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Low voltage relay question

Discussion in 'Electronic Basics' started by John Popelish, Mar 16, 2007.

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  1. If your current values for your loads includes the initial
    inrush, then I think you'll be fine. But I am worried that
    the strobe light includes a big capacitor that will suck
    lots of current for a few milliseconds, right while those
    contacts are bouncing to a stop, and that will eat the
    contacts. I think I would look for a 3 to 5 amp contact
    rated relay. That are pretty common. Or drive two of these
    in parallel and use one for the horn and one for the strobe.
     
  2. AB

    AB Guest

    Still a newbie so please bear with me....

    I have this 12VDC alarm panel that limits the siren output draw to
    110mA. As this is not adequate for me, I replaced the siren with a
    beefier model that draws 750mA and added a small strobe light that
    draws 150 mA...so 900mA total draw.

    I rigged a small relay to separate the alarm circuit from the new
    siren/strobe...this one here:

    http://www.radioshack.com/product/i...=12vdc+relay&kw=12vdc+relay&parentPage=search

    I also got a 1000mA rated wall wart to power the new setup. My
    question is that since I'm pretty close to the maximum draw rating of
    both the power supply and the relay...will the relay get hot and burn?
    The circuit will only be in use for 12 minutes maximum and then the
    alarm panel resets, but I really can't run the siren for 12 minutes to
    test it.

    What do you all think, should I be OK with this setup for intermittant
    use?
     
  3. AB

    AB Guest

    Are we talking just a ruined relay here or a possible fire risk?
     
  4. No fire. Just the possibility of a welded contact that
    won't release.
     
  5. Chris

    Chris Guest

    Mr. Popelish has been steering you in the right direction. Since
    you're at Radio Shack, try their 12VDC 10A DPDT relay Model: 275-217
    with socket Model: 275-220. This will do the job -- it will reliably
    work for you.

    Good luck
    Chris
     
  6. I think that is the part number for a relay socket. I think
    the 10 amp relay with 30 mA coil current is 275-248.
     
  7. ehsjr

    ehsjr Guest

    You're right 275-248 is the relay he should use.

    Ed
     
  8. AB

    AB Guest

    Thank everyone for (once again) great advice. I couldn't have done any
    of this before hanging out here.
    Bob
     
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