How can I give a unique id for each transmitter ?

Thread Starter

Dohab

Joined Oct 17, 2009
9
I don´t know where you read that, but I don´t really think that´s true. The practical distance depends on the sensitivity of the receiver and reflections in the room.
as a beginner or less, I was looking in tutorials sites :D

You definitely need some kind of receiver in the transmitters, because you need to get some kind of synchronisation between them, to make them all send at the same time.
You could use infrared light instead of RF for the trigger, but that will again introduce risk of blocking the sensor and not firing when it should.
I was planning to deal with each transmitter as if it transmits alone, then later in a " Reader " program, I will place them depending on how far they were from the 3 receivers.
that was my idea when I thought of using the same frequency anyway.

For making them send at the same time, I was thinking of using one chip of 555 which is connected to them, don't you agree?

as you explained, Infrared is useless in our case.

If you want to give this a try, make two ultrasound transmitters, each generating some kind of tone, and try to receive it with one receiver. To keep it simple, connect the transmitter by wires, place them at a typical distance from the receiver, and start trying to distinguish which one came first, and the exact times of arrival for each one.
I'll try that indeed.

But you have to excuse me,
What did you mean by " kind of tone " ?
I don't understand how can I tell which tone is belong to which transmitter?

BTW: Is there any quick yet perfect explanation about encoding/decoding Subject, and how can it be done?
I've looked everywhere!

thanks a lot.
 

kubeek

Joined Sep 20, 2005
5,794
Not soure about the frequency band of the transmitter-receiver pair, but you can try for example one transmitting a burst of sine wave at 25khz and the other at 1ms later 35khz. On the receiver you get a mix of the two frequencies, and you need to find if it is possible to tell the time each arrived. Then you have to find how close apart the waves can be, how close to perfection you can get this.

The 555 timer will never get the needed accuracy, and not even a crystall oscillator will make all the transmitters transmit at the exact same time, or just a few us apart. You need to provide some sychronisation to be able to tell the distance.

ETA: now I thought that you don´t actually need to have them all transmit at the same time, you can have them transmitting in a sequence, by sending a request to each one to start transmitting. But a receiver is a necessity anyway.
 
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