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Wireless Alarm system

Discussion in 'General Electronics Discussion' started by VincentM, Nov 20, 2015.

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  1. VincentM

    VincentM

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    Nov 20, 2015
    Hi all,

    I wonder if someone could help me.

    I am building an alarm system for my yard - It will consist of 4 x outdoor PIR's (which I already have) - These have normally closed and normally open points. If any PIR has to trigger I want to transmit a signal to the alarm circuit which is located in the house - This needs to be done via wireless (ie. wireless transmitter and receiver)

    My question is, are there any suitable transmitters/receivers that I can purchase (models/types)

    Thanks
     
  2. Martaine2005

    Martaine2005

    2,710
    730
    May 12, 2015
    Hi Vincent,
    What alarm circuit do you have?
    What frequency are you permitted to use in your country?
    What distance?
    There are so many transmitters and receivers on Ebay to choose from..

    Martin
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    10,023
    2,136
    Nov 17, 2011
    Lots.

    Cheap and inexpensive: use a wireless dorrbell, connect the relay contacts instead of the pushbutton. This solution is not very secure. Anybody with a suitable transmiter can either set off an alarm or jam the receiver so it cannot detect the true alarm signal.

    From there on you can buy ever more sophisticated wireless transceivers using Zigbee, WIFI, Bluetooth or whatever. You can incorporate a higher level of security at the cost of more expensive wireless modules and some effort on the receiving end to decode the wireless messages and act accordingly (using e.g. an arduino, a Raspberry Pi etc.)

    Possibly for your application the simple wireless doorbell wil be sufficient - just a guess.
     
  4. Martaine2005

    Martaine2005

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    May 12, 2015
    Haha, we have to stop minute meeting Harold!

    Martin
     
  5. VincentM

    VincentM

    6
    0
    Nov 20, 2015
    Hi Martin,

    Thanks for your reply.

    433Mhz is permitted in SA.
    A max of 20 meters

    I need guidance on choosing the correct transmitters and receivers (I am trying not to use Arduino or likewise)

    Thanks
     
  6. VincentM

    VincentM

    6
    0
    Nov 20, 2015
    Hi,

    Just had a look at that on Ebay now. There are 3 connections on the board - VCC, GND and Data. What type of signal is it expecting on the data pin?

    (Please pardon my ignorance):)

    How would I be able to trigger this in an alarm condition
     
  7. Martaine2005

    Martaine2005

    2,710
    730
    May 12, 2015
    Hi,
    I would imagine it's the trigger.
    It can also be used as a remote switch too.
    Search for 433mhz transmitter modules and you'll see hundreds. Have a read.

    Martin
     
  8. VincentM

    VincentM

    6
    0
    Nov 20, 2015
    Hi,

    could this trigger perhaps be just a negative or a positive pulse supplied when the PIR sensor is triggered?:)
     
  9. Martaine2005

    Martaine2005

    2,710
    730
    May 12, 2015
    That appears to be all.
    A high or low from a microcontroller to use as a switch.
    I am not sure if it's needed.
    Possibly just live trigger from your pir.
    Did you search and have a read?
    I can't find the time to read and relay what I've read at the moment.

    Martin
     
  10. VincentM

    VincentM

    6
    0
    Nov 20, 2015
    I have been reading and it seems like the data pin needs an input signal from some electronic device eg: MCU or arduino.

    So I guess this is not really what I am looking for
     
  11. Harald Kapp

    Harald Kapp Moderator Moderator

    10,023
    2,136
    Nov 17, 2011
    Go ahead...
     
  12. Harald Kapp

    Harald Kapp Moderator Moderator

    10,023
    2,136
    Nov 17, 2011
    It is not important where the signal on DATA comes from as long as it is within the voltage limits of the DATA input.
    You can connect the DATA input to Vcc of the transmitter via the normally open contact of the pir's relay to generate a logic high level when the relay is activated.
    Connect DATA to ground (0V) via a pull down resistor to ensure logic low level with the relay being inactive.
     
    Martaine2005 likes this.
  13. VincentM

    VincentM

    6
    0
    Nov 20, 2015
    Wow... Thanks.

    If that is the case then this is exactly what I am looking for.:D
     
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