Interfacing to alarm system - Raspberry Pi Forums

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hello everyone!

interface our alarm panel pi's gpio.

has dedicated assignable (digicom) outputs appear ideal hooking key events i'm interested in. outputs rated in installation manual 100ma @ 12v.

manual states:
they @ +12v , switch 0v when active. outputs can inverted switch 0v +12v when active. each output source 5ma in +12v condition , sink 100ma in 0v condition.
i've read quite few posts (including one: viewtopic.php?f=37&t=92475) suggest using optocoupler , think understand isolation aspect of (with basic electronics knowledge!), question above information can these outputs directly connected pi's gpio suitable resistor etc. safely or optocoupler still preferable?

main board has fuse auxiliary 12v rated @ 1a. board schematic can found on page 6 of installation manual: http://www.krypto-security.com/installa ... manual.pdf

presumably, if going connect directly panel, take connection auxiliary 0v on main alarm board 1 of pi's common ground gpio pins.

if isolation required project looks interesting: http://www.peterlelie.de/raspi/qdigin/

many in advance help!

thanks.

hello, using optocoupler idea.
possibly work voltage divider ( alarm out -- [9k] ----gpio -- [3k] --gnd ). voltage divider gives 3v when 12 v on input. safety, add schottky diode gpio 3.3v, anode on gpio. diode prevents power pi gpio pin when pi not on power.
of course, gnd between systems needs connected too.

or use 2n2222 transistor, base 10k alarm out, emitter gnd, collector on gpio , enable internal pullup. avoids reverse power gpio.

regards,
gerhard


raspberrypi



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