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intrinsically safe safety 12v

Discussion in 'Electronic Design' started by HarryHydro, Feb 15, 2007.

  1. HarryHydro

    HarryHydro Guest

    Hi Folks:
    I'm hunting for a solution to this problem. I have a 13.2V battery
    (charging) in a safe area. This goes through a custom barrier (ISCOM)
    to a computer in a hazardous area. There is a new intrinsically safe
    solenoid in the hazardous area, but it needs about 10V at 30mA to
    switch. The added current would blow the ISCOM, which already doesn't
    have the voltage the solenoid needs. The common zener-resistor
    barriers I've seen drop too much voltage and we have no 24V that the
    active devices require. The best we've come up with so far is 9.6V
    that works when the solenoid is warm, but not cold (like today). This
    is taking into account the voltage drop in all the wiring as well.
    Any ideas apprecieated!
    Thanks!
    Harry
     
  2. Phil Hobbs

    Phil Hobbs Guest

    When you say "hazardous area", I assume you mean one that may have an
    explosive atmosphere, is that right? And in an industrial setting?

    Could you tell us a bit more about the exact requirement?

    Cheers,

    Phil Hobbs
     
  3. Can't you use a pneumatic actuator? Or a mechanical link?
     
  4. Guest

    An I.S. DC-DC barrier would be preferable to the somewhat dated Zener
    blocks. The input supply voltage feeds 1:1 to the load but is
    galvanically isolated and I.S. approved

    Pepperl+Fuchs do a whole range of I.S. isolators. Google instantly
    turned up ...
    http://www.247able.com/mcp/Barriers_Isolators.html
    look at the kFD2 solenoid driver range.
    Expensive naturally.
    john
     
  5. nospam

    nospam Guest

    So hang a small dc-dc converter across the battery to get enough voltage to
    drive through a conventional barrier?

    --
     
  6. HarryHydro

    HarryHydro Guest

    Hi: Thanks for the reply. In the safe area we have a 12V battery bank
    and charger. There is a custom barrier box for a computer that reside
    in the hazardous area. There are pneumatic operators here also . In
    an effort to save time and money (hard conduit, etc.), we're using an
    intrinsically safe solenoid set. These solenoids need 10V @ 30mA to
    switch. The computer provides an open-drain FET for switching. This
    may be 12V only, being clamped to the + rail. What we've done is use
    another custom barrier for the solenoid, but I think these are
    expensive to. Overall, it's still cheaper than re-tubing.
     
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