bus arrival information system - doubt regarding rf

[sankar mass]

friends , my projects is to display bus name through lcd display in bus stop when it coming at a certain distance approximately 80m using rf transmitter(in bus ) and receiver(in bus stop ) . I'm facing two problems .
1. when two bus came simultaneously. receiver couldn't receive data . i want to transmit two signals .

2. program idea or steps to do for above project. I'm using pic16f877

 

[dougy83]

Why can't receiver receive two signals? Are you proposing to transmit continuously?

The simple approach is to transmit a short signal from the transmitters with a random gap between each transmission. That way it's less likely that signals from multiple transmitters will collide, and if they do, it's even more unlikely that they'll collide a second time.

 

[sankar mass]

thank you sir . how can i transmit signals with a random time? for that what i have to use ?

 

[dougy83]

What are use using now?

 

[sankar mass]

sir I'm just using two rf transmitter and a rf receiver . my friend suggest me to use 555 timer to set delay .

 

[Nigel Goodwin]

thank you sir . how can i transmit signals with a random time? for that what i have to use ?

You simply write it in to the code of the processor you're using - if you're not using a processor, then you should be.

 

[sankar mass]

ya I'm using pic16f877 for my project. it used to display bus name by searching in look up table . but not with rf. can you suggest some model circuit or how to do ?

 

[dougy83]

The transmitter should use something to encode the signal also. You can use a microcontroller to do that. The delay can be put into the transmitter's microcontroller code while you're at it.

 

[sankar mass]

friends , i have to stop receiving signals from transmitter placed in bus after crossing the bus stop . how can i do it ? suggest me some ideas .

 

[sankar mass]

s sir you are correct . i am using two buses . if i set delay for two buses. wat can i do if they start /stop transmitting at same time

 

[Nigel Goodwin]

s sir you are correct . i am using two buses . if i set delay for two buses. wat can i do if they start /stop transmitting at same time

You simply have them transmit multiple times, with random time intervals in between.