Cheap RF communications

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!


Found a supplier ok - which is good!


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

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

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

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.


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.

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

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

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!