IR Receiver/Demodulator [Design]

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From: Joerg on 18 Mar 2010 18:49

Phil Hobbs wrote:
> On 3/18/2010 5:59 PM, Hammy wrote:
>> On Thu, 18 Mar 2010 20:53:49 -0000, "markp"<map.nospam(a)f2s.com>
>> wrote:
>>
>>>
>>> "Hammy"<spam(a)spam.com> wrote in message
>>> news:j315q5t6flb0o0nemdrv2ngh5ig9jjesc8(a)4ax.com...
>>>> On Thu, 18 Mar 2010 19:29:49 GMT, Jan Panteltje
>>>> <pNaonStpealmtje(a)yahoo.com> wrote:
>>>>
>>>>> On a sunny day (Thu, 18 Mar 2010 12:11:21 -0500) it happened "eeboy"
>>>>> <jason(a)n_o_s_p_a_m.n_o_s_p_a_m.jasonorsborn.com> wrote in
>>>>> <woydnU4jer8kwz_WnZ2dnUVZ_oadnZ2d(a)giganews.com>:
>>>>>
>>>>>>
>>>>>> Spent a day playing around with the optics which yielded no major
>>>>>> improvements.
>>>>>
>>>>> I wanted to say this before, it is a weird thread, but at that
>>>>> distance
>>>>> use a 430 MHz transmitter receiver module.
>>>>
>>>> http://canada.newark.com/microchip/mrf49xa-i-st/rf-transceiver-ic/dp/08R1857?Ntt=MRF49XA-I/ST
>>>>
>>>
>>> Or if you wanted to avoid the impedance matching stuff and layout
>>> issues use
>>> the RFM12B module. Similar price, good performance. That module is
>>> available
>>> in 868 and 915MHz variants as well with a minor firmware change.
>>> Actually
>>> this Microchip part seems identical to the Si4421 chip used on the
>>> RFM12B
>>> with just some signal name changes!
>>>
>>> Mark.
>>>
>> The data sheet comes with a layout and BOM.
>>
>> But frankly I don't understand why he's only getting 8 ft range. I've
>> never tested mine in direct sunlight but I know at dawn/ dusk I get a
>> helluva lot further then that.
>>
>> Even if you Google IRDA ,IR BEAM etc. you'll find all sorts of
>> examples of people getting hundreds of feet transmission distance with
>> no special optics. A fresnel lens diffuses so I don't think that's
>> helping for one.
>>
>> As for an IR lens that filters out sunlight and other wavelengths just
>> rip one out of an old TV,STEREO whatever. All IR remote devices in my
>> house have a filter lens in front of the detector. I'm sure you could
>> find a scrap TV or something to scavenge one off for testing.
>>
>> I recall finding sources for the lens you can get it in strip form. I
>> cant find the site anymore but its inexpensive.
>
> You can go for miles and miles in the dark, if your aiming is good
> enough. During the day, even if you get rid of the DC, you're still
> buried by the shot noise of the sunlight. It's horrendous. Try
> calculating your expected noise floor--it isn't hard, and it's very
> instructive.
>

Well, at least he could get rid of some of that if he mounts a snippet
of tube in front of the photodiode. I've seen hangar doors where a
rather crude light sense scheme worked reliably. Ok, not 80ft but at
least 40ft.

--
Regards, Joerg

http://www.analogconsultants.com/

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

From: Phil Hobbs on 18 Mar 2010 18:53

On 3/18/2010 6:26 PM, Joerg wrote:
> Phil Hobbs wrote:
>> On 3/18/2010 5:18 PM, Martin Brown wrote:
>>> Jan Panteltje wrote:
>>>> On a sunny day (Thu, 18 Mar 2010 12:11:21 -0500) it happened "eeboy"
>>>> <jason(a)n_o_s_p_a_m.n_o_s_p_a_m.jasonorsborn.com> wrote in
>>>> <woydnU4jer8kwz_WnZ2dnUVZ_oadnZ2d(a)giganews.com>:
>>>>
>>>>> Spent a day playing around with the optics which yielded no major
>>>>> improvements.
>>>>
>>>> I wanted to say this before, it is a weird thread, but at that
>>>> distance use a 430 MHz transmitter receiver module.
>>>
>>> I agree. That or one of the generic cheap model car control modules
>>> which claim ranges roughly in the right ball park. Without error
>>> correction on the data sent this thing is headed for a fairly major
>>> train wreck.
>>>
>>> Meade stock was once pumped up in the .com (con) boom on the basis of
>>> high bandwidth building to building coms using 8" SCTs as the optics.
>>>
>>> http://www.space.com/businesstechnology/business/meade-telescope_000317.html
>>>
>>>
>>>
>>> Regards,
>>> Martin Brown
>>
>> Terabeam, RIP. I recently bought 75 of their beautiful 1.3 um APD/TIA
>> modules for about 75 cents apiece--probably half a cent on the dollar.
>>
>
> Sometimes this stuff seems to work though:
>
> http://www.modulatedlight.org/Dollars_vesus_Decibels_colour.pdf
>

You posted that the last time this came up. It's a great read. I
really don't know why it is so hard to get people to do simple photon
budget calculations even when their livelihood depends on the results.

