Case Study: Control Circuit for Domestic Sprinkler Device: Plumis (Automist)

Case Study: Sprinkler (fire prevention without damage)

Water damage from sprinklers is often as severe as fire damage, but the Automist sold by Plumis provides for a fine water mist that both controls and extinguishes fire whilst minimising water damage. The system works for a domestic water supply via, for example, the kitchen sink. Please follow this link for articles from Plumis: Automist Demonstration Articles.

The EM developed the first successful prototypes for this product. 

The Plumis Automist System Development

Challenge: the project for Plumis (Automist) required:

  • AC motor control via PID control loop
  • Solid state component motor control
  • Embedded electronics
  • A complex state diagram to control a system with many modes of operation, all implemented via embedded firmware.

 All this was achieved in a short time frame. 

Method: this product required:

  • Meticulous development of state diagram to define modes of operation and events that needed to cause state (mode) change, i.e., an algorithm. This element was safety connected for obvious reasons.
  • Design and development of electronics that implemented embedded realisation of the algorithm and controlled an AC pump via a control system.
  • Extensive testing of the above.  

Results: All the challenges were met. The resulting prototypes were tested for numerous operations, proving the system. 

Skills: The main skills employed by the Electronics Machine in the Automist design were:

  • Miniaturisation of PCB and PCBA electronics to allow installation in the very limited space available.
  • Optimisation of a heatsink to allow sufficient dissipation of heat yet the minimum possible size to fit into the space available.
  • There was the potential for electric motor transients to cause noise inducing transient noise – EMC issues. The design was optimised and EMC issues avoided.

Journey: Innovative products and designs start in all sorts of different places, but university spin-offs are a common and good one. From the numerous successful products the EM has seen evolve, the single most important starting point is a professional team. The very nature of universities fits hand in glove with this.

Plumis was a London university spin off and showed all the promise at the beginning that it eventually delivered through its company and the Automist product. It is essential that a team with technical credibility, financial backing, and industrial experience is formed as soon as is possible. Plumis did that and benefited accordingly.

Fast iterating prototypes led to a specification satisfying design. A thorough success.

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