The Movement Sensor

It was during the late 1970’s that the Electronics Industry was needing more information from the world around it. Sensors could give electronic circuits the ability to make decisions and respond to changes, thus allowing control of the surroundings. It already had sensors such as Thermostats , Photoelectric cells , Microphones , Switches etc. but there was something missing; a “Human Movement Sensor” which could detect movement within a radius of say 6 metres or more. There were some available but they were large, required excessive energy to operate, costly, and difficult to interpret.

A small , low powered , sensitive , low cost sensor would be ideal for the many applications that awaited its discovery and the time was right to develop one.

The project was difficult and it took 5 years to complete, partly because the critical component, an ultra fast transistor which could turn on and off 5 thousand million times per second had not yet been created. Finally a Dutch company released a 5 Ghz model which was ideal for the job and designing the sensor began. The first prototype required an additional 16 parts and only had a range of 2 metres. Further design modifications were carried out and 5 metres range was obtained, then a eureka moment occurred and I found that 8 of the parts could be eliminated and the range increased to 6 metres along with half the power drawn.