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switching between two outputs

Discussion in 'General Electronics Discussion' started by mingas, Mar 22, 2015.

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  1. mingas


    Mar 22, 2015
    Hi guys, I would really appreciate if someone could give me advice on how to build circuit for this case. On my circuit input I have slowly arising voltage from 0V to 10V, and on my circuit I have 2 outputs. When input has 0V-5V, first output has to be active, but when voltage rises from 5V-10V, first output has to deactivate and second output become active. And vice versa, when voltage decreasing to less than 5V, second output has to deactivate and first become active.

    5V is the point where output changes, depending on voltage.

    I was thinking to use 5V or 6V relay which gets active when voltage gets close to 5V. But relay coil will always use energy, which is not good in my case, as I need as much as possible voltage and current on outputs. Can you help to project switching between two outputs using transistors or comparators circuit? Thanks in advance.
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Welcome to electronicspoint.

    A comparator is the right circuit to detect the threshold (5V) and create a signal that switches between two outputs. The switch itself is another story. What currrents are involved, what is your frequency range? How much voltage drop across a "switch" can you tolerate?
  3. mingas


    Mar 22, 2015
    Thanks for your quick reply. To make it more clear I have drawn a plan of my circuit and hosted this picture here:
    I am using around 500mA-800mA on main input, and I need to have voltage drop across a switch as small as possible.
    In my circuit I use power step up booster, because on main output I need reach 5V as quick as possible, but when voltage reached more than 5V on main input, I need to switch from step up booster direct to main output, otherwise I will damage my power step up booster. I am not very strong in electronics, its still not clear for me how to use comparator, as my voltage rising from 0V to 10V on main input. so how can I compare my voltage on comparator if, for example, on main input will be 0,5V? I would really appreciate if you would draw a quick plan to explain. Thank you very much in advance.
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    I would just power the boost converter from the 0 to 10v rail. When the input is greater than the set output voltage the output voltage will rise. The losses should be less than the diodes you have.

    The one important consideration is that the regulator itself can be safely powered from the higher voltage rail.
  5. mingas


    Mar 22, 2015
    I have tried to connect boost converter from 0V to 10V, but I have damaged couple of them. When voltage rises over 5V on boost converter input, on output I have the same voltage, but then boost converter doesn't work when input less than 5V, input and output remain the same (1-1V, 2-2V, etc) Something damages in boost converter after this.
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