IR Receiver/Demodulator [Design]

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From: Joerg on 18 Mar 2010 19:54

Hammy wrote:
> 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'.
>

He needs 80ft.

> 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.
>

It can be done. I know for sure ;-)

> 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.

433MHz is technically a piece of cake. But, and this is a _big_ but: If
you want very low cost you have to roll your own and then you must get
it blessed at an EMC lab. That comes with a high four-digit price tag
and only if you pass first time. If you need a mulligan you'll easily be
above $10k.

If you want to use pre-certed modules that's going to bump up the BOM
budget, big time.

--
Regards, Joerg

http://www.analogconsultants.com/

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

From: Dave Platt on 18 Mar 2010 19:18

In article <2p75q51q8ao2vt8o3vjmoal2c9gcuot9h1(a)4ax.com>,
Hammy <spam(a)spam.com> wrote:

>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.

Another option is to visit a store which sells sheet plastic (e.g. TAP
Plastics, Professional Plastics), dig through their scrap bin, and buy
as thin a piece of black acrylic plastic as you can find. This stuff
filters out visible light, but the dye in it passes a significant
amount of IR.

I've taken some interesting photos, using an old Fuji FinePix camera
whose Sony sensor has a less-than-efficient IR-exclusion filter,
shooting through a simple home-made filter made from black acrylic
glued to the end of PVC tubing. The results have the usual IR-photo
appearance - the sky is quite dark, green leaves on trees appear
almost white.

--
Dave Platt <dplatt(a)radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

From: Hammy on 18 Mar 2010 20:14

On Thu, 18 Mar 2010 16:54:38 -0700, Joerg <invalid(a)invalid.invalid>
wrote:

>
>He needs 80ft.

Then he is going to have to collimate the IR emitter and use an
optical filter optimized for his wavelength on the detector. It would
also be very directional.

>> 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.
>>
>
>It can be done. I know for sure ;-)
>
[snip]
>
>433MHz is technically a piece of cake. But, and this is a _big_ but: If
>you want very low cost you have to roll your own and then you must get
>it blessed at an EMC lab. That comes with a high four-digit price tag
>and only if you pass first time. If you need a mulligan you'll easily be
>above $10k.

Is that what it is for RF compliance testing I'd go broke;-).

>If you want to use pre-certed modules that's going to bump up the BOM
>budget, big time.

Given the cost of compliance testing it still might be cheaper to use
modules? Unless you have a really large mark-up or plan on moving them
in the 100k quantities.Particularly when you factor in assembly cost,
testing etc.

From: Phil Hobbs on 18 Mar 2010 20:24

On 3/18/2010 7:18 PM, Joerg wrote:
> 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
>
>
Yup, except those guys are using 10 uW/cm**2, which isn't easy to
achieve at any distance unless you're using lenses. They also assume 5
W/m**2 for sunlight, which means they're using a narrow optical
filter--full sun is more like 800 W/m**2.

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: Joerg on 18 Mar 2010 20:47

Hammy wrote:
> On Thu, 18 Mar 2010 16:54:38 -0700, Joerg <invalid(a)invalid.invalid>
> wrote:
>
>
>> He needs 80ft.
>
> Then he is going to have to collimate the IR emitter and use an
> optical filter optimized for his wavelength on the detector. It would
> also be very directional.
>

At the least he's got to put a piece of pipe up front. And yes, that
alone will already make it directional. There shouldn't be any daylight
hitting the photodiode directly.

>>> 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.
>>>
>> It can be done. I know for sure ;-)
>>
> [snip]
>> 433MHz is technically a piece of cake. But, and this is a _big_ but: If
>> you want very low cost you have to roll your own and then you must get
>> it blessed at an EMC lab. That comes with a high four-digit price tag
>> and only if you pass first time. If you need a mulligan you'll easily be
>> above $10k.
>
> Is that what it is for RF compliance testing I'd go broke;-).
>

Labs run $200-$300 per hour, depending on location. You might get a
slightly better deal in the boonies or when they are hungry.

>> If you want to use pre-certed modules that's going to bump up the BOM
>> budget, big time.
>
> Given the cost of compliance testing it still might be cheaper to use
> modules? Unless you have a really large mark-up or plan on moving them
> in the 100k quantities.Particularly when you factor in assembly cost,
> testing etc.

That's why a lot of stuff that could be done via RF isn't. Modules are
quite expensive and some of them are IMHO not very well engineered.

--
Regards, Joerg

http://www.analogconsultants.com/

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