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Reed switch

Discussion in 'General Electronics Discussion' started by gregrae, Nov 12, 2015.

  1. gregrae

    gregrae

    67
    1
    Jan 12, 2011
    I am going to install magnetic reed switches on all my garage and doors to my house.

    I have a home security system 12v DC .
    The reed switches I require is 21 v DC no .
    The ones I have looked at are 100v . Can I use this voltage reed switch as I cannot find 12Vdc reed switches .
    Can you supply me with Information on this question.
     
  2. duke37

    duke37

    5,213
    718
    Jan 9, 2011
    Perhaps you are getting confused between a reed switch and a reed relay.
    A reed relay has a reed capsule surrounded with a coil to provide a magnetic field. This coil has a specified voltage.
    A reed swich has just the capsule and needs to be placed close to a magnet to activate it. I would think this is what you would have on your doors.
    The capsule will have a maximum voltage and current that it will switch reliably, it seems yours will switch 100V so will handle 12V with ease.
     
    davenn likes this.
  3. gregrae

    gregrae

    67
    1
    Jan 12, 2011
    Thank you for pointing out the switch that I can use.
    The one I am looking at , will this do the job.
    This is the number of the reed switch I am looking at on EBAY.
    I have attached a photo
    361400580783
    Could you advise
     

    Attached Files:

  4. AnalogKid

    AnalogKid

    2,297
    646
    Jun 10, 2015
    That is a standard, simple reed switch and a magnet. For a door or window or whatever, the magnet goes on the moving part and the switch goes on the frame or jamb or whatever the stationary part is.

    The switch doesn't "require" any particular voltage or current. It probably has voltage and current ratings - these are limits not to be exceeded. For example, the switch might be rated at 1 amp. If so, it will work fine with a typical alarm loop current of 10 mA.

    Shop around. The one you show is very expensive.

    ak
     
  5. gregrae

    gregrae

    67
    1
    Jan 12, 2011
    Where can I get better price
    I will be looking for 6 off
    I am upping the security on my house as I have been broken into 2 weeks ago and 5 other times in 15 years.
    I have CCTV SYSTEM 8 off cameras IF
    Alarm system that rings me
    Security screans
    A dog
    Putting reed switches on all doors now.
    If you have any other ideas please tell me. Other than moving .
     
  6. duke37

    duke37

    5,213
    718
    Jan 9, 2011
    You say The reed switches I require is 21 v DC no .

    If the no means normally open, then the reference you give to the reed switch is no good, these are normally closed.

    I would think that normally closed reed switches would be used since if the visitors clipped a wire, the alarm would sound.

    If you only want six, the price is not too unreasonable, they would cost more to fix.
     
  7. AnalogKid

    AnalogKid

    2,297
    646
    Jun 10, 2015
    The switch itself is normally open. It is held closed by the magnet on the door jamb or window frame. The switch opens when the door is opened, the loop opens if a wire is cut, etc. No matter what the cause, open = alarm.

    The next layer of sophistication is to put a resistor across the farthest switch in the loop, and change the loop sense circuit to a window comparator. In this way a shorted loop is another kind of alarm. Useful in industrial situations where someone is trying to defeat the alarm system.

    ak
     
    davenn likes this.
  8. gregrae

    gregrae

    67
    1
    Jan 12, 2011
    I. Do not understand about your loop system .
    Could you give me a digram please.
    Do I use this loop on reed switches.
    The reed switch I have nominated would this be ok to use.
    As I have 3 roller doors and 2 swinging doors.
    Thank you all
     
  9. AnalogKid

    AnalogKid

    2,297
    646
    Jun 10, 2015
    In a security system for a home, usually groups of doors or windows are combined. For example, all of the windows on the 2nd floor are connected together in a series string of switches. As long as all of the windows are closed, the loop is closed. If any window opens, the loop opens and triggers an alarm. In this way you can protect multiple windows with only one input to the alarm controller. The tradeoff is that when there is an alarm, there is no way for the alarm controller to determine which window is open, only that it is somewhere on the 2nd floor.

    ak
     
    davenn likes this.
  10. davenn

    davenn Moderator

    13,264
    1,749
    Sep 5, 2009
    which is why zoned alarm systems are used ... so that alarmed areas can be narrowed down easier :)
     
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