Alarm State Machine / Group Zones Example

Just to update of gateway configuration page,  I've created a state machine diagram showing arm/disarm cycle.Also here is an example of my own groups (Garage, House) and zones (PIR, reed) setting for ground floor. You can see here how authentication unit is attached to particular zone. Only these zone is then set up with authentication delay. That is, when someone trips these zones there is time allowed for the person to authenticate. All other zones in house group trigger the alarm state immediately. You can read more about it in zone's setting.

 

Remote zones

Recently I have started to play with feature that was on my list for long time. That is remote zone. To introduce it a little, on beginning I had in mind 2 general types of zones. Local zones are directly connected to gateway hardware. These can be build in 8 analog plus 4 digital zones, or zones connected by I2C expansion connector. Then remote zones connected either by RS485(wire) or wireless zones. Connection type does not matter to gateway, but such zones can be divided to two groups by reporting state. One group would report fully its state, that is it will report every change of state out of OK, PIR or Tamper. The other, battery powered remote zones, will only report alarm states such as PIR or Tamper. Gateway will then automatically change the zone state to OK if there is no event received for 2 seconds.

Remote zones brings new possibilities, you can build yourself a wireless PIR and add it to your gateway. Or you can build remote expander, either wired or wireless that will extend you zone count. Imagine you have barn near by, and you have only 4 wires connected to barn, that is only enough wires for authentication node. Now you decide you need two analog plus one digital zones there. Simply enough you connect such zones, with some little protection circuity, directly to authentication node. Add code to authentication node to include zone registration plus zone state handling, and you have 3 new zones connected.

I have here on my desk for test a battery powered remote zone, as shown on
picture. It is running for some days, and seems to do its job properly. I use Chinese all-in-one PIR sensor AS312 attached to PIR shell by hot glue. For this purpose I have modified standard battery node code and added zone state handling, based on interrupt signal coming form PIR sensor. The node does also temperature and humidity monitoring out of external SHT11. Battery life seems to be reasonable, with some modification it could last few months with 700mAh Li-Po. This is tempting, it would be nice to create rechargeable wireless PIR sensor that could be placed into standard commercial PIR shell :). I will publish the code to GitHub as example code.

Registering is same as for sensors. As soon as the node is powered up it will send registration packet and gateway will add a zone in zone tab. Then you can set attributes as for any other zone. Zone setting are sent back to nodes as master copy, and on next power cycle the zone is registered with newly stored  attributes. There are enforced rules for remote zones during registration, such as analog digital flag on bit 15 and it is based on registration  type ('A' or 'D'). Or remote zone flag on bit 12 is set On, and present bit flag on bit 14 is set On. Zone number cannot override any local zone, that is it cannot be lower then 13, or cannot override existing I2C zone. Zone last OK and PIR timestamps are set to registration time. Sleeping battery powered remote zones share the same message queue as sensors, that is gateway keeps registration packet for at least one hour to not loose such packets during node sleep.

Web interface - zones

Zones  are the basic monitoring elements. Currently the only zones present are the ones that are hardwired on the main board. There are physically present 7 analog zones and 4 digital ones. As you can see on the picture there is table that represents the overview of all the zones and their statuses.

The future is open for at least three possibilities that I have prepared already. One is to use shield that communicate over TWI interface. This can be either analog multi channel ADC for analog inputs or TWI port expander for digital inputs. Other would be remote zones tied to remote boards. These board are equipped with extension header to easily break out the SPI, TWI, analog or digital pins. This would also simplify wiring of the distant zones. For now I'm planning to make the second option available. Third would be radio controlled zone, or radio controlled remote board.

But current stage is just the hardwired zones. And the configuration in web interface is as follows. There is zone number witch represent the port on the board and also type of zone. Then there is a zone name which a user can modify and can span over 15 characters. This name is than used when sending SMS messages or is used when reading log over web interface to better represent it then just the zone number. Next is the switch that is turning the zone "On" or "Off" and it does exactly this.

Auto arm is telling the system to set the zone to arm status when there is no movement in the zone for specified amount of time. I will use this for garage that is attached next to our house. Next switch is open alarm, that does the opposite. It monitors the zone and when it is open for longer then specified time, it issues a message in log and sends out a SMS. It is intended more for digital zones, such as door switch, and allows the system to let you know that you forgot to close them. Again a garage door is a good example, if you forget to close it and you are already in house, system will notify you.

Authentication delay switch is telling the system, how long it should wait for the authentication if the zone is tripped. This let you easily adjust the timing mechanism of alarm. For example if some one triggers the zone in you front door, you can set the authentication time high. Because you can assume that it is normal pathway. On the other hand if someone trips the zone in your bedroom that has only window, you can set the authentication time to zero. Because you would normally not enter your house through bedroom window(too much beer probably, when yours wife is in her sister). The switch multiply the time set in authentication delay parameter present in global setting.

The last option for a group is to select its superior group. This option telling the system what zones are treated as one area. And when one zone is armed it arms all zones in group.