D8x alarm system and outputs

Hello

I have been reading the manual for the D8x alarm system. I am trying to arm/disarm the system with a dry contact then output the status of this arm/disarm to an electronic device I have which will communicate this via MQTT (I am using a Shelly 1 device to perform this function). I have attached my schematic for your reference.

Two questions I have:

1. When shorting Z8/COM (dedicated key switch input), are these terminals internally current limited? The manual states to wire these with a resistor in parallel, which is not going to current limit when the pins are shorted. Can the pins remain shorted (i.e. latched)?

2. The manual states that AUX1 is an open collector output. Does this mean that when AUX1 is initiated, it will conduct to ground? So in other words, assume the SW terminal has 12V DC on it from the Shelly, current will begin to flow through AUX1 to ground once the output initiates?

Thanks

 

Yes, inputs can be shorted permanantly to ground. The resistor is an end-of-line termination (it should be at the switch end) and detects if someone cuts the wire. You will need to set zone 8 to an arm/disarm change over switch.

From the limited documentation it appears that the SW input is biased at 1/2 the supply voltage and can be pulled either high or low to trigger the input, so connecting it directly to the aux 1 input should work as required. However I would be dubious about connecting any non isolated external device directly to the alarm panel ( the zone is fine because the shelly has an isolated relay output). I would get the relay output expander module and use the relay contacts to trigger the sw input. You could of course just buy a small reed relay and hook it up yourself (with a protection diode).

 

Thanks for the reply. I've revised the schematic to include an isolating relay.. does this look okay?

Actually that might not work, not sure if the Shelly 1 can drive the coil.... Maybe I'll use an opto coupler

 

The relay is back to front.

The relay coil goes from the +12V to the Aux1 output (the output is energising the coil). You don't need the resistor in series with the coil. Make sure the relay is 12VDC. The diode cathode (bar) goes to the +12V side of the coil

The relay contacts connect to the SW input and 0V.

 

Thanks for that - I will try a reed relay

 

You can get boards like this that make installation easy:

https://www.altronics.com.au/p/s4442-12v-single-dpdt-relay-board/

 

Thanks for the info, just wired it up and it works very well!