Sensor Questions

Discussion in 'The Projects Forum' started by franzschluter, Jun 13, 2009.

  1. franzschluter

    Thread Starter Active Member

    Jun 1, 2009
    Hi guys. I got questions regarding sensor and how to properly interface them since I am designing an interface card. I have a PLC unit (OMRON CP1L M40DT-D).

    Now the big question now is i've got these sensors..

    Hall Effect Switch -> I don't know if it is NPN or PNP? How do i determine this with a multimeter? There is no code written on it and is epoxy sealed. I tried to open up 1 unit to see the insides for code or manufacturer. No luck.

    I got three types of encoders.

    Type 1. RE-30 Dunker motor encoder. I downloaded their datasheet but to no avail what output is given? It simply says output via a photo transistor. But how do I determine if this is an open collector este a PNP or NPN type via a multi tester?

    Type 2. Hengstler Encoder.. I got 2 channels A and B. Are both NPN or PNP? Again same question how to test via a multimeter.

    Type 3. Hall Effect as limit switches... I got a bunch of them and burned a few guessing the polarity. This time I got it right..
    Pin config...
    pin 1 -> VCC
    pin 2 -> Gnd
    pin 3 -> Vout
    Same as above how to determine if its NPN or PNP type...

    Generally I know how to figure out a transistor if its PNP or NPN. But I am unsure with sensors. The manufacturer of dunker and hengstler never replies... And I need to know what configuration I should use (High or Low side). My plc does both but only has 1 common rail so in general an interface card is required. Switching speeds are very slow and low voltage.
  2. bertus


    Apr 5, 2008
  3. hgmjr

    Retired Moderator

    Jan 28, 2005
    What is the nature of your project? What exactly are you wanting to do?

  4. franzschluter

    Thread Starter Active Member

    Jun 1, 2009
    It's an automation project with PLC. I am trying to interface all the sensors to the inputs of the PLC. But the PLC unfortunately only has 1 common (COM). Turns out not all of my sensors are NPN some are PNP which is which I do not know. I have tested them out each. And since they are so many I forgot which is which.

    In any case since some are NPN and PNP this means that they will not be compatible with one another since I only got 1 COM. And we all know that PNP utilizes low side switching and NPN utilizes high side. Aside from these incompatibilities their working voltage and output voltage isn't enough to trigger the inputs of the PLC. I read 3.5V~4.3V on the output (So sometimes it triggers sometimes not). These are 5V devices and not always is the output really 5V. I am afraid of increasing the supply voltage and shorten its lifespan. Therefore I am making an interface card such that all outputs will be sinking.

    This can be simply done by using transistors. But to utilize pull ups or pull down will be a mistery for me unless I do trial and error which is dangerous for the components.

    The Hall Switches are inside the damn epoxy and when opened to peek inside the number is all blurred. So my only method on knowing if it's pnp or npn is trial and error.. It's indeed very hard to determine but I think it's not impossible. The thing is it has no base.. But maybe we could imagine the VCC as base? Or is this a wrong assumption? It goes "ON" with the magnet facing north pole.

    Also the encoders? Are they push pull? It is a dunker rotary encoder for motor. RE-30 model
  5. samuraimarc

    Active Member

    Mar 28, 2009
  6. franzschluter

    Thread Starter Active Member

    Jun 1, 2009
    That's the mystery.. There is no manufacturer for the magnetic switch...
    The sensors are for a slicing machine for making ham. Previously it ran with Micro controllers. But we found it too hard to troubleshoot and converted it to a PLC unit.
    Some industrial machines are top secret stuff. They had the pleasure of putting epoxy on the board so nobody will know what IC's are in it. LOL
    Last edited: Jun 14, 2009