RFID NC, Bell NO :/

Discussion in 'The Projects Forum' started by shezza, Mar 19, 2014.

  1. shezza

    Thread Starter Member

    Mar 19, 2014
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    Hi all,

    I purchased a new bell recently and seperately I also purchased and RFID scanner to operate the electronic door strike as well.
    I learnt today that my RFID scanner works on a NC system while my bell works on a NO system. Great learning lesson!
    So I had a thought on how to tackle this and wanted some thoughts/feedback.


    Firstly I will need to purchase a NC electric door strike. And for the more complicated part, basically; Im thinking of connecting the RFID scanners power to the lock, through a relay which is NC, when the relay is magnetised by the bell lock control, it opens the circuit and opens the lock.
    Sound about right?

    Thanks
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    What is the model of Rfid sensor, if i am understanding you, your Rfid has a set of NC contacts and these will open when a valid Rfid device is present. If that is the case you will need to use an external slave relay with a set of change over contacts to feed the bell.

    OR if you can get inside of the Rfid sensor and replace the relay with a change over type.
     
  3. shezza

    Thread Starter Member

    Mar 19, 2014
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    You understand correctly. I was thinking of a change over relay, but to have the change over controlled by the power coming from the "lock open" button on the bell to make it an open circuit to open the lock. Im not exactly sure what you mean...
    I have the Sebury K4. Im thinking there must be a way to choose between NC and NO, but dont see it...
    I have found it in a kit where you can choose the door strike type (NC or NO), so the supply can help me out. Though maybe not with the bell. Its all quite confusing to me!
    http://www.ebay.com/itm/12V-3A-Door...661?pt=LH_DefaultDomain_0&hash=item4d1a6959bd
     
    Last edited: Mar 19, 2014
  4. shezza

    Thread Starter Member

    Mar 19, 2014
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    Ontop of all that, my continuous research has come up with another manual for this device with information suggesting it can work a NO door strike. How its done? Cant for the life of me work it out! Plus wiring a one way diode across the positive to the negative... How does that work?! I opened it up and didnt find any adjustments inside sadly. And yes, I did wire up the "Blue" wire to work as NO but it still operated it as NC.
    If anyone could make better sense of it, would really appreciate it!
    http://www.ssc.ro/manuale/cititor-stand-alone-interior-sebury-cartele-proximitate-cod-controller.pdf
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,364
    Most control systems are designed to be used as either NO or NC.

    To use NO contacts, connect your device to NO and COM.

    To use NC contacts, connect your device to NC and COM.

    This sounds too obvious and hence there is something else that is preventing your setup from functioning as desired.

    Perhaps your device needs to be powered from an external power source. In that case, connect power to NO, COM to device, device return to power.
     
  6. shezza

    Thread Starter Member

    Mar 19, 2014
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    0
    So my findings are as follows...

    So NC is constant + and NO is constant -. Everything is closed... no open circuits happening.
    Mind is boggled! :confused:
    Im now thinking of using a changeover relay to move on from this madness and have 87 connected to the lock while 87a goes to nothing. Hope that makes sense! Do I need a special relay though that can handle being constantly energised? I forgot to check the A draw, but I expect it to be very minimal.
     
    Last edited: Mar 20, 2014
  7. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
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    looking at your picture device, it has a set of voltage free change over contacts, so you need to use the NO and COM terminals, feed the lock supply through these, so when a valid Rfid device is detected, the contacts will close and make the lock work,


    OR use the NC and COM to revmove power from the lock.
     
    Last edited: Mar 20, 2014
  8. shezza

    Thread Starter Member

    Mar 19, 2014
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    You would think they were voltage free, but they arent :/ They are voltage full! Even the earth contact is constant... Me no understand :confused:
     
  9. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
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    Ok so use the NC and Com, put the lock posative to +12,connect the lock negative to NC, the lock should be powered up now, when a valid device is detected the power to the lock will be removed.look at page 6 of the manual, blue or orange wires.
     
  10. shezza

    Thread Starter Member

    Mar 19, 2014
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    That is the one way I can get it to work. Being I have a NO door strike, it operates it in reverse and will only lack when I scan a valid chip.
    I can get a NC strike, but then I run into the trouble of the bell needing the NO strike.
    I wish it was so easy :p
     
  11. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Do you have a lock that needs power to lock it, or needs power to unlock it.

    The unit you have has a set of voltage free contacts (see page 5 of manual,) purple, blue, orange wires are the relay, so you can wire it your own way.
     
  12. shezza

    Thread Starter Member

    Mar 19, 2014
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    It needs power to unlock it. All the contacts are showing voltage though and then removes it when I apply a working RFID tag. This is why Im going a bit crazy :)
     
  13. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    Ok if it needs power to unlock it , use the Com and NO contacts, to feed the lock power.

    see diagram
     
    Last edited: Mar 21, 2014
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