Switch (close contact) ativated on 0v and deactivaed on 5v

Discussion in 'General Electronics Chat' started by ricardorio, Apr 26, 2017.

  1. ricardorio

    Thread Starter New Member

    Apr 26, 2017
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    Hi,

    I don't have much experience with electrical circuits, but now I'm facing an issue that google was not able to help (or me not able to understant) so I hope someone could at least point me in the right direction.

    I have circuit that in order to be activated I only have close the circuit image in attachment (Router circuit.png).

    The circuit responsable to activate/deativate this switch delivers 5v when it should open the router switch and 0v when it should activate/close router switch the circuit.

    I have investigated the opto-coupler in order to isolate both circuits but I was unable to find one that closes the curcuit when the input is 0v and opens when 5v is present. I don't know if I'm even on the right path.

    Hope this was clear, and I'm sorry if it wasen't more descritive or into details, but I can try to give more details if needed.

    Any help is welcome.

    Thanks in advance,
    Ricardo Rio.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    18,455
    5,675
    If you want an inversion, just use the emitter output in place of the collector.
    Max.
     
  3. ricardorio

    Thread Starter New Member

    Apr 26, 2017
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    Hi Max,

    Thanks for the quick response, so you think I'm on the right track and I can use an opto-coupler?

    Just didn't understand the inversion, should I switch on the router (image in attachment) on the 5v, 0v side?

    Regards,
    Ricardo Rio.
     
  4. Reloadron

    Distinguished Member

    Jan 15, 2015
    4,301
    2,085
    Any reason you can't just use a SPDT (Single Pole Double Throw) relay having a 5 Volt coil? Unless each 3.3 volt supply is isolated in the drawing what is the reason for the opto coupler? Maybe I am just not understanding.

    Ron
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    18,455
    5,675
    An inversion is place the resistor and output in the emitter of the opto rather than the collector side.
    Max.
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
    7,983
    6,781

    To elaborate on Max's solution, swap the optocoupler output and the 10k pull-up resistor. That is, connect the "c" (collector) of optocoupler to +3.3V, connect "e" (emitter) to a 10k resistor and the other end of resistor to ground. Your output is at "e" of the optocoupler.
     
  7. ricardorio

    Thread Starter New Member

    Apr 26, 2017
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    https://www.broadcom.com/products/o...l-plastic/other/phototransistor/hcpl-817-000eHi,

    Ron, it has to be triggered by the tension variation I don't have control on left and right circuit I want to integrate both circuits, on the left I have pannel that controls a router (right circuit), when they click on a button to activate that router ouput the output goes from 5v to 0v, and I can't change this behaviour, so the SPDT for what I read is a manual switch correct?

    Max and GopherT, I have elaborated a little better the left circuit (image in attachmnet) in order to try to explain myself a little better, I do not have access or controll to the left or right circuits, I need the integrate both, from the left side I have 2 wires that when we want to activate the router right circuit switch have a potêncial diffrence of 0v and when we want to deactivate the right circuit switch we have a potêncial difference of 5v. On the right circuit also I have to wires that have a difference in potencial os 2v that when we close the circuit it activates the router as expected.

    So I need something in between the when receives 0v from the left it closes the contact/switch on the right circuit and when we have 5v on the left circuit it closes the switch on the right circuit.

    I was searching and came across an Optocoupler HCPL-817 in this link: https://www.broadcom.com/products/o...l-plastic/other/phototransistor/hcpl-817-000e I don't know if this should do the trick and how to connect or if there is a better way.

    Thanks again for the time and patiece.

    Regards,
    Ricardo Rio. Router circuit integration.png
     
  8. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    Your drawing is correct then, a Zero voltage on the left will give a Zero voltage on the right, and vice-versa.
     
  9. ricardorio

    Thread Starter New Member

    Apr 26, 2017
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    Hi Dodgydave,

    So this Optocoupler HCPL-817 in between the 2 circuits will do the trick correct?

    Best regards,
    Ricardo Rio.
     
  10. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    8,151
    1,412
    Yes, it will give you the result you need.

    Another common opto-coupler is a 4N35
     
    Last edited: Apr 27, 2017
  11. ricardorio

    Thread Starter New Member

    Apr 26, 2017
    5
    0
    Hi all,

    Thanks, I will test this and will give you feedback.

    Best regards,
    Ricardo Rio
     
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