RF Link

Aerocom and someone else does that too, but IIRC Linx isn't FHSS, is it?

What's your data rate? If you only need up to say, 2400 baud, maybe

Check this out:

-- "Everything is interrelated - because it has to be. Experience is just energy, and energy cannot be created nor destroyed." MCJ 20050119

Well here is the dilemma... I need to know if object A is too far from object B, and if so will send a "1" to the chip in A. I was told that RFID is the only technology avaible to do this easily, but RFID is way too expensive to implement at this point. I was hoping to find another low cost RF solution.

Well, there are several things you could try. The easiest would probably be a simple low-power RF signal generator, which only puts out enough power to be measureable from your "good" distance. This has the disadvantage that simple obstructions may give a false "too far" result of your receiver.

An other idea, much more involved, would be to send an RF pulse from B to A and back to B, measuring the delay in nanoseconds. You perhaps could do this with a fast microcontroller chip - enable interrupts, send RF pulse, start timer -->

interrupt happens, stop timer, timer value = delay. Since the speed of RF in air is known, the time taken to ping-pong an RF pulse back and forth between these two points can be turned into a physical distance.

Thanks for your ideas!

Sorry I have been out of this whole thing. Working 60 hours a week does not leave much time for well, anything. About the RF and RFID.

The reason that the system uses RF as well as RFID is as follows:

If the system were to use simply just RF TX/RX to test for the presence of the rider, the transmitter as well as the receiver would need to constantly be using power. Unfortunately we do not have a lot of power to work with on the jacket.

The benefit of using the RFID, although expensive, I believe is worth it. With RFID you can sense for the presence of the rider without using any power on the jacket. We can accomplish this by placing the RFID tag in the jacket and the reader on the bike. The tag uses absolutely zero power. The only power that would be being used would be by the RF TX/RX sitting in idle or standby. The RF in standby uses drastically less power than when it is actually transmitting or recieving.

Another downside to just using RF is that with such significant power consumption you are limited as to how long you can wear the jacket and have the system functional until the battery needs to be recharged/replaced. This can cause the system to fail for riders going on rides of more than a couple of hours. This is a huge safety issue.

I hope this helps and I will try to keep up with the questions and will add anything I can. Thanks guys.