Home› AMX User Forum› AMXForums Archive Threads› AMX Hardware

IO Port Output as 12V Trigger

sonnysonny Posts: 208
in AMX Hardware
Anyone ever used an IO Output as a 12V trigger, I've used these for inputs a number of times, but I'm out of relays on the processor and need a couple of outputs. If I read correctly, the pins are shorted to ground when the channel is turned on in the processor. When I turn on I can measure 12V between the output and the 12V connection, but when off I get 8V. I'm guessing this is due to it being a solid state output. The problem is when I plug into the Amp, the channel gets turned on, apparently reading this as an input??

Do I have to backend with a relay to make this work?

Thanks, Sonny

Comments

  • ericmedleyericmedley Posts: 4,177
    You can do this but I wouldn't. The IO Ports don't have a lot of power available. (I think less than 150 mA. Besides, wall wart power supplies are cheap. If you're needing more relays PM me and I'll point you in a good direction.
    E
  • shr00m-dewshr00m-dew Posts: 394
    Use them all the time in combination with an external relay. The Altronix break-aways are nice:

    http://www.altronix.com/index.php?pid=2&model_num=RB610

    Run 12v to the + side of the coil, and a wire from the IO output to the - side of the coil. You will then still have to hook up the NO/C/NC sides of the relay like you normally would.

    This keeps the IO's isolated and the power level safe.

    Kevin D.
  • AuserAuser Posts: 506
    shr00m-dew wrote: »
    Use them all the time in combination with an external relay.
    [...]
    This keeps the IO's isolated and the power level safe.

    A word of warning.

    I'm not sure what protection circuitry is inherent to the NetLinx IO ports, but if you plan on driving a relay coil directly from an open collector IO port such as on a NetLinx you should definitely have a reverse biased suppression diode across the relay coil. This removes the potential for voltage spikes generated when the coil magnetic field collapses when de-energised destroying the IO port.

    A quick Google search turned up : http://www.autoshop101.com/forms/hweb2.pdf. Page 12 explains why this is the case.

    Most pre-manufactured relay boards have a suppression diode or other protection circuitry built in and this may be true of the Altronix product linked to (the photo wasn't clear enough to tell). If you're not planning on using such a board - 5c part to save a $1000 unit? Priceless.
  • viningvining Posts: 4,368
    The altronix relay has the protection diode built in an is a great time saving device:

    Here's some dope on the IO and the relay.

    http://www.amxforums.com/showthread.php?1258-What-are-IO-ports-for&highlight=protection+diode
  • sonnysonny Posts: 208
    Thanks for all the info guys!! (or gals, just in case :)
Sign In or Register to comment.