How can I reduce the outputs with control method? MUX-DEMUXl, other?

Discussion in 'General Electronics Chat' started by Alberto Leandro Tupone, Jun 28, 2015.

  1. Alberto Leandro Tupone

    Thread Starter New Member

    Jun 21, 2015
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    Hi! I'm just looking for ideas in the better approach (is not a do-my-homework question), because my knowledge is poor, so any help will be preciated.
    I just finished my first circuit and because the size of the project, it has 15 connections between power-supply switch and the mainboard.
    The concept (this is not the circuit, just an analogy) is somethink like this:

    [​IMG]

    I'was looking for a way to convert this into a 3way (PWR, GND and CONTROL).
    I was looking in google for help about Radio Control, Infrared and even digital, but I'm afraid I'm very far away to understand those concepts without reading something about the introduction.
    So my question:
    It can be done this with an analogic basic electronic knowdledge? Some method sample? Keywords to google it? Any example to begin to learn?

    Thanks a lot in advance for your time to read this!
     
  2. Alberto Leandro Tupone

    Thread Starter New Member

    Jun 21, 2015
    18
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    I was reading also about "multiplexer" but I don't know if is a good approach
     
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    There are many different ways to reduce your rotary switch outputs to a single wire. First, let's make sure we understand the requirements.

    Your rotary switch is a 1-of-n selector, so only one output can be enabled at any time, correct?
    If this is true, then you can use an up/down counter and decoder to drive the relays, and have two pushbuttons and two control wires, one for up and one for down.

    For a bit more complexity but only one control wire, you can encode the two pushbuttons into two different pulse widths over a single wire, and decode them to drive the counter and decoder for the LEDs.

    Another way is to use a bar graph driver IC such as the LM3914. On the left side of your schematic, the rotary switch is replaced by a potentiometer, and the analog voltage from the wiper goes over a single control wire. On the right side, an LM3914 takes the varying analog voltage and decodes it to drive a series of LEDs. In dot mode, only one LED is on at a time. In the circuit on page 2, pin 9 should be left floating.

    www.ti.com/lit/ds/symlink/lm3914.pdf

    ak
     
    Last edited: Jun 29, 2015
  4. Alberto Leandro Tupone

    Thread Starter New Member

    Jun 21, 2015
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    Thanks ak, you are always a good teacher! Actually I messed up, you are right, my analogy is wrong because switchs can be enabled at any time. Actually the real switch module is this:

    [​IMG]
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,542
    1,251
    If this is in a relatively low noise environment, this still could be done with a single analog signal. Run the 8 switch lines into a D/A converter, send the analog output to the receiver, use an A/D converter to recreate the digital bit pattern. Even though you have only 8 digital signals, I recommend 12-bit devices so their internal linearity errors are less than the resolution you need.

    As a minimal digital approach, you can use a UART (Universal Asynchronous Receiver Transmitter) one each end of what would now be a single digital serial line. Older UARTs like the AY-3-1015 are in a 40-pin package. Large, but all control functions are brought out to individual pins, so you don't need a microcontroller to set it up for operation.

    And any small microcontroller can do this if you can handle the programming.

    ak
     
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