Flow sensor

Other Hardware Sensors
1

Hi,

I need to connect a flow sensor to my Arduino Pro Mini 3.3V.
The sensor requires 5V+.
I only have 3.3V power available.
How can I connect the flow sensor to D2 (3.3V)?
Do I need to use a converter or something?

I have the following flow sensor:
Water Flow Sensor - 1 - 60l/min - DN25
Power Supply : 5 - 24VDC
Max Output Current : 15mA @ 5VDC
Pulse Output : Flow = 4.8 * units of flow (L / min) * time (seconds)
Maximum water pressure : < 1.75 MPa
Working Temperature : 0 to 80°C
Material : Plastic
Process Connections : 3/4 Inch

Pin Connections: Red : +5 to 24VDC
Black : Ground
Yellow : Pulsed Output

2

PeterTree:
How can I connect the flow sensor to D2 (3.3V)?
Do I need to use a converter or something?

You don't. It's a signal output, not a power supply.
You really don't have higher voltage elsewhere in your circuit? Then - short of getting a flow sensor that works at 3.3V - the only option you have left is a step-up converter. Of course the input power of the converter does not come out of your Arduino but directly from whatever power source you have available.

Max Output Current : 15mA @ 5VDC

Here is another problem: you can't connect this directly to your Arduino either but this is easier: just put a level shifter in between, and you should be good to go and start counting pulses.

3

Thank you for the reply!

It seems like the level shifter route will be best?

I just realised I need to connect a JSN-SR04T waterproof ultrasonic sensor also (Operating voltage : DC 5V). I have to work with the Mini Pro 3.3V.

Seems like this level converter will work:
https://learn.sparkfun.com/tutorials/using-the-logic-level-converter

4

For connecting the signals, yes, level converter. That does leave you with the question of how to power the sensors.

5

I will use a 5V Step-Up to convert my 3.3V power supply to 5V for sensor.

wvmarle:
For connecting the signals, yes, level converter. That does leave you with the question of how to power the sensors.

6

Much easier to get a 5V Arduino.

7

jremington:
Much easier to get a 5V Arduino.

I know, but I use 3.3V ESP's, 3.3V transceivers and most other sensors I generally use is 3.3V, so I bought a whole bunch of 3.3V Mini Pro's and need to use them :slight_smile:

8

Also easier in this particular situation: use a 5V (or a bit higher) power supply - like a USB adapter - and a regulator to get it down to the 3.3V your Arduino needs.

Another thing: is there anything on the 3.3V Pro Mini that can not handle 5V? After all it's still an ATmega328 processor. Those level shifters may not be necessary. What would happen if you power your Pro Mini at 5V over the Vcc/3.3V pin? That should bypass the regulator.

Can't try that out myself as I only have two 5V Pro Minis, this as I wanted to be able to test stuff at 5V, normally using NodeMCU or ESP12E modules which all operate at 3.3V. Most sensors nowadays indeed operate at lower voltage.

9

It would probably destroy the regulator to power the 3.3V Pro Mini with 5V through the Vcc pin.

However, it is trivial to remove the on board regulator and then power with 5V as above. Just "swipe" the regulator off with a soldering pencil.

I've done this many times for battery powered projects.