I've played around with those sparkfun transmitter/receivers. the biggest problem is that what you send isn't always what you get, so you'll need to implement some sort of error correction or multiple message protocol. I eventually went to modules that have error correction built in. They're more expensive. DougM On Wed, Oct 12, 2011 at 8:11 AM, Joe Wronski w= rote: > On 10/11/2011 11:16 PM, V G wrote: >> Hi all, >> >> 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. >> >> 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? >> >> Xbee is cool, but it will add $40 at least to the cost of the project. >> >> Any other ideas? > I'm curious, why is encryption an issue? =A0Who, within 400 ft of your > garage, and with the receiver to read the signals, would care about the > state of the door? > As for interference, low data volume and low update frequency stuff like > this spends very little time on the air. =A0 =A0You could send one or mor= e > 10 mS burst at some fairly large interval (minutes) and be reasonably up > to date with the door. =A0 That shouldn't be a problem unless it > interferes with something that is data critical. > > Joe W > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .