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Tried using a relay module to tie in an old POTS line alarm panel...
Hooked up a 12V relay to a DSC 1864 in a house off Route 9 last week, but the thing kept chattering every time the AC kicked on. Turns out I forgot to put a flyback diode across the coil, which is basic stuff I know. What do you guys use for isolating old phone line triggers without issues?
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bennett.mason25d ago
Wait, you mean people actually skip the flyback diode and wonder why their relays sound like a dying cricket? (I definitely learned that one the hard way too, don't worry.) For POTS line isolation, I've had good luck with those little optocoupler boards, the 4N35 or PC817 types, just slap one between the alarm panel and the phone line and call it a day. They're dirt cheap and won't chatter even if you plug a blender into the same circuit as your alarm. Plus, you don't have to worry about back-EMF frying your reed switch or whatever else you've got hanging off the phone line. Just make sure you read the datasheet for the current limiting resistor, or you'll smell the magic smoke like I did once.
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gavin69225d ago
Yeah @bennett.mason I learned that smoke trick the expensive way too, guess that's what I get for skimming datasheets.
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