Easiest way to send / receive a 1 and 0 wirelessly?

Discussion in 'General Electronics Chat' started by fender7802, Jun 25, 2014.

  1. fender7802

    Thread Starter Member

    Apr 7, 2012
    43
    0
    Hi all,

    I'm looking for a simple way to wirelessly transmit either a 1 or a 0. I want to flip a switch which sends say 2.5V to a transmitter. Then the receiver goes to 2.5V (or any 'high' value). Then one I flip the switch to 0V on the transmitter, and the receiver goes to 0V (or any 'low' value).

    I don't need a far range. 10 feet would be the maximum. I am a bit concerned about noise and interference. This is where I kind of get lost. Because I don't want noise to give the receiver a false reading, does that mean I need to worry about encoding and decoding?

    Is there such a thing as a simple transmitter and receiver like I'm describing or is it more complex involving encoding and decoding? Is there a product someone can point to?

    Thanks for the help!
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,565
    2,379
    In the past I have used RWS-434 & TWS-424 RX/TX and HT-12D/12E encoder/decoder, but there may be more modern alternatives now.
    Max.
     
  3. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    Yes, some wireless xcvrs send an RF pulse for one state and no RF for the other.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,153
    3,059
    Do you need RF? Just use a TV remote (an IR transmitter-receiver pair). No carrier signal is "off", presence of the carrier signal is "on". The high frequency carrier allows much greater sensitivity, by eliminating noise at other frequencies. For just 10 ft, you may get away without modulation if you take care with the "optics" - shading the receiver and making sure the transmitter is pointing at the receiver.
     
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    There are thousands of "remote controlled relays" on ebay,etc... that will do exactly what you want.

    why don't you provide some more details on what needs to happen or what is being triggered by this high/low signal.

    is it life or death if you get a false reading or just an "oops"
     
  6. fender7802

    Thread Starter Member

    Apr 7, 2012
    43
    0
    Thanks for the replies. A remote controlled relay actually sounds like what I'm trying to accomplish.

    What I want to do is, when the transmitter gets its high signal, the receiver should turn a relay on. When the transmitter gets a low signal, turn the relay off.

    I need to mention that this is a project for school so I can't exactly just buy the thing off ebay. I was hoping to find just the transmitter and receiver (one that is encoded is a bonus) and then hook up my own relay, design a pcb, make a project case, etc.

    Now I have the relay I planned on using, it is rated for 16A. I don't think IR would work because the transmitter won't have a line of sight to the receiver. I'm thinking RF is the best choice.

    It's not the worst thing in the world if I get a false reading. It would be preferred not to, but I'm on a fairly tight deadline if that means learning encoding / decoding, I'd opt for an occasional false reading.

    So a simple transmitter / receiver that can distinguish a 1 and 0 is still what I need, and if it has noise immunity, great.

    Thanks for the help guys, it's much appreciated.
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,067
    3,837
    Where in the world are you located and, nobody was suggesting you buy a finished project off eBay, but really cheap transmitter receiver pairs are available there ($5 with shipping from china- 4 weeks).

    Other options are possible - even building your own.

    EDIT: I was wrong, some will arrive to US locations in 3-5 days
    eBay
     
    Last edited: Jun 25, 2014
  8. fender7802

    Thread Starter Member

    Apr 7, 2012
    43
    0
    MaxHeadRoom, I've been looking at the datasheet of the chips you posted. If I use the transmitter and receiver each with the 4-bit encoder and decoder, do I still need a microcontroller with software to use the chips? It looks like I could just put my 2.5V and 0V into the D1 pin on the encoder, then attach DOUT to the transmit in pin, and just copy what they have for the receiver. Am I missing something? My data is not UART or serial or anything like that just two plain voltage values.

    Edit:

    GopherT, thanks for the response. I'm located in Boston, MA. I would like to use something like what you posted. My only concern is: can I use this pair with just plain analog voltages and not serial data? Also, if I wanted to add an encoder/decoder to it, would that mean I need software or do the chips do all the encoding/decoding? I am wondering if this whole process can be done without a microcontroller. Most all of the tutorials I've read on using RF transmitters/receivers like this are written for use with two arduinos.
     
    Last edited: Jun 25, 2014
  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,067
    3,837
    Yes, it is just a transmitter and you can send any analog signal. Transmitted 'digital' signals are usually some type of shift key encoding of an analog signal - one frequency may represent a 0 and another represents 1. These cheap transmitters can handle up to about 5kHz sine wave. I was using an audio tone generator and transmitting to the receiver. The one I bought would transmit about 30 feet and would handle about a 5kHz tone. I think it is mostly limited by the op amp - I haven't taken time to determine if the filter design on is cutting off higher frequencies or if the op amp is band width limited.

    Anyhow, send a 400 hz test tone to align the antennae and make sure you can hear that on the receiver. Then, you can turn on or off the audible tone to make your 1 or 0.
     
  10. fender7802

    Thread Starter Member

    Apr 7, 2012
    43
    0
    Thanks for your help, GopherT. I'm going to order a pair now.
     
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,067
    3,837
    I you have a deadline, start early and stick to it. These are temperamental and getting the frequencies to align (playing with coil slightly and antennae) can be a bit of trial and error (or art). Also, you may get the frequencies matched but range is not assured.

    Good luck
     
  12. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    Sounds like a good idea :)
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,565
    2,379
    You just set up to a 4 bit pattern on the encoder and if you wish you can set an address on the data lines, and just use a push button to transmit the bit pattern.
    Set the decoder to the same address and you get the same bit pattern out of the 4 outputs, a relay can be attached to one or more of them.
    You do not need a micro of any kind.
    Max.
     
    Last edited: Jun 25, 2014
  14. ErnieHorning

    Member

    Apr 17, 2014
    67
    17
    I’m late to the party but if you just want a simple on/off and you’re not concerned with any data streams, just buy a wireless doorbell. They’re less than 10$ and go about 50 feet or so. Hack the speaker output. I just built one a few months ago using a latching relay that toggles on/off.
     
    wayneh likes this.
  15. fender7802

    Thread Starter Member

    Apr 7, 2012
    43
    0
    Thanks again for all the help, guys. Lots of good ideas.
     
Loading...