433 mhz Tx Rx same arduino

Hi all,

the title is a little misleading - I don't want to send & receive at the same time on the same Arduino; I've read that it's quite difficult to do that and it's not what I need.

I want to be able to use a receiver to catch the binary output (I believe these are 24 bit) from a 433mhz device - namely, remote control power sockets, store it, and then transmit it back out at a later time.

I have found these:

http://www.ebay.co.uk/itm/320841198302?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

on ebay.

Would these do the trick?

I can't find anything on which pins to use etc... although the listing claims that they will send documentation once purchased.

Is this possible with this kit do you think?

Your description is still a bit vague. But first I would suggest you do not use what you found on that link. You are looking for a transceiver setup. What you have there is a transmitter and a receiver in two separate components. This allows one way comms. This will not allow you to do two way comms.

There are many options available but if you are set on 433Mhz, I would look at the RFM12B through Sparkfun since there are a lot of people that have actually made these work.

I would be very leery of anything that you cannot find a datasheet on or google someone that has already used it at least once.

Try these with VirtualWire library.
http://www.robotshop.com/433mhz-high-sensitivity-transmitter-receiver-pair-rxa30.html

Hi guys, thanks for the replies.

I don't really need two-way communication per se., which is why I went for the transmitter/receiver route rather than the transceiver, although I guess either could work.

I want to press a button on my remote for say, my front door (I salvaged an electric, remote-controlled (433mhz) gate system from work after an attempted break in - I can now, press a key-fob and the front door unlocks), and record the output into the Arduino. After reading about in different forums/blogs etc..., there seems to be a de-facto standard of sending a OOK 24 bit binary key that pairs it with the device over 433 mhz for these types of applications. It's that key that I want to read into the Arduino.

Currently, I have a USB relay that is wired to short the switch in a spare key-fob that I have so I can control the opening of the door via a PC. I want to extend this system to include my wireless power sockets, but the housing box I have this stuff in is now getting quite large and it's not practical to keep shorting switches through USB relays out of a PC any longer. Every time I want to add something to the list, I have to break the remote and wire it out to a USB switch again. I'm trying to simplify the whole affair :wink:

After I've read the 24 bit key into the Arduino, I'd like to then take the reciever off of it and replace it with the transmitter so that I can tell the Arduino to transmit the same key that will unlock the front door.

Since posting, I found this: GitHub - sui77/rc-switch: Arduino lib to operate 433/315Mhz devices like power outlet sockets. which seems like a library to do what I'm asking. It suggests that as long as I get the correct chip-set then this all should be possible.

PS. Thank for the link, btw....although at $78 to deliver ONE! of those to the UK, I might have to look elsewhere! :wink:

$78 - I would look around more too!

Is this better?
http://www.robotshop.com/eu/productinfo.aspx?pc=RB-See-12&lang=en-US

You could also try ordering direct from seeed studio
http://www.seeedstudio.com/depot/433mhz-rf-link-kit-p-127.html?cPath=139_140

What you have to consider is how your remote device is encoding the data. It is all well enough having the same frequency, but the modulation format has to be the same as well.

The frequency of the receiver must match exactly the transmitter and a description of just 433MHz is just the band it is in it is not the exact frequency. You might be able to tune the receiver but most of them are crystal controlled.

Then when you find out if the modulation is AM or FM, you need to know if it is AFSK or FSK. Once you find out that you need to know how the data is encoded, for example bi-phase, Manchester encoding, NRZ and so on.

When all those match on the transmitter and receiver, you can think about reading in the data to the arduino.
It will help if you have access to some test equipment that can look at that frequency.

I believe VirtualWire library will take care of all that Mike. OP needs to read the key, break it into 3 bytes, and send it out. VW will do the encoding, add some bytes to make sure the message has recognizable preamble at the receive end, etc.

I believe VirtualWire library will take care of all that Mike.

How will it know the format of his existing remote?

Sure VirtualWire will work if it has control over both ends but if he wants to use an existing remote then you are going to have to match the receiver to the remote.

Ah, I missed that subtlety - I thought he had control of both ends.

No, only one end.

I (perhaps, naively) thought that the rc-switch library would take care of the encoding/decoding.

...I got that impression from this:

I wire the reciever for my remote into the Arduino as per the diagram in the link, run the code, then steal the 24 bit key, or am I getting the wrong end of the stick?

Getting confused :wink:

Yeah, might work.

I wire the reciever for my remote into the Arduino as per the diagram in the link, run the code, then steal the 24 bit key, or am I getting the wrong end of the stick?

Yes but only if the receiver is doing all the same stuff as the remote you have. And also if the software running on the arduino knows about the protocol your remote is sending.

I see. I think.

So, the wireless plugs I have are using OOK (it seems to be a simpl 24 bit binary string), if my transmitter also uses OOK then it should work?

Had to look up the acrimony but it is one of the types of modulation I spoke off at first:-

So if both TX and RX use this form of modulation of the carrier then that is one of the compatibility boxes ticked.

Excellent, thank you.

The chipset in both my wireless door and my wireless plugs is OOK, so this is looking more probable.

I think for the few quid that the RX/TX modules are on ebay, I'll take a chance and have a mess around.

I did also find a chap who is selling a device that does just what I'm intending to make, for 35 Euros. I emailed him, and he makes them using an Arduino with RX/TX modules (that he linked me to on ebay - almost unbelievably, the very same ebay item I was already looking at), and using VirtualWiring, so I'll have a stab at making my own with this kit. If I fail, then for the sake of 30 odd quid I may buy one of his (although that really feels like cheating!)

how did this go? i just recently have started messing with my 433mhz things. were you able to get his source code? id be interested in that