Cheap RF communications

Forum 2005-2010 (read only) Hardware Interfacing
#1

Hi Guys,

Have a really good idea for a project - I (will) have 4 arduinos 1 master reciever and 3 slaves which need to communicate over RF, maximum of 100ft range.

There is no high speed data communication required so 2400bps would be plenty, needs to be quite a cost focus on the project but the sparkfun jobs below look quite good.

The only challenge I have is (I think) which slave is sending the data - my guess would be to send an initial string to the the master which identifies which slave it is?

Any input would be greatly appreciated - as would a UK supplier for something like the sparkfun modules linked!

G.

#2

http://www.coolcomponents.co.uk/catalog/product_info.php?cPath=25&products_id=186

Found a supplier ok - which is good!

G.

#3

You'll need to think carefully about how you organise the slaves such that only one slave transmits at a time.

#4

I would suggest having the master poll each slave for data.

In this manner, the slaves should only talk when talked to.

#5

Having the master poll the slaves, requires recievers in each of the slaves which will start making it more pricey - need to do the sums to work out if it will be too pricey.

Do they do 433 TX/RX combined units?

The chance of more than 1 slave sending data at one time is pretty slim - interesting problem though.

G.

#6

Didn't realize you were looking at transmit only on the slaves. (Guess I should have looked at the link!)

Without a receiver you will have no way to even tell if the data collided with another slave & retransmit.

The only other way I can think of to handle it would be to have the slaves transmit on a schedule. However, if there is any drift in the timing, you'll end up colliding all of the time.

Sorry I couldn't offer you a solution.

#7

If the slaves transmit on a low duty cycle (and perhaps repeat) they can communicate with high probability.

#8

The message from the slave should be sent several times with random intervals.

#9

there is a guy on ebay which sells dr3100's which he brings back from austrilia. they're tranciever modules. 100 ft might be pushing it a bit, but he does provide a hint on how to increase the range above leagal limits! they cost around £5. i'll find his ebay username out when i'm at home.

there is a guy whos written a library for this and other 433 rf units. its on the play ground some where, but i havn't actually tried it yet!

ps sorry it this is a bit illedgable, but i've written it on my phone!

#10