I am fairly new to all this and would really appreciate some help :slight_smile:

I have a flowmeter, the Blue-White Digi-Flo F-2000, it’s this version:

Output type - current sinking type hall effect sensor (13.5mA max). Pull-up resistor is recommended. 5k ohm across red & bare wires. Approximately 10 to 350 Hz operating range.

Basically it has a cable with:

RED ? Input Supply Voltage (+ 6 to 24 Vdc)
BARE Signal Output (square wave)
BLACK ? Ground (-)

I would really appreciate info on how to wire it to my Mega with ethernet PoE shield, the idea being I want to power both the Arduino and the flowmeter with PoE.

I also bought a Pololu Adjustable Boost Regulator 4-25V to get the 5v on the Arduino up to a more useful voltage.

Also any tips on the sketch would be much appreciated!

Thanks in advance!


I’m presuming you want to count the number of pulses on the signal output cable.

I have some frequency-counting sketches here:


I presume you want to connect the data wire to one of the timer inputs, (and the ground wire to ground) or possibly just an interrupt input, where the ISR counts pulses, and you just check every second or so how much the count has increased.

What voltage are you getting over the POE? Would that not be in the 6 - 24V range?

Thanks Nick!

It's 802.3AF so I think it is around 48V that goes in to a special part of the PoE version of the ethernet shield that drops it down to something like 7V, my switch sends the voltage directly to the ethernet shield.


If you have 7V you hardly need to take the 5V from the Arduino and boost it back up to 6 - 24V. Just use the 7V. I'm just trying to keep it simple for you.

Thanks again Nick, the problem is I am not sure how to "intercept" and siphon off some of the 7V, its a shield and so it fits on the top of the Mega snugly...

This http://arduino.cc/en/uploads/Main/PoE-datasheet.pdf came soldered on to http://arduino.cc/en/Main/ArduinoEthernetShield making the shield I bought: