how do I interface a 5V sourcing signal with a 12V sourcing signal?

Discussion in 'General Electronics Chat' started by strantor, Nov 29, 2011.

  1. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
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    I am trying to install a laser micrometer. it measures the diameter of a wire as the wire passes through it, and records if/when the wire goes out of tolerance (too large/too small). The micrometer needs a footage pulse input for this. This is usually accomplished by installing a rotary reed switch between terminals 8 & 9. The reed switch will pull the 5V terminal 8 LOW (draws 10mA when closed) and the laser micrometer registers this as a pulse. There is no reed switch currently in place and I am trying to avoid adding one by using an already in-place 12V encoder signal. The encoder signal currently goes to a footage counter mouned right next to the micrometer so logistically it's easier. I can't figure out how to do it. I tried using a transistor but it didn't work. please have a look:
    [​IMG]


    The thing in the top right is an exploded view of the encoder, which is shown in the top left terminated at the existing counter. White & green correspond to Data A & B. Black & red correspond to +VDC & common. Black lines correspond to what's already in place, and blue lines correspond to my addition.

    transistor is 2N3416
     
  2. thatoneguy

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    Feb 19, 2009
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    Optoisolators on both if they can source enough current.
     
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  3. strantor

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    Oct 3, 2010
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    I just rummaged through all the crap I have here and my only opto is a MOC3021 Triac.

    I just tried basically the same thing as my original plan with the transistor, only this time with a IRFD113 mosfet and no voltage divider, and that didn't work either; I was sure it would.
     
  4. t_n_k

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    Mar 6, 2009
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    Are you looking for the low-high transition on Data B or vice-versa?

    What are the logic/input settings for input B config switches on the PLC?

    Do you have a means of checking the voltage levels - say with a CRO...?

    Also any limitations / requirements for the minimum on-time duration at the laser micrometer control? What's the encoder output pulse width?
     
    Last edited: Nov 30, 2011
  5. strantor

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    Oct 3, 2010
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    either rising edge or falling edge, doesn't really matter. signal can be inverted.
    The dip switches are factory default, just the way they're shown in the graphic.
    yes, I have a fluke scopemeter and a multimeter
    That remains to be seen. Everywhere I have seen these laser micrometers set up, the rotary reed switches give them 1 pulse per foot. If I can get the encoder input to work, it will be recieving 100 pulses per foot. The laser mic has a feature to scale the pulses, but I'm not sure what its limitations are.

    Well, I guess the pulse width would depend on the speed. its just a square wave.

    BTW to save you some time, if you are going to come up with a big circuit, I wouldn't. I plan to get an optoisolator tomorrow (unless you see a reason why that wouldn't work) - but I was just trying to make sure there wasn't an obvious immediate solution that I was somehow overlooking.

    Thanks
     
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