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> On Oct 12, 2011, at 9:11 AM, Joe Wronski wrote:
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> On 10/11/2011 11:16 PM, V G wrote:
>> Hi all,
>>=20
>> I want to make a simple, cheap, quick, reliable (no one dare say you can
>> only pick only x) garage door open detector that will light up an LED in=
 the
>> house/beep a speaker if the garage door is open. I know all it takes is =
a
>> mechanical switch, but I'd rather not use any moving parts. I'm thinking=
 a
>> very bright infrared LED and IR transistor with a piece of foil mounted =
on
>> the inside of the garage door. If the door is closed, a series of LED pu=
lses
>> will hit the aluminum foil reflector and bounce back to the IR transisto=
r
>> and signal the device that the door is closed. Will this work? I've neve=
r
>> done any IR work, so I don't really know what power LED is required, wha=
t
>> the distances are, etc.
>>=20
>> As for the micro controller unit, I can make it wireless and signal the
>> indoor unit via something like this
>> http://www.sparkfun.com/products/10534but I'd have to impliment
>> encryption on the micro controller itself. It
>> would also interfere with other units in the same band, which is very ve=
ry
>> undesirable. How hard is it to implement simple encryption?
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>> Xbee is cool, but it will add $40 at least to the cost of the project.
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>> Any other ideas?
> I'm curious, why is encryption an issue?  Who, within 400 ft of your=20
> garage, and with the receiver to read the signals, would care about the=20
> state of the door?
> As for interference, low data volume and low update frequency stuff like=
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> this spends very little time on the air.    You could send one or more=20
> 10 mS burst at some fairly large interval (minutes) and be reasonably up=
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> to date with the door.   That shouldn't be a problem unless it=20
> interferes with something that is data critical.
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> Joe W

If this is for fun ........ and a learning experience......
Use an Xbee pair of transceivers ( home and door ) .... send a serial strea=
m to the garage door transceiver  ... at the door use the serial stream to =
drive an infrared LED.  Use an infrared receiver to produce the same serial=
 stream back into the garage Xbee.  Then look for that stream at the home X=
bee.

Xbee could replaced by bluetooth modules or TI low power RF  ( CC115L trans=
mitter, CC113L receiver and CC110L transceiver ) or many other RF solutions=
..  I can say more if you are interested.
99guspuppet


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