ARMAC has come about through a process of innovation. Inevitably this has meant that its initial design has been challenged and changed, in fact evolved, through a series of development stages.
Because of this process, the system has become more sophisticated to deal with both encountered challenges (such as voltage spikes when the pump is cranked) and further stages of protection (for example giving the system autonomous capabilities if manual control is impossible due to breakdown of communication with the external world). Design improvements have led to much more efficient, robust, and in some cases considerably simplified design.
One example is the evolution of the arrangement of communication between electronic modules. Originally command of the system was to be applied from a module in the house, connected to the internet on the one side, and via relays in the pump shed to the sensors and valves of the sprinkler system. This required a 13 core cable to be laid between the house and the pump shed and two micro computers (Arduinos) in the house to operate relays and analyse sensors inputs over the 10 meter 13 core cable. In the end however, this proved insufficiently robust.
In the current arrangement the house electronics simply sends commands and receives information from the modules in the pump shed. The pump shed modules deal with operating the valves, receiving and analysing sensor data, and also making all pre-programmed decisions based on this data, and then directly commanding the relays. This information transfer requires only two (“A and B”) wires, operating a little like a telephone with RS485 transceivers at each end. This communication system is much more robust and also flexible, since capability is not limited by the number of available wires. In the shed one microcomputer analyses sensor data, whilst the other makes the autonomous decisions when required, and commands the relays. This also allowed major simplification of one of the microcomputer programs, dropping it from around 3,500 lines of code to 1,300 lines.
These notes describe the system in its current development stage. However, where appropriate some note is made of earlier considerations and decisions how those have now been modified.