HELP ME TO BUILD THIS CIRCUIT

Discussion in 'The Projects Forum' started by ORGENES, Feb 7, 2016.

  1. ORGENES

    Thread Starter New Member

    Feb 3, 2016
    9
    1
    Hi everyone...
    I want to design a system which take signal from keyboard to the micro controller then to the RF transmitter. RF transmitter transmit signal to the RF receiver then to the micro controller and signal as message to be displayed on display LCD. Help me idea to design that circuit and additional electronics components to make circuit stable on operation
     
  2. szabikka

    Member

    Sep 3, 2014
    77
    1
    Hi ORGENES!

    If I get it right you have a computer keyboard that you have connected to a microcontoller and you have another microcontroller driving an lcd and you want them to communicate via an RF transmitter-receiver system. I presume you have written the programme for the microcontrollers and you need help with the radio frequency communication part.

    First of all, try to find an RF receiver and RF transmitter module. These are rather common and inexpensive nowadays. Personally I prefer the 433 Mhz ones, but there are others available too. For example, here are some: http://www.hoperf.co.uk/shop/HopeRF.html . Be careful to choose same modulation type receiver as your transmitter, for example, for an ASK transmitter choose an ASK receiver, etc. After that you need an encoder IC that is connected to your transmitter and a decoder IC that is connected to your receiver. These are needed because if you don't encode/decode the info you want to communicate than your receiver will pick up every nearby transmitter's communicated data and will go crazy. Typical encoder/decoder IC pairs are: HT12A/E and HT12D/F or PT2262 and PT2272. Refer to the corresponding datasheets to know which one is which and to familiarize the pinout. As these ICs can only encode/decode 4 bit data and a keyboard produces 8 bit or 11 bit data strings (depending on keyboard type) you will need a multiplexer on the transmitter side and a demultiplexer on the receiver side.
     
  3. ORGENES

    Thread Starter New Member

    Feb 3, 2016
    9
    1
    Thanks szabikka...

    I get you right, if i will use PIC micro controllers which these have the pots for Analogue to Digital converter (ADC/DAC) so there is no any need of RF encoder and Decoder?, what can you say about that brother?

    Also according to that mentioned components in your reply, the circuit already complete or there are some small components such as passive or active components for circuit to work good?

    Also can you give a simple circuit diagram for me to gain more knowledge about that?
     
  4. szabikka

    Member

    Sep 3, 2014
    77
    1
    The keyboard, PIC, mux/demux, encoder/decoder and LCD part of the circuit is completely digital, so there is no need for ADC/DAC converting. The only analogue part here is in the transmitter/receiver circuits amplifier part, but that is already built on the RF modules, so you don't need to build it yourself. I think that throwing in any kind of ADC/DAC converting just makes the circuit more complex and hence, difficult to build and those extra parts just consume excess power.

    If you decide to build the circuit according to my suggestions, you will need some passive components. For example, the encoder/decoder ICs contain an oscillator, that needs either just a resistor to connect between OSC1 and OSC2 pins (in case of HT12D/E/F), or needs a quartz crystal, two capacitors and a resistor (in case of HT12A). Refer to the datasheets to know which pin is which and how to place these components. For the one resistor oscillator ICs bare in mind, that the frequencies must be as such:
    fosc (HT12D/HT12F decoder) = 50 fosc (HT12E encoder)
    fosc (HT12D/HT12F decoder) = 1/3 fosc (HT12A encoder)

    I took a look around on the web to help you with circuits and found these circuits. There is lots of detailed info in both. It's worth to read them, but don't copy the circuits as they are a bit different than the one you need.

    http://www.electroschematics.com/8712/rf-based-wireless-remote-control-system/
    http://www.circuitstoday.com/remote-control-circuit-through-rf-without-microcontroller
     
  5. ORGENES

    Thread Starter New Member

    Feb 3, 2016
    9
    1
    Okey , i get you right my brother szabikka, now let me design that circuit and to stimulate it in Proteus, i will inform you the progressive of the task.

    Thanks
     
    szabikka likes this.
  6. szabikka

    Member

    Sep 3, 2014
    77
    1
    Okay, I 'm looking forward to hear the results.
    Good luck!
     
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