The brief here was for a range of sensors for water management in washrooms, including zone controls and individual controls for taps, showers, urinal and WC flushes.

The sensors are conventional passive and reflective designs, however the challenge was in keeping to robust and well-proven design techniques whilst achieving the performance and rich feature set required by the client. We find these challenges great for innovation.

Aspects of the design that make these products stand out from the crowd include:-

  • rich functionality such as dual flush, flush arrest, hygiene flush, syphon trap refill, cleaning lockouts, hand or body sensing, etc.

  • a bespoke 2-wire free-topology power&data bus, providing a network connection to each sensor without any additional wiring.

  • highly configurable, either manually, by infra-red remote control, or over the network.

  • highly flexible, allowing their use in unusual and demanding applications.

  • node interaction, e.g. multi-sensor zone control, and synchronised hygiene flushes.

  • optional BMS and internet connectivity for remote monitoring, control, and alarms.

  • reduced cleaning and maintenance costs, because remote monitoring allows site visits as required, rather than to a regular schedule.



As you can see, the PCB designs are necessarily compact, yet include an ATMega8 processor, power management, a robust solenoid driver, and a network interface. The key here was achieving high component and tracking density, yet ensuring ease of manufacture to keep costs low and reliability high.

The sensors are extremely robust, as they are installed in harsh environments by some pretty unskilled plumbers. They are very easy and intuitive to use, will withstand all kinds of incorrect connection and operation, and have excellent noise immunity (EMC).

They are selling in the tens of thousands, yet we are seeing very few problems and a negligible failure rate – exactly as it should be!

Ben Mack, January 2013