Today, we are going to have a further look on this SwissFlow FlowSensor. Let’s me describe the details or functions for the components inside this project.

Square wave signal, which in between 50Hz and 2000Hz can be detected in the sensor. The measure frequency is divided by 10 and it’s measured in liter/minute.

Assembled flow sensor

The resistor R1 (2K2) is used to accommodate the open collector output of the SF800 to a 5V TTL signal, which available at connector J1.

They used the MM74C925, the Fairchild Semiconductor counter IC. It is a 4-digit counter with seven segment-decoder & multiplexer, plus with the counter & latch registers.

The 7805 regulator is responsible to deliver a stable 5V power supply from the 12V PSU line for the 74C925, the HEF4521 and the CD4093.

Flow sensor PCB

The ULN2003 used for buffering the segment driver output from the 74C925.

It is important to overcome the insufficient power supply problem. So they added T1, T3, T5 (BC547 NPN’s) to saturate the driver transistors T2, T4, T6 (BC327 PNP’s) and this will help to bypass the matter efficiently. [read]

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