Anxiety, I suppose....but surely it's better to find a good design
easily than beat your head against a brick wall (e.g. the shot noise of
sunlight).

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: Hammy on 18 Mar 2010 19:03

On Thu, 18 Mar 2010 22:30:24 -0000, "markp" <map.nospam(a)f2s.com>
wrote:

><snip>
>
>It does, but maybe you'd rather not do it. The RFM12B is available at about
>$2.10 in 1000off and has already been compliance tested, it lowers risk that
>the final product is compliant. You'd still need the BOM parts with the
>MRF49X in addition to the chip and get them placed on the PCB. In larger
>quantities the MRF49X solution might be more cost effective, but I don't
>think there's much in it.
>
>Mark.
>
I agree if your doing it for a commercial product in quantity you are
far better of get a fully assembled and compliant module. I don't
think that's the case here though.

Theres been some discussion here about RF compliance testing I dont
remember exact figures but it wasnt cheap. You would have to sell a
lot of your product just to recoup the testing cost. Not to mention
time and expensive RF test equipment....

I did get a couple of them though. I like to play;-)

From: Joerg on 18 Mar 2010 19:18

Phil Hobbs wrote:
> On 3/18/2010 6:26 PM, Joerg wrote:
>> Phil Hobbs wrote:
>>> On 3/18/2010 5:18 PM, Martin Brown wrote:
>>>> Jan Panteltje wrote:
>>>>> On a sunny day (Thu, 18 Mar 2010 12:11:21 -0500) it happened "eeboy"
>>>>> <jason(a)n_o_s_p_a_m.n_o_s_p_a_m.jasonorsborn.com> wrote in
>>>>> <woydnU4jer8kwz_WnZ2dnUVZ_oadnZ2d(a)giganews.com>:
>>>>>
>>>>>> Spent a day playing around with the optics which yielded no major
>>>>>> improvements.
>>>>>
>>>>> I wanted to say this before, it is a weird thread, but at that
>>>>> distance use a 430 MHz transmitter receiver module.
>>>>
>>>> I agree. That or one of the generic cheap model car control modules
>>>> which claim ranges roughly in the right ball park. Without error
>>>> correction on the data sent this thing is headed for a fairly major
>>>> train wreck.
>>>>
>>>> Meade stock was once pumped up in the .com (con) boom on the basis of
>>>> high bandwidth building to building coms using 8" SCTs as the optics.
>>>>
>>>> http://www.space.com/businesstechnology/business/meade-telescope_000317.html
>>>>
>>>>
>>>>
>>>>
>>>> Regards,
>>>> Martin Brown
>>>
>>> Terabeam, RIP. I recently bought 75 of their beautiful 1.3 um APD/TIA
>>> modules for about 75 cents apiece--probably half a cent on the dollar.
>>>
>>
>> Sometimes this stuff seems to work though:
>>
>> http://www.modulatedlight.org/Dollars_vesus_Decibels_colour.pdf
>>
>
> You posted that the last time this came up. It's a great read. I
> really don't know why it is so hard to get people to do simple photon
> budget calculations even when their livelihood depends on the results.
>
> Anxiety, I suppose....but surely it's better to find a good design
> easily than beat your head against a brick wall (e.g. the shot noise of
> sunlight).
>

Sometimes referred to as "sunlight noise", like on page 8 under
"calculated noise performance":

http://www.daxia.com/bibis/uploadasp/flies/IRDA%B1%EA%D7%BC%A3%BAVFIR%CE%EF%C0%ED%B2%E3%B9%E6%B7%B6.pdf

--
Regards, Joerg

http://www.analogconsultants.com/

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

From: Hammy on 18 Mar 2010 19:47

On Thu, 18 Mar 2010 18:22:23 -0400, Phil Hobbs
<pcdhSpamMeSenseless(a)electrooptical.net> wrote:

>
>You can go for miles and miles in the dark, if your aiming is good
>enough. During the day, even if you get rid of the DC, you're still
>buried by the shot noise of the sunlight. It's horrendous. Try
>calculating your expected noise floor--it isn't hard, and it's very
>instructive.
>
>Cheers
>
>Phil Hobbs

I realize you aren't going to get hundreds of meters range in the day
but you should be able to get better then 8'.

They use IR for laser tag. I don't know what the military uses I'm
guessing IR as well for their war games. These are used during the
day.So it can be done. They also use proper optics to focus the beam
you would have to point the emitter at the detector for reliable
50-200m range transmission.

The only way you are going to get reliable 50-200m range daytime
transmission is with optics and aiming at the receiver which is
shielded as much as practical from the sunlight using the LENS
mentioned and mechanical methods like a tube.

Frankly for daytime I think you would be better off using a 433MHz RF
module. For nighttime line of sight IR would be simpler and cheaper
but for transmission day and night RF would be the most reliable.