On 7/3/2013 2:36 PM, Dwayne Reid wrote:
> - multiple systems can exist in the same area without interacting
> - new transmitter modules can be added to a system at any time
> - it would be best if individual transmitters could be identified somehow
> - batteries last at least one year
> - work in heat and cold (+50 to -40 C)
> - withstand very high vibration
> - range of at least 100 feet when in close proximity to large metal
> objects.  The face of the enclosure is always exposed to open air but
> that direction is pointing away from the receiver.
> - FCC *and* Industry Canada approval greatly desired
> - preferably in the 915 MHz ISM band, would consider other
> frequencies.  Prefer NOT to use 2.4GHz band.
>

Two things I see that make it hard are the battery life requirement and=20
the FCC approval, you need a module that is already cleared by FCC and=20
that is going to increase the cost a bit. May want to check into what=20
other frequencies are in use for the target site.

You can get the 433Mhz modules cheap , like these:
http://www.eeant.com/transmitter-receiver-module/

If this isn't going to be something you need future supplies for then=20
look around for some of the Chipcon modules. I found some last month=20
that were $5 each with antennas , guy only had 2 . Chipcon was bought by=20
TI so the old stocked stuff is selling cheap even though TI still=20
supports the parts, just changing them to the TI logos.

The operating near metal issue is going to be a problem with anything=20
you find, something you will have to solve antenna-wise.

Mark






--=20
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