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So here's the situation, goons. My grandmother lives in a super, super rural area. But with the natural expansion of the human race, it's slowly becoming more suburban. This means going from a handful of neighbors to a new housing complex behind her; she used to know everyone around her but now the nearby population is set to quadruple and she's nervous about this and wants a bit of extra security. She's allergic to dogs, but wants a 'barking dog' alarm for when people ring the doorbell (It's what she requested, specifically, so I'm going with it). I've found roughly a bazillion motion-detection dog bark alarms, but not a single doorbell-triggered one. So I figured I would just make one. It's been a learning experience but it seems fairly straightforward for the most part. I've got a little recording device (Just a circuitboard with a play button, record button, batteries, and a tiny speaker) that I soldered the speaker contacts to a 3.5mm jack. I plugged the jack into a 2.4ghz wireless transmitter that goes to a stereo system to play the sound back. I recorded the sound from a phone (youtube video) and it plays perfectly when I press the playback button on the recording device. The dog barks, it sounds great, the wireless is fine, etc. The problem is with the doorbell to recorder contact. The contact for the recording device is just a dry contact. My multimeter didn't pick up any voltage going across it. Bridging the contact in any way at all (By finger, tweezers, etc) triggers the recording playback. But Doorbells normally have voltage on the button, typically between 10v and 20v. And I know first-hand that inputting voltage on a normally dry contact can cause issues. I'm HOPING the doorbell might have a relay output or something, but I doubt that very much. My question is, how would I go about taking a wet 12v contact (doorbell) and converting it to a dry contact to avoid issues with the recorder circuitboard? khy fucked around with this message at 02:23 on Jan 20, 2020 |
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Jan 20, 2020 02:19
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automotive makes 12v relays for cars that should fit your application. your local auto parts store should have something. ps "wet" in contact terms usually means you're using mercury or other liquid wetted contacts for debounce purposes. not really what you are looking for here. "dry contacts" means literally that. they are dry metal bits that get crammed together to complete an electrical circuit.
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Jan 20, 2020 02:49
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MRC48B posted:automotive makes 12v relays for cars that should fit your application. your local auto parts store should have something. My bad. For my work I spend a fair amount of time working with low voltage security systems/camera systems/door systems. I frequently work with HID Edge Evo EH400-K devices which use jumpers to change between 12V Wet (IE : Power supplied by the controller) and 12V Dry (Externally powered) door strikes/locks. The 12V Wet is for the doors that use strikes, since the strike uses a solenoid that allows the latch to swing free when energized, while the dry is used for our Maglocks which are always energized EXCEPT when triggered. So I'm used to speaking of 'Wet' relays as those that have power crossing over them and Dry as being simple contact relays without supplying voltage. I guess the parlance varies from industry to industry, I just assumed it was always like that when referring to triggered relays. That said! I'm looking at some wiring diagrams right now and I THINK I understand how it works, so I'll pick one up tomorrow and give it a try! Thanks for the advice!
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Jan 20, 2020 03:03
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