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Very simple relay wiring question

Discussion in 'General Electronics Discussion' started by HiFiGator, Apr 5, 2012.

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  1. HiFiGator

    HiFiGator

    3
    0
    Apr 5, 2012
    I have a decent understanding of electronics, but having been in sales rather than installation, the nuts and bolts of wiring are certainly not my strength. Anyhow, what I want to do is very simple and I'm almost postive that I should be able to do it. In any case, we lost a number of electronics from a lightning strike a couple of weeks back. From simple deductive reasoning, I think the surge came in through phone lines. It took out the modem, our phone system, my ipod cable (but not the ipod itself) and a control panel in one of our alarm systems, among other things. The Ipod was plugged into the same wall socket as the phone system control box and of course, everything else was connected via phone cables from there. In any case, whether that was the path, really doesn't matter. I have pieced the alarm back together, but it is cumbersome at the least. The short question is that I have a couple of "zone expander" boxes and they still work perfectly, but they are designed to connect into a main alarm control board. Not only do they no longer make the model we had, they are also rather expensive and since we pieced our system together, we were really never using much of the main brain anyhow. The expander boxes monitor their zones independently. They provide automatic bypass should a zone continue to alert, and they also provide memory to let us know what zone(s) was/were triggered. Incidentally, this is a 12V system which is powered with deepcycle batteries that are charged with a maintenance free, completely automatic charge system. Again, we have 48 hours of backup, should power fail completely. In any case, here is the simple wiring question:

    What I need is to wire up a relay to each of the expander boxes so that they will trigger a 12V signal -- not that it matters, but I could use a positive or a triggered ground -- when they receive either an open or closed circuit from the expander box. I know I should be able to do this, but keep spinning my wheels.

    If possible, I want to use the 5-pin Bosch relays. Not only do I have them already, as well as pre-wired sockets for them, but they have proven to be very reliable,

    The pins are labeled 30, 85, 86, 87 and 87a.

    Again, I have access to 12V right there, and everything operates on DC 12V. The trigger out of the expander boxes can be either a common and closed circuit or a common and an open circuit. I should be able to do what I'm trying to do. The bottom line is that some configuration of the 5 pin relay should work as I need, and that is to throw 12V signal when receiving either an open or closed circuit signal.

    Sorry about the lengthy post, but I just wanted to give you the insight, in case it matters. Thanks!


    5 Pins from Bosch relay:

    30 -- ???
    85 -- ???
    86 -- ???
    87 -- ???
    87a -- ???

    Thanks again!
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    10,609
    2,370
    Nov 17, 2011
    Look here: http://www.ripper1.com/tech/wiring.php
    There you will find some information on wiring especially with respect to Bosch relays.

    About 1/3 down the page there is a wiring diagram for the Bosch relay. Note the diode which is not part of the relay but must be provided (freewheeeling diode) by you to protect the controlling equipment from overvoltage when the relay is turned of. It doesn't matter how you connect the diode to the relay. However, when connecting the diode/relay combination to your controller, make sure that the cathode of the diode (that's where the dash is in the symbol - the real diode has a ring here) is connected to PLUS of the controller (that is, the diode will not be conducting when the relay is operated, only when it is turned of - the reverse voltage is induced by the relay coil at that moment).
    So if you apply 12 V between pins 85 and 86 the relay will trigger.



    I hope that helps

    Harald
     
  3. GreenGiant

    GreenGiant

    842
    6
    Feb 9, 2012
    [​IMG]

    I think that should answer your question.

    but to clarify further:

    30: common input (ground or +12 volts)
    85: coil positive or ground (opposite of 86)
    86: coil ground or positive (opposite of 85)
    87: NO contact
    87a: NC contact
     
  4. HiFiGator

    HiFiGator

    3
    0
    Apr 5, 2012
    Thanks for the prompt response, but something has to be missing there, but it's probably because I didn't explain the issue accurately enough. the "trigger" from the expander box is an ultra-low (few millivolts) signal -- not enough to do much of anything by itself, but it will trigger circuits in alarm control panels. Also, there HAS to be a thrown signal lead as well, that will only go hot when the alarm is triggered by the open/closed circuit feed. So there has to be a minimum of four lead connected, unless I'm missing something. There has to be a constant power and constant ground and then there has to be a trigger in from the expander box, and then there has to be the thrown signal from the relay that goes hot after the relay gets triggered from the open/closed circuit.

    The "common" lead could easily be connected to the same pin as the constant ground from the power supply, but there still have to be 3 other leads -- constant 12V, low voltage open/closed cirtcuit trigger, and the thrown signal from the relay. Correct?

    Thanks again for the help.
     
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    10,609
    2,370
    Nov 17, 2011
  6. HiFiGator

    HiFiGator

    3
    0
    Apr 5, 2012
    Harald Kapp wrote:

    Look here: http://www.ripper1.com/tech/wiring.php
    There you will find some information on wiring especially with respect to Bosch relays.

    About 1/3 down the page there is a wiring diagram for the Bosch relay. Note the diode which is not part of the relay but must be provided (freewheeeling diode) by you to protect the controlling equipment from overvoltage when the relay is turned of. It doesn't matter how you connect the diode to the relay. However, when connecting the diode/relay combination to your controller, make sure that the cathode of the diode (that's where the dash is in the symbol - the real diode has a ring here) is connected to PLUS of the controller (that is, the diode will not be conducting when the relay is operated, only when it is turned of - the reverse voltage is induced by the relay coil at that moment).
    So if you apply 12 V between pins 85 and 86 the relay will trigger.



    I hope that helps

    Harald



    Thanks a lot! That was exactly the kind of link that I've been looking for. Now I'm going to give it a shot! (Figuratively, of course.) In fact the running joke here for the past couple of weeks has been that "since the alarm wouldn't 'arm' then I had to" -- meaning that since I had to stay at the store overnight, then I had to arm. I had my .38 special, 9mm and 12 guage all locked and loaded ... but dammit, no one tried to break in!

    Thanks again for any advice.
    Incidentally, I'm not 100% confident that this will work. In fact I could have sworn that I tried that particular wiring, but I've gotten so friggin' confused messing with this stuff for the better part of two weeks, that I don't know which way is up. Time to try it. (fingers crossed) ...
     
  7. Harald Kapp

    Harald Kapp Moderator Moderator

    10,609
    2,370
    Nov 17, 2011
    Good luck

    Harald
     
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