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Mark L

Connecting to the sensors within a security alarm

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Hello,

 

I have a security alarm with wires coming into it from sensors around my house, so rather than duplicate those in z-wave I thought it would be better to try and measure the values of those sensors via a Fibaro module within the alarm.

 

I initially tried the RGBW controller, but this doesn't seem to work as expected, from reading I think because of the pull up resistors within it. 

 

My PIR for example changes from 4.53V to 0V when detecting motion - but if I connect that to IN1 on the module (which due to the pull up resistor, by default shows 10V to ground), then the connection changes from 6.4V to 8.9V - i.e. completely the other way, and therefore does not trigger the alarm (although I can read off the dimmer and see the values change). Is there anything I'm missing to get this working ?

 

If there's no way to use the RGBW controller - I was thinking about the UNIVERSAL BINARY SENSOR. I've used that on another project where there was either an open or closed relay - but I'm not sure how it would work in the above situation ? Plus it only provides 2 channels, compared to the RGBW's 4, but then again I could have 2 of them.

 

Or are there any other better solutions ?

 

Any help greatly appreciated,

 

Regards,

Mark

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Your PIR might indeed have a resistor. It is used by some alarm systems, to detect if someone cuts the wire.

 

This is a related question. Solved by using UBS + find out correct wiring...

 

 

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  • Hi, Thank you for your reply. I've read that article although don't completely understand it. I think on the alarm side, the inputs from the sensors need to be unchanged so the alarm still works. As you say I think the resister is there to detect if someone cuts the wire, and is on all the sensors, so the alarm system is set up for that. I was hoping I could do everything at the alarm side of things.

     

    Given that the PIR input line changes from +4.53V to 0V when motion is detected, is there anyway of telling that without affecting the voltage (which directly plugging into the RGBW input seems to) ?

     

    Could I for example connect the sensor input to both the security alarm and to an IC7400 NOT Gate, and feed the output of the NOT Gate to the RGBW module - so for most of the time, at 4.53V, the NOT gate is at 0, and when motion is detected, it is at the NOT Gates output voltage. As the IC7400 supports 6 inputs - that would cover the 4 inputs that the RGBW module can take, so I'd just need one.

     

    But the question is - will connecting it to the NOT gate affect the sensor input voltage and hence what the alarm sees. 

     

    I'm no expert so I hope the above makes some sort of sense.

     

    Regards,

    Mark

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    Don't worry, your explanation makes sense!

     

    In that other topic, the user was able to move the resistor from the PIR (input of the UBS) to the output of the UBS. From the point of view of the alarm system, nothing changed. You might be able to do that but then I need more details. Schematic of your PIR would be awesome. Photos of the sensor internals might do the trick.

     

    Your buffer idea makes sense but you need to level-translate to about 12V, something a 74 series cannot do ... If you are an electronics DYI person I can assist you. I think you only need one PNP transistor and a resistor! Please let me know if you are interested.


    Because the IN1 resistance is the main cause of your  problem, you can try my high-impedance buffer, but it is overkill for your PIR.

     

    Components can be bought from several sources, like:

     

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  • Thanks - yes I read that other article as well. I actually don't need a range in this circumstance - I just need to detect on or off (in this case 4.53V or 0V), which seems like it should be easier. In fact it just needs to be 2 values different enough that the dimmerSensor will show a different enough value between the two states. If I just need 1 transistor and resistor, that seems like something I could do.

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    15 minutes ago, Mark L said:

    Thanks - yes I read that other article as well. I actually don't need a range in this circumstance - I just need to detect on or off (in this case 4.53V or 0V), which seems like it should be easier. In fact it just needs to be 2 values different enough that the dimmerSensor will show a different enough value between the two states. If I just need 1 transistor and resistor, that seems like something I could do.

     

    Let's go for it... But first, can you please do 4 simple measurements? I'd like to find out if something is really high-impedance... Can you please connect everything as shown, then measure voltage between A and +12V (PIR on and off) and then between A and GND (PIR on and off).

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  • Thanks for your help. There's a bit of a complication in that in the lounge there are 2 PIRs at opposite corners, but only one set of leads into Zone 1. From testing both PIRs need to trigger for Zone 1 to show as an alarm. There seems to be only one set of wires coming into the alarm though (as all the other zones are accounted for), so I'm assuming there must be some connection between the two PIRs.

     

    Re. your diagram, 12V-Gnd is actually 13.87V.

     

    The values when not connected to RGBW IN1 are:

    A-13.87V = -9.33V

    A-Gnd = 4.53V

     

    Due to distance, I can't read the meter and trigger the alarm at the same time (believe me I've tried !). I'll need to wait for my son to get home from school and have him run around. I think though A-Gnd goes to 0.

