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Posts posted by sigmacom

  1. DTMF, huh? Good and cheap solution, but too "classic analog" don't you think? I prefer digital; it's more secure...
    Anyway, I think it's perfect for our friend with the level of knowledge he has.

    Tips for james120479:
    - You can ommit the flip-flops (4013) if you don't want to hold the last state (which transmitter was last used).
    - Forget the 418 MHz receivers we discussed earlier. You must use a simple FM radio receiver instead.

  2. What does Solid State mean in your mind?
    Solid State in my mind means not mechanical

    I agree with this: "Solid State in my mind means not mechanical" but the schematic, can't be called "a solid state relay":

    As you know, relays offer isolation between the relay contacts and the coil. Also, you can control (on-off) any kind of voltages/currents, with indepedent voltage on coil.
    A solid state relay (the component, not substitutes) does all this, because it has a diode as coil, and photosensitive thyristors/triacs as relay contacts (for example, with 5VDC as control voltage, you can do 220VAC on-off control).
    None of the above conditions met by the schematic posted above, so I couldn't call it "a solid state relay". Anyway, it does it's job! ;)
  3. A very simple approach, is shown in the following schematic.
    The 2 resistors of 1 kOhm each, make a voltage divider /2, providing a Vcc/2 voltage to the (+) pin of the comparator. This is used to set the (+) input at higher voltage vs the (-) input -and so- force the output (Y) to high state (Vcc).
    When voltage at pin (-) of comparator goes more than Vcc/2, then the output of the comparator (Y) goes at low state (GND) and vice versa. If you ommit the resistors, the input voltage at pin (-) must be > Vcc to trigger the output.

    Try it! :D


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