Troubleshooting DSC Alarm Panel Interface

[gyorgy]

Hi! Can you please help me troubleshoot my Arduino Uno circuit? It interfaces with my alarm system and sends via WiFi the alarm messages to an MQTT broker. I use the relay to detect when the alarm fires by detecting the signal the alarm panel sends to the siren. The alarm has 12v logic so I use 10kohms voltage dividers to drop the voltage going to digital inputs 2 and 4. Everything worked fine for a few days but then the Arduino got fried. I haven't been able to pinpoint the problem.

Any help would be greatly appreciated. Thanks

[TomGeorge]

Hi,
How have you got the siren relay wired?

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
(Not a fritzy diagram)

Thanks.. Tom..

[gyorgy]

TomGeorge, here you go.

[outsider]

If voltage on DATA is 12V, voltage on pin 4 is 6V, too much, 5.5V MAX, make R2 & R4 6.8K.

[TomGeorge]

Hi,
OP's circuit.


If you want to use that relay sensing the siren, then I suggest my modification, this will completely isolate the BELL from the UNO, 10K might work,if not try 4k7 , or 1k.
Modified Circuit.


As outsider has said, you need to recalculate your potential divider to get 12V to 5V.

Tom....

[gyorgy]

Tom, Outsider, thank you for your help.

Gyorgy

[hpapagaj]

Hi György,

I want to connect to my DSC from my Arduino. What do you think, can I connect right before the Keypad? It is easily accessible to me, the main alarm not.

My other question: DSC doesn't complain about the Arduino? I read somewhere that keypads are programmed to the alarm, if you remove or add one then you must pair it with master code.