Simple RF Transmitter/Receiver?

Discussion in 'The Projects Forum' started by yugi4542, Mar 13, 2014.

  1. yugi4542

    Thread Starter New Member

    Jan 30, 2014
    4
    1
    So I'm relatively new to electronics and I'm slowly working my knowledge base up. I had an idea for a project, but I don't know where to find the resources to help me figure out what to do or what components I need.

    I'm a waiter, and I want to create a small on-off switch that I can hand to one of my tables. When the switch is flipped, a radio transmitter would be activated inside, which would broadcast to the matching receiver on my wrist, turning an LED on (so that I am now aware that my table needs me).

    I can have up to three tables at one time, so I'll be using three separate transmitters to light up three LEDs that are independent of each other. I'm fairly confident that once I can get one transmitter/receiver combination working, I should be able to get all three working on different frequencies, and from there I should be able to make the final circuits.

    I know my way around basic circuits, but I'm totally new to radio signals. If anyone has any pointers on where to start on this or can tell me what ICs I should be looking at, I would greatly appreciate it! I've been Googling and searching this forum for three hours and everything I find is either *way* too complex for my application, or uses paper cups with wires wrapped around them. I need something simple, but precise so I can rely on it.

    Thank you! :D I look forward to getting to know all of you as I get better at this!

    {TL;DR: I need to build three radio transmitters, and one receiver that can receive a single-tone signal from each of the three transmitters.}
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,145
    3,056
    You might look at one of those things that can locate your keys or the TV remote by pushing a button. It's a one-to-many model, whereas you needs many-to-one, but maybe a place to start. Unless you really want to get into radio as a hobby, I'd look long and hard for an off-the-shelf solution. The clever folks here can likely help you locate the best solution.
     
  3. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Might be a start.
    Need 4.
    Disable 3 buttons on each transmitter.
    Use one receiver with latches.
    Scr I'm thinking. To drive leds.
    quote
    "There are four buttons on the remote control, and respectively correspond to the four data bits to the receiving board output pin D0, D1, D2, and D3 of. Press the buttons transmit signals, the corresponding data bit is output high.

    Module function description:
    This module contains no self-locking function, simple implementation, wireless remote control by pressing a key, the receiver output a high level, the corresponding output when key releases. High level at the receiving end disappear, and each channel are independent of each other, each other. The output of high level can directly drive the relay, as shown in the shop
    VT foot is receiving signal terminal. There is no detailed information
    Module's work
    Button. The corresponding relationship between The output of The receiver pins:
    A - - > D2
    B - > D0
    C - > D3"
     
  4. yugi4542

    Thread Starter New Member

    Jan 30, 2014
    4
    1
    Wayneh and inwo, thanks so much for your responses! Alas, I was hoping to use this project as a springboard into RF transmitting, as I have a few ideas rolling around my head that will require that knowledge in the near future. (I also want the satisfaction of building the thing myself, to be honest ;) )
     
  5. atferrari

    AAC Fanatic!

    Jan 6, 2004
    2,648
    764
    I've seen that implemented but fixed to the table. As you surely know, people is attracted and tempted to bring this or that home. Even the menu.

    I learnt that when asking why the small thing used to ground black pepper at the table was son high (around 80 cm); to avoid people stealing them.
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,145
    3,056
    Ah, well that's a very different situation then.
    I've seen some links offered here to very nice RF modules. Sorry I can't recall where. But these are pre-made RF modules that free you from actually building a radio - which can be challenging without the right tools, like an oscilloscope - and let you focus on the functionality of the rest of the device. Maybe go take a look at Sparkfun.
     
  7. sirch2

    Well-Known Member

    Jan 21, 2013
    1,008
    351
    You need to be a bit careful, even with bought modules, I bought some cheap ones off ebay and when they were running my car key would not work, even though the modules were about 30 feet away.

    I understand that you want to build your own but to answer wayneh, here's a couple of good sources:

    http://shop.ciseco.co.uk/rf-module-range/

    http://www.rfsolutions.co.uk/
     
  8. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Welcome to AAC.

    RF is not for the lighthearted. It is almost equal parts art and science. This is not to deter you in the least, but just know this is not a subject you can jump into immediately.

    That said, if you really want to learn RF and electronics, look into the American Radio Relay League or grab an ARRL handbook. This will help get you started.

    If, however, you need something immediate, take a look at Linx Technologies. They have an assortment of RF modules (to be added to other electronics to do what you want) as well as finished products. This is one place to go for a robust and reliable RF solution. There are others I'm sure, this is just the one I've come across in the past.

    I have several of the modules inwo referenced. I haven't had a chance to do any distance tests yet, but you won't beat the price even if you were to build one yourself. Keep in mind you'll still have plenty to do with an RF module such as figuring out how to take the incoming signal and make it useful. If it were me, I think I'd put the receiver into a pager-like case and program a microcontroller to trigger a pager motor in short bursts when any of the three signals are received and light up a specific colored LED for each signal. Then add a push button to acknowledge the signal and shut the motor and LED off.

    Sounds like a fun project however you decide to tackle it.
     
  9. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    sirch2, the modules were probably on 433.9 mhz. thats the normal key frequency. a few years ago, the navy started using a new radar system in california, peoples key fobs wouldnt work for miles around.
     
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