I have a question, about a RF 315/433 MHz Transmitter-receiver. Do any of you, know how to send multiple signals between the transmitter and receiver. And is there a guide on the internet for a newbie.
To turn off/on two relay remotely.
thank you in advance!
Hi, welcome to the forum.
There are so many possibilities, that I don't know where to begin.
Could you explain some more about the project.
For example : do you have multiple receivers or multiple transmitters ? is the communication in one direction, or in both directions using transceivers ?
I think you have a remote Arduino with two relays. In that case, transmit number 1 for relay 1 and number 2 for relay 2.
First of all, thanks for your reply!
I have two Arduino Uno and one RF transmitter and receive kit. (model number: MX-05V)
So far i have found out that i need a encoder and a decoder to send multiple signals, is that right?.
But my knowledge about encoding and decoding is minimal.
My plan is to make a motor that can rotate clockwise and counterclockwise by a relay. And if i can transmit more than two signals it will be a bonus.
The "trick" about radio communication is that it is - particularly at UHF frequencies - noisy and unreliable.
It is not all that practical to simply trust that if you transmit a signal, the receiver will detect it and if you do not transmit a signal, the receiver will not respond.
Other signals from a distance or just noise bursts from electrical interference or in fact, other nearby receivers which are often of the "superregenerative" type, can spuriously trip the receiver.
Therefore you transmit coded signals which are in some way reasonably unique and distinctive; you transmit them repeatedly and the receiver responds only to the correct code.
You can use encoder/ decoder chips for simple on/ off functions, but you can transmit serial data using the serial communications interface or "software serial" of the Arduino and use your own code such as sending "ON1" or "OFF1" and the like commands as serial text. Obviously, for the next "channel", you use "ON2" and "OFF2" and so on.
For safety, you can add a checksum to each message which must be correct for the command to be executed, and you can repeat the command a few times to make sure it is received. To be absolutely sure, you need to use a "duplex" system where replies can be sent back as well.
I had a go at this in the past, 433 is litered with interference, like Paul__B said, make sure that the code you send is unique and unlikely to be reproduced by chance,
I implemented a transmit code, then got the receiver to respond to it etc, to have varification of transmition,
you should consider a PING at a certain interval to ascertain if you still have the working RF link or not,
and also consider very carefully what will happen if the system goes wrong, IE the motor doesnt turn off when you send the code to do so.. or what happens if the motor turns on by mistake,
and when using relays, make sure that you investigate an H-bridge, you have to switch both the positive and negative leads of the motor in order to change direction,
your code should not allow both sides of the motor to become positive at once either,
Please take a look at using your modules with the VirtualWire library(or its current replacement RadioHead). Those libraries embody the best scheme for making these modules work correctly with maximum distance and error checking. You can certainly use these units to send and receive two different instructions.