occur at the rate of approximately 1Hz. It is important that the
>> pulse length is preserved from transmitter to receiver. In other words, if
>> I send a 20ms pulse I expect it to be within 5% on the receiving side. The
>> sensor will be used outdoors so it must discriminate against ambient IR and
>> other sources (street lights?). I'd like to have a fairly high Q such that
>> 'normal household remotes' operating around 38kHz are significantly
>> attenuated. Finally, given the device is battery powered (5V regulated) it
>> should consume little power (sub 1mA if possible)
>>
>> I've tried using a simple IR remote receiver module (Vishay PN
>> TSOP85238TR). They work great indoors (~50') but are lousy outside (~8').
>>
>> Now, I am not an analog guru which is why I am here to seek guidance. My
>> initial thoughts were to amplify and filter (bandpass) using op-amps.
>> However, I started googling to see what I could find on the subject and
>> nearly everything I found was contrary to my initial thoughts. So,
>> obviously I am not thinking correctly! :) However, the types of circuits I
>> was finding are quite puzzling to me. For example, take this circuit:
>> http://www.discovercircuits.com/PDF-FILES/4069rvr.pdf . Seems simple (based
>> on component count) although I don't quite understand how the center
>> frequency is set using the inductor and resistor. But why CD4069UB? I've
>> never seen them used as linear amplifiers before. And 2H isn't really that
>> practical eh?
>
> It's a bizarre circuit.
>
> Some things that would help you:
>
> 1. Maximize optical path gain, which means using lenses or equivalant
> to focus the transmitter and receiver at one another and exclude as
> much ambient light as possible from entering the receiver.
>

1b. Don't forget the simplest of all ambient light protectors: A piece
of pipe in front of the photodiode.


> 2. Put a narrowband optical filter in front of the receiver to pass
> the optical signal and reject wideband ambient light.
>
> 3. Dump the photodiode current into a tuned LC tank and amplify that
> with a very low-noise device, probably a jfet. The 4069 will be about
> the noisiest and least gain-predictable amplifier you can buy for a
> reasonable amount of money. An LC to ground allows a lot of ambient
> light signal to get dumped without saturating any amplifier stages.
>

CD4000 chips actually aren't all that bad as linear amps.


> 4. Increase transmit power.
>

Yup. Consider pulsing where peak power can be a whole lot higher than
CW, using the same IR emitter.


> 5. Buy Phil Hobbs' book
>
>
> The problem with using a high-Q resonator is making sure it's on
> frequency, and not over-doing Q to the point that the data rate is
> compromised.
>

Crystals have already been mentioned. They are always on frequency but
in really cold climates they might seize up.


> What's the application?
>

I wonder if it couldn't be done via radio link.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
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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.