     

    The front door sensor which I can trigger is similar - when the door is shut:

     

    A-13.87 = -9.33V

    A-Gnd = 4.53V

     

    And when open:

     

    A-13.87 = -13.74V

    A-Gnd = 0V (well 5mV but that's probably my meter)

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  • I can confirm the -13.74 when the PIR is activated between A and 13.87. So I think as the PIR activates a relay to remove the connection, that wire is effectively unconnected to anything.

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    Thanks. I am not 100% this will work, but it won't cost you a lot of money... only some time...

    I think you should be able to measure about 1 V (alarm) and 5 V (no alarm). I hope the transistor reduces current enough to make your alarm happy...

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    Edited by petergebruers

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  • Hi, the components have arrived and I've just tried to replicate your diagram. When there's no alarm, so previously 4.46V at PIR OUT, now I see 12.82V at PIR Out and 13.72V at IN1.

     

    When triggering the alarm, I could see no change at IN1. If I removed PIR out from R1, I see 10.36V at IN1.

     

    Maybe I've got something wrong. On my breadboard, the 2N3906 has the flat edge to the right based on your diagram above. R1 is connected to the middle PIN, and R2 to the bottom pin.

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    You did not do anything wrong, I made an error on the schematic. Pin 2 of the transistor should go to GND, not +12 V. If have corrected the schematic. The resistors limit the current, so that should not have caused any damage (I knew I had to put those resistors in for safety...). BTW some versions of the 2N3906 have different pinout, but let's assume that is not the case.

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  • Hi - I'm kind of glad that's the reason, I spent quite a while trying and failing to understand how the original circuit would work!

     

    I reconnected it as per the adjusted diagram and it now works perfectly thank you:  

     

    IN (ALARM) is at 4.47V normally and ~0.18V when triggered. I did a walk test, and it still triggers the alarm when the PIR triggers, so that's good.

     

    IN1 (FGRGBWM) is at 5.22V normally and ~1V when triggered. Which is plenty to trigger an event in my home automation system (Z-Way/RaspberryPi). In case anyone is interested, the binding for IN1 is:

     

    zway.devices[19].instances[2].commandClasses[38].data.level.bind(function() {

     

    Thanks for your help. I used 0.25W resistors - I haven't calculated the power usage of this arrangement, but I'm assuming it will be low/negligible ?

     

    So now I need to wire 4 of these up for the 4 input signals I want to monitor. x2 for the two alarms in my house. I guess I could use a breadboard as I did for testing, or is there an online PCB constructor you know of maybe? Thanks again.

     

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    20 minutes ago, Mark L said:

    Hi - I'm kind of glad that's the reason, I spent quite a while trying and failing to understand how the original circuit would work!

     

    I am really, really sorry I wasted your time... I thought: "let's make a proper schematic in KiCad instead of a doodle on some paper". And then I introduced an error... Tssss...

     

    23 minutes ago, Mark L said:

    I used 0.25W resistors - I haven't calculated the power usage of this arrangement, but I'm assuming it will be low/negligible ?

     

    Under normal circumstances... Current is about 1 mA through 330 ohm that's less than a milliwatt.

     

    24 minutes ago, Mark L said:

    I guess I could use a breadboard as I did for testing, or is there an online PCB constructor you know of maybe?

     

    Make a PCB is very neat... I wish I had the time and the patience. Because all my projects are single, one-off hobby projects, I do not benefit from the advantages of scale. So I still work on perfboard.

     

    I've heard good things (for beginners) about 

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    I sometimes order from their components store, they're good: 

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    /monthly_2017_11/IMG_20171114_100307.jpg.e38dfee647a7433e19121e9ae61b2788.jpg" alt="IMG_20171114_100307.jpg.e38dfee647a7433e19121e9ae61b2788.jpg" />

     

    I won't win a beauty contest with that, but it works ;-)

     

     

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  • I used a small Elegoo breadboard in the end which proved very convenient - a couple of pictures below.

     

    4 Inputs from the alarm via 4 of the circuits above into the 4 Fibaro Inputs. Works perfectly, my Z-Wave controller can now detect motion in the 3 zones & front door opening, and all still trigger the security alarm.

     

    Many thanks for your help,

    Mark

     

     

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    Hi all, 

     

    I have a similar setup. 

     

    When no motion detected

    A-GND: 0,828V

    A-13,50: - 12,65V

     

    When motion detected:

    A-GND: 1,308V

     

    When connected to Rgbw IN:

    No motion A-GND: 1,229V

    Motion detected A-GND: 1,895V

     

    Would a similar setup work for me as well?

    Regards, 

    Berry

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