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by DaxTrajero
Thu Aug 23, 2018 8:05 pm
Forum: Beginners
Topic: Relay - can it be used in reverse (signal microcontroller) ?
Replies: 3
Views: 237

Relay - can it be used in reverse (signal microcontroller) ?

Newbie alert: Is it possible to use a mechanical relay that, when there's an AC voltage, switches the DC side of the relay? ie. someone turns on a light, and the raspberry pi is signalled

Or is the alternative to use a solid state opto-coupler and resistors?
by DaxTrajero
Fri Aug 10, 2018 9:22 pm
Forum: Beginners
Topic: How to detect an old style wired doorbell only - nothing else
Replies: 20
Views: 979

Re: How to detect an old style wired doorbell only - nothing else

My doorbell uses a Pi. The long leads from the button are connected to the 5v from the pi and a resistor to drive the input of an opto-isolator. One side of the output stage of the opto is connected via a resistor to 3.3V and a GPIO. The other side is connected to ground. When the button is pressed...
by DaxTrajero
Fri Aug 10, 2018 3:45 pm
Forum: Beginners
Topic: How to detect an old style wired doorbell only - nothing else
Replies: 20
Views: 979

Re: How to detect an old style wired doorbell only - nothing else

Thanks for all the info

As a future project, I wonder if its worth removing the chime box altogether...

Wire the doorbell button to the PI

Let the PI talk to something like an ECHO DOT to produce a chime?
by DaxTrajero
Fri Aug 10, 2018 3:33 pm
Forum: Beginners
Topic: How to detect an old style wired doorbell only - nothing else
Replies: 20
Views: 979

Re: How to detect an old style wired doorbell only - nothing else

https://electrical.knoji.com/images/user/danmsnyder/doorbell-transformer-wiring-fbdaee2c.jpg Is the transformer could be ac or dc. Can you check? Basically you can connect and opto-isolator across the bell terminals and connect the output to a gpio. Connect it like a push button. Choose a series re...
by DaxTrajero
Fri Aug 10, 2018 3:31 pm
Forum: Beginners
Topic: How to detect an old style wired doorbell only - nothing else
Replies: 20
Views: 979

Re: How to detect an old style wired doorbell only - nothing else

1. Don't try to put html code in your post. 2. It is unlikely that you can power the RPi from the existing bell transformer for several reasons: a. it may be outputting AC. b. even if outputting DC it is unlikely to be close enough to the 5 volts that a RPi requires. c. bell transformers are usuall...
by DaxTrajero
Fri Aug 10, 2018 2:21 pm
Forum: Beginners
Topic: How to detect an old style wired doorbell only - nothing else
Replies: 20
Views: 979

How to detect an old style wired doorbell only - nothing else

(updated) Hi Everyone Just need a small bit of advice to get going. Not looking to fit any fancy camera/remote doorbell. Simply want to use a PI to detect when the old style wired doorbell button has been pushed. The wired doorbell button is wired to a chime in the hallway. There's two wires leading...

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