This project shows the implementation of a liquid flowmeter using the SF800 flow transducer and the mbed. The Swissflow SF800 directly senses volumetric flow using a simple rotor chopping an IR beam. A hook up diagram is shown below.

The follow connections to the mbed are made:

line 2 connected to Vout pin via a 250 Ohm resistor (Rs)<br> line | connected to Pin 29<br> line 1 connected to to GND pin<br>

Pin 29 and Vout are shorted through 2200 Ohm resistor

The following library and example application can be used to follow the flow rate using the USB serial connection from a PC. The mbed integrates the pulses over a ten second window. Two windows are used and are staggered by 5 seconds to ensure a continuous, noise free, response. Since the counter is not reset the program will presumably crash after a sufficiently long period of time has elapsed due to an overflow. We have not observed this during the timescales over which we are measuring.