I am wanting to integrate my tecom challenger alarm with my PC and am after an I/O board. So far, it looks like the Arduino Mega might do the job.
The tecom challenger alarm has inputs and outputs. The inputs require a dry contact and simply read resistance (open/closed). The outputs will use a relay that takes 5V and can output any voltage. However, i do not want to output a voltage i want to simply use a dry contact as well.
Therefore, i would like to know whether the Mega board outputs a voltage over the digital/analogue outputs, and whether it requires a voltage through the digital/analogue inputs. Or will a dry contact work.
To go from an Arduino output into the alarm input, you could use small, sensitive relays that could be driven directly from an Arduino digital output pin.
I assume from this comment that the digital pins output a very small voltage? Do you know how much?
Be sure to turn on the pull-up on the input pin(s) so that you can detect between the alarm closed and open.
Are you referring to the analogue pins?
Do the analogue input pins simply require a dry contact? As mentioned in my first post, my alarm will output 5V (or 12V) to a relay card that will open/close a dry contact to the Arduino. Therefore i want the inputs (both analogue and digital) on the Arduino to register a dry contact.
Do the analogue input pins simply require a dry contact? As mentioned in my first post, my alarm will output 5V (or 12V) to a relay card that will open/close a dry contact to the Arduino. Therefore i want the inputs (both analogue and digital) on the Arduino to register a dry contact.
All Arduino I/O pins usually require a source voltage to sense. Your application would normally utilize digital pins rather then analog pins, however the analog pins can be programmed to be digital input pins, but that's another story.
Anyway to be able to detect 'dry contact' inputs to a digital input pin requires a 'sense voltage' on the Arduino side. This can be either done with a external pull-up or pull-down resistor connected to +5vdc or ground respectively. However even simpler if you enable the digital input pins internal programmable pull-up then you need no external resistor.
One side of the alarm contacts will wire to the digital input pin and the other contact wire to Arduino ground. When the contacts close the digital input pin will read as a LOW, and HIGH when the contacts are open.
however the analog pins can be programmed to be digital input pins
So they can essentially be used as digital pins and function in exactly the same way?
One side of the alarm contacts will wire to the digital input pin and the other contact wire to Arduino ground. When the contacts close the digital input pin will read as a LOW, and HIGH when the contacts are open.
This is essentially what i am after. The alarm will either open/close the circuit and i can see through my PC whether it is open or closed.
My only problem now is outputting to the alarm. The alarms inputs reads resistance to see whether it is open/closed. For example, a PIR or reed switch simply opens/closes a circuit and in series with a resistor allows the alarm to read an input. I'm thinking a relay may be required (as mentioned in the second post). What do people think?
So they can essentially be used as digital pins and function in exactly the same way?
Yes, however a Mega has so many pure digital I/O pins, why would you have to utilize a analog input as a digital pin?
My only problem now is outputting to the alarm. The alarms inputs reads resistance to see whether it is open/closed. For example, a PIR or reed switch simply opens/closes a circuit and in series with a resistor allows the alarm to read an input. I'm thinking a relay may be required (as mentioned in the second post). What do people think?
A low coil current +5vdc reed relay would be the simplest method:
That one only requires 10ma of coil drive current, so a Arduino digital output pin and drive the coil directly. One should still wire a reverse connected diode across the relay coil terminals for spike suppression. The contacts of the relay would then wire to your alarm input.