I have a GSM RTU unit which sends out SMS alarm if it receives a trigger voltage.
The manual says that it accepts dry contact.
The RTU unit has digital input port (DI0) and Ground (GND) which if shot will send out SMS alarm.
I was informed that the DI0 expect 5V digital input for triggering the SMS alarm.
I’ve set up an arduino UNO and a NPN transistor to act as switch.
I’ve got the "RTU DI0 and GND" working, sending out alarm as intended if the DI0 and GND is shot.
I’ve also got the "UNO + NPN circuit" working, a LED between emitter and collector lit current flow to base.
Now i'm stuck at where should the DIO and GND of the RTU be wired to in the “UNO + NPN circuit”.
I’ve attached a scenario diagram.
I’m a newbie. Forgive me if the question is too basic.
Appreciate any advice.
I don't think that part will do much after you shoot at it's pins.
Usually you'd have to connect that DIO pin to one of the Arduino's outputs, and connect grounds. Your unspecified part may be different, and it may expect a 3.3V signal rather than a 5V signal. In neither case I see why you'd use a transistor in that connection.
Thank you wvnarie. Sorry, i should have mentioned in my earlier posting that I will later connect the analog input of my UNO to a current sensor, hence the use of the NPN as a switch to automatically send trigger pulse to the DI0 of the RTU. The RTU does not has an analog input and that was the only reason i had to use Arduino.
You're now making even less sense. Largely because I'm quite sure you're leaving out about 80% of the information you have about the project. Possibly more than that.
