Arduino + Drycontact alarm system

Hi, I want to integrate my home alarm system with arduino. I don't have the installer manual of the unit Tecnoalarm TP5, and the manufacturer is telling me that they only give information to certified installers :( But they say that the central have several Dry Contacts that give information if the alarm is triggered or not.. I'm not so sure what dry contact means, but for those of you who knows ....

how do i connect this dry contact to arduino and check if is on or off ?

thanks & Regards.

That means it's turning on a relay. The relay might be dealing with 120 volts, so you would want to test the connections with a multimeter to figure it out. Is there an LED that comes on when the alarm is triggered? If so, you could directly connect the arduino to the LED, or any other low-voltage part.

And if it trigger a relay, for what i read the dry contact has no power flowing.. where do i connect the relay on arduino ? how to check if relay is on or off ?

You would want to use a multimeter first. If you were to connect 120 volts to your arduino it would catch on fire. You should use the multimeter to examine different connections with the alarm off, then compare it to when the alarm is on. If you see a connection somewhere with 5 volts or less you could connect the arduino to that. If you can look on the back of the relay you should see some soldered areas, use your multimeter to test those.

if the contact/relay has no current.. you only open and close ? how can i check this ? Check the voltage between any connections you have access to.

eheheh nice link about multimeter... in the multimeter you have an dial that beeps when both + and - touch ... Continuity Test ... how can you do this with arduino pins ?


Hi, ok i founded i have an contact that in nomal status give 13v and when the alarm fires it goes to zero....

so i may do a voltage divider and if zero volts, alarm triger ? or i may use that 13v to give a relay change status from open to close

and use 2 pins of arduino connected to relay, one in read other in write so when relay closes i can see that the other pin is high ..

Does this make sense, or better ideas ?