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Topic: ATTiny + Rf Module? (Read 5352 times) previous topic - next topic


I get annoyed by simple things - two things, right now, in particular.

1.  My lightswitch is like, 20 feet away from my bed.  I've got a string running on a pulley track made of pushpins across my wall, but that's annoying/inconvenient, and breaks semi-often.

2.  My car is old, and while it has internal door lock/unlock buttons, there aren't any remote ones.

Hopefully, you can see where this is leading to.  I want to make a remote - Ideally staying with inexpensive and low-power components.  I've looked at the sparkfun and seeed RF module kits (seeed here: http://www.seeedstudio.com/depot/315mhz-rf-link-kit-p-76.html), the seeed is less expensive, so I'd prefer to use that.

The remote will be as small as possible, probably powered ball a small lipo cell, still debating about that - rechargeable, a simple cr2032, something else, etc.

For the lightswitch, I've found a SPDT relay that can handle mains voltage, I'll hook it up in (a sort of) series with my current lightswitch, probably with the traveler system, and then I'd like to have a receiving module there hooked up to the relay via attiny to interpret the signal.  It'll all be powered pretty easily, I've got mains power right there, and transformers are cheap.

In my car, I'll probably just run it off the car battery, because the current draw will ideally be tiny.  I'd like it to also be just a receiver and an attiny to interpret/act ('press' the unlock or lock button), but I have a couple concerns:

1.  I'm new to RF - the simplest way for me to do it, as far as I've seen so far, is with virtualwire, which looks pretty easy to use.  That way, I could just have it send a different message for each command I want, depending on which button I pressed.  That way I don't accidentally turn my lights on/off when I'm unlocking or locking my car.  However, I don't know that virtualwire can run on an attiny.  What's my best bet here - just go with an atmega 168 or 328, pay the $4 extra each, and have it be more convenient/easy, or is there a simpler solution?

2.  Interference - from what I understand, that's a big problem.  I don't want some random interference unlocking my car, that would be BAD.  This is why I wanted to use virtualwire, because it's got (again, from what I understand) built-in checksums and stuff, so it's not likely that random interference will just happen to perfectly emulate a sent command+checksum.

Those are my main concerns right now.  If you have any general tips for me, or if you get the gist of what I'm saying/asking and know what I need (a little low on sleep, I'M not even sure what I'm trying to say right now).

... In conclusion, HELP WITH SECURE(ISH) RF ON ATTINY (OR SHOULD I NOT USE ATTINY?)! because I think that's what I've been trying to ask with the past 80 lines of text.  Man, I'm going to sleep.  Sorry you had to read that.



Get yourself some cheap RF power outlets and http://code.google.com/p/rc-switch/

This library also works with a cheap retrofitting unlock system for my car but it's not secure as anybody could sniff and replicate the RF signals. Conventional RF unlocking systems which require some security (=most genuine car locking systems) use a rolling code

You don't need to worry about interferences, as the signals are typically very specific binary 24bit values. It's nearly impossible that such a signal is received by fortune, so there is only a small chance of someone in your periphery who has a similar device sending the same codes.


Consider using this device: http://tinyurl.com/3hqtj6n

It could control an AC relay easily. You'd have to custom build or find available a relay operated door unlocking mechanism.

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