Relay problem

Discussion in 'The Projects Forum' started by nathomas, Apr 18, 2011.

  1. nathomas

    Thread Starter Member

    Mar 3, 2011
    82
    0
    I have this relay circuit but it doesnt work the way i want it to. I have a Panasonic relay switch.

    http://datasheet.octopart.com/DK1A-12V-F-Panasonic-datasheet-148175.pdf

    It is a SPST/NO relay. I need to turn a cartridge heater ON/OFF with the relay. My circuit gives out 8V to switch the relay and it works fine. I check the connectivity of the relay, switchin it on and off and the connectivity breaks and connects accordingly. But when I take the AC supply and connect it with the heater, the whole circuit works as a NC circuit. So the cartridge heater works when there is no 8V going to the relay and stops working when the 8V is supplied. I have attached a very simple outline of the circuit I have.
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    I admit it - I'm stumped. Can you hear the contacts close when you apply AC? We are talking about the "single side stable" part, right, the one with just 4 pins?
     
  3. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Can you provide us with the exact part number of the relay that you are using so that we can confirm its operation with the specification that you have link to in your post?

    hgmjr
     
  4. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    How is the circuit being built? Is it a pcb, breadboard, or just wires on bare component?
     
  5. nathomas

    Thread Starter Member

    Mar 3, 2011
    82
    0
    Tha part number of the relay is DK1A 12V-F. The control signal for the relay comes from a breadboard but the relay circuit is just a couple of 18 gauge stranded wires. The thing I cannot understand is that now even if the relay is lifted from the bread board and the ac wires connected through the relay, power source and heater, the heater kicks in.
     
  6. nathomas

    Thread Starter Member

    Mar 3, 2011
    82
    0
    I did not try that. I am using the relay with a total of four pins. Two are the dc side and the other two are the AC side. Let me try and figure out when are the contacts closing when I apply the AC.
     
  7. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
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  8. nathomas

    Thread Starter Member

    Mar 3, 2011
    82
    0
    I understand that part, which is why i tried testing without any load. But atleast if it doesnt energize the circuit should be an open circuit. That is what I dont understand. Even without being energized the circuit is closed.
     
  9. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    If you have no power to the coil and yet the contacts are closed, then it's toast!
     
  10. nathomas

    Thread Starter Member

    Mar 3, 2011
    82
    0
    But it works without the AC side connected. So it shouldn't be dead right?
     
  11. mbxs3

    Active Member

    Oct 14, 2009
    141
    3
    Are the contacts stuck closed?
     
  12. nathomas

    Thread Starter Member

    Mar 3, 2011
    82
    0
    I tried the the circuit with another relay of 24V and it works fine. So I guess CDRIVE was right...
     
  13. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Most likely the contacts were probably subjected to an extreme over current condition, like a shorted component that it supplied current to. This, in turn fused the contacts together. Not that uncommon. ;)
     
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