Hi - I'm very new to electronics - I'm a software person - so that part is not so scary to me - but I love the idea of embedded systems - I have been studying the electronics side - but there's a lot to learn - Anyway -
I have a Netduino Plus 2 - and I have a driveway alarm (Dakota Alert Receiver) WR-3000. The Dakota alert has a Relay for 4 ports - each relay having an NC,NO, and COM wire connection.
The ports on my receiver have a Driveway sensor on one - and a motion detector on another - so I have two IO's that I want to monitor. The driveway alarm fires when a car is about 600 ft away - and the motion detector fires when a car or a deer is about 80 ft away. Which is great - but I don't really care about the motion unless the driveway alarm fires first... so I need some logic in there somehow. Right now - both alarms go off all of the time for every event - which is not real practical.
The Relay specs are 24VDC 3a (which I don't really understand because the receiver is powered by a 12VDC power supply)
I want to set an interrupt on each relay when it goes hot - and trigger an event. So - unlike everything I've found online in dealing with relays - mine happens to be an INPUT.
I've calculated the Voltage Divider - that a 4.2k ohm and 1k ohm resistors will drop the 24VDC down to 4.21 - is that ok?
But my big question is - how do I wire up to the Netduino? If I use a Voltage Divider circuit - I can bring the voltage down to between 3.3 and 5 v - but .... do I just connect the NO wire (after the 4.2k ohm resistor) to a GPIO port? But where do I complete that circuit (after the 1k ohm resistor) on the Netduino? And do I need to wire up the COM on the relay to somewhere on the Netduino? And since - I have two of these - can I combine the COM into one hookup on the Netduino?
Thanks much for any input.