Introduction:
This ventilator as used in horticulture did require an upgrade as the original design did not change much in the last 15 years. Now that much more power full microcontrollers are available the control algorithm can be improved to achieve a better stability in glass houses ventilation compensating for changes in mains supply voltage. This redesign also gave the opportunity to increase the reliability of the controller by choosing other components including a remote control through USB, Bluetooth or WiFi. The default control input is a 10 .. 200 Hz TTL signal provided by a climate computer.

A number of very specific design criteria needed to be implemented like dimensions, it may not be larger than the motor diameter to not obstructing the air flow. Also its operational temperature range need to be large as it is build onto the motor in warm glass houses. It should survive high voltage impulses on the power line up to several kV as induces by nearby switching high power frequency controllers. Its reliability must me high as it is in use 24/7 for many years.

Production:
A well supported production process provides high quality products. Mounted SMD components require roentgen position checking and PTH mounting require visual and functional tests. After programming the controller various parameters are checked and it is burned-in for 24 hours providing a reliable product with hardly any future drop out.

Global design:
In the early design stages a "Global Design" is made up to satisfy all involved parties. This design including its defined minimal characteristics is the base for the further design.

Schematic diagram:
The global design is further detailed into a schematic diagram also specifying used components, availability and purchase prices. Using this schematic a flow and class diagram is made to assist in the design of the firmware. Required special tooling is defined.

Breadboard:
The first functional design is made on a breadboard to demonstrate is functionality and for testing preliminary software drivers and firmware. A first check with the design goals can be made.

Evaluation:
By using the USB / Bluetooth or WiFi communication port and special developed monitor tools the correct working of of hard- and firmware can be monitored in real-time. Using a suitable GUI interpretation by non IT experts can be made.

Printed circuit board:
When the design is stabilised a double or multi-layer PCB is designed to be used as pre- production model. We pay special attention to the separation of analogue an digital signals, clearances and creepage distances, the Low Voltage Directive and EMC compatibility demands.

Low level firmware:
Part of the firmware is time critical and has a maximum latency of 20 uSec, drivers and frequently used procedures are speed optimised by writing it in assembly language i.e. native microcontroller instructions. The functions are stored in a library for availability to higher level firmware.

Higher level firmware:
Less time critical parts of the firmware, as the operating system, control algorithm, monitor and communication, are written in a higher level language like C, Pascal or Forth. Forth is special as it features a resident operating system, a monitor and is very compact.

High level software:
This is software on users level running on a external computer providing analysis, remote control, data logging, reporting etc, running under Linux, Windows, MacOS or Android. We use Pascal / Delphi, Java of Python to implement these features. Internet presentations are implemented using HTML, CSS and JavaScript.

Communication:
While designing and testing real time access is desired using USB, Bluetooth or WiFi. This is implemented by using plug-in modules on the controller board. Software running on a external computer visualises process variables and allows for modifying control parameters.

Documentation:
The users and operating manual contains a description, schematics and technical specifications. We write these manuals in the English and Dutch language.

CE certification:
In the various stages of development and when the product is finished we check the CE conformity regarding the LVD and EMC compatibility. A LVD and EMC certificate is included.