On 6/3/2011 8:56 AM, Charles Craft wrote:
> On 6/3/2011 11:17 AM, Sean Breheny wrote:
>> Hi all,
>>
>> I am about to design a product which will be in use for at least 10
>> years and needs a medium range (about 50cm max) free-space optical
>> data link, low speed (under 9600 bps is fine - even 1200 bps would be
>> acceptable). The product contains both sides of the link so it does
>> not have to communicate with standard products. It needs to be robust
>> to a fair amount of dust (up to a 1cm layer of paper dust) and be able
>> to work in normal ambient room light (i.e., not outdoors).
>>
>>
> Is that 1cm or 1mm of dust?
> Did my wife send you the specs for my office?
There is an almost-hidden defect in the IRDA module that is often=20
overlooked: loss of
IR emitter intensity over time. If you need 10+ years of life, IRDA is=20
the wrong device unless it is
used infrequently, like taking a meter  reading, or checking status=20
monthly, etc.

Every time I tried to use an IRDA or a TV-style IR remote system, I was=20
foiled by one thing
or another. Mostly the problem was loss of distance in sunlight. Works=20
to 50m at night but
in daylight you are lucky to have one meter of distance.

--Bob A
--=20
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