Need help with understanding what component I need

Discussion in 'General Electronics Chat' started by sir dakka, Oct 3, 2013.

  1. sir dakka

    Thread Starter New Member

    Oct 3, 2013
    4
    0
    Hey guys, first post and I need just a little bit of help with my current project.

    This will be a wordy explanation of what I need so I hope I explain it well:

    Essentially I need to know what component/circuit I could use so that when a 5V pulse is sent through one circuit, a simple push switch is triggered for that pulse's duration in a completely independent circuit. In this way I can link two independant circuits and trigger one with the input from another with no electrical connectivity between them.

    I hope that makes sense, thanks for any input :)
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,792
    1,103
    Use an optoisolator.
     
  3. sir dakka

    Thread Starter New Member

    Oct 3, 2013
    4
    0
    Having briefly looked over what one of those is, is it simply and exercise in soldering the chip in place with pins 1 and 2 connected in the first circuit which I will be using to trigger the second, and complete the second circuit through pins 4 and 5, or do I need to know things about resistors and such.

    Bear in mind I'm a complete electronics noob and have no idea not to blow stuff up with mistaken ideas about circuits and such.
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    Optoisolators (optocouplers) use an LED inside..
    And LED always needs to be "fed" the proper amount of current. This is commonly done so with a resistor to set the current level the LED will see.

    There are thousands of posts on the internet on how to calculate the proper resistor value for an LED.
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,792
    1,103
    You will also need to tell us what the input voltage and current requirements are for the 'completely independent circuit', so that we can suggest how the optoisolator can drive it.
     
  6. sir dakka

    Thread Starter New Member

    Oct 3, 2013
    4
    0
    The second independant circuit is PICAXE-08M SERVO DRIVER (AXE024), (link : http://www.picaxe.com/docs/axe024.pdf)

    I am using pin 3 as a digital input pin, and want the opto-isolator to act as a switch so that when the pulse is sent to through the first circuit, the digital input to pin 3 is activated, i.e. as far as I can tell all that I require is that current flows through the gap in the circuit linking pin 3 to the 6V power supply and as such I just need to bridge this gap whenever current flows through the first circuit.

    Thanks again for your help, I feel like I'm getting somewhere at last :)
     
  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    do you really need isolation?
    any reason you don't just attach the 5V pulse wire directly to that input?
    are these 2 boards sharing a common powersupply?
     
  8. sir dakka

    Thread Starter New Member

    Oct 3, 2013
    4
    0
    They aren't sharing a common power supply, but I think I'll try connecting it directly and like you suggest as that's the simplest solution. I'll let you know how that turns out, thanks
     
  9. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    If they aren't sharing a common power supply its not a good idea I wouldn't think.. Opto is a better solution then.
     
  10. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,792
    1,103
    The opto-coupling would be something like this:-
     
Loading...