I'm an electronics newbie trying to setup a simple flowmeter on an Arduino.
I have one of those generic 5V flowmeters and I've managed to make it work with an Arduino Nano, following this tutorial https://bc-robotics.com/tutorials/using-a-flow-sensor-with-arduino/.
However, I now need to make this work with an Arduino Nano 33 IoT. I have tried using Adafruit's BSS138 LLC, but I haven't managed to make this work.
My connections are as follows:
Adafruit BSS138 LLC:
LV to 3.3V on Arduino
Lo GND to GND on Arduino
A1 to D2 on Arduino
HV to 5V on Arduino (5V pads bridged on back side)
Hi GND to GND on Arduino
B2 to yellow cable (output) on flowmeter (with pullup resistor to 5V)
Flowmeter:
Red cable to 5V on Arduino
Black cable to GND on Arduino
Unfortunately, this does not work (no serial monitor output). My multimeter shows all voltages are where they should, except for the sensor output which at B2 settles at 0V or 5V when the fan is not spinning, and around 2.5V when it is. I do not own an oscilloscope, so I have no idea how to troubleshoot this.
I could not find a lot of useful info around the webs, so any help is more than welcome!
Can you post a schematic, not a frizzy thing and a link to the sensor showing technical information, not a azon link that just gives sales information.
SPECIFICATIONS
Sensor Type:
Liquid Flow
Typical Input Voltage:
5VDC
Oparating Current: 15mA
Interface:
Analog
Communication Protocol:
Without
SPECIFICATIONS
Working Voltage: 5 to 18VDC
Max current draw: 15mA @ 5V
Working Flow Rate: 1 to 30 Liters/Minute
Working Temperature range: -25 to 80°C
Working Humidity Range: 35%-80% RH
Maximum water pressure: 2.0 MPa
Output duty cycle: 50% +-10%
Output rise time: 0.04us
Output fall time: 0.18us
Flow rate pulse characteristics: Frequency (Hz) = 7.5 * Flow rate (L/min)
Pulses per Liter: 450
Durability: minimum 300,000 cycles
Did you use a pullup with the Nano? I only ask this because it is not usual to use a pullup but it is common practice to use a 1k series resistor.
I'm not familiar with the Nano33, but I'm betting your problem lies with the BSS138. Hall effect flow meters can work on 2.4v, so I wonder if you really need it.
I have tried without the pullup resistor (no luck), but I will also try with it in series.
I also tried with a simple voltage divider, but it did not work.
Perhaps I should change the flowmeter for another model? However, this is the most popular part I could find (no 3V flowmeters found, at all).
but I'm far from sure you should rush out and buy one, and you have not said that you have tried the one you have on 3.3v. You should check the current available on the 3.3v pin though, as it may be better to use a divider on the 5v pin.
I assume your code is kosher, so I think there is something silly going on with the connections, but that definitely does not mean you should rush out and buy an oscilloscope. Just check them.
I will take a SWAG and say the output is an open collector NPN transistor with the emitter grounded. The little data gives states 5V to 18V, so no guarantee it will work below 5V. Try pulling up to 3V3 with a 1K and 5V for the power and measure the output voltage. I think it will always be between 0 and 3.3V. If so you can eliminate the LLC. If it is spinning it will be somewhere in between. Let us Know.
I finally managed to get it to work - it was a programming error and not an electrical one.
I used the DIY ZaidaScope Arduino oscilloscope to troubleshoot my circuit, but found everything to be as expected: 5V PWM signal is correctly lowered to 3.3V, and gets stuck to 0V or 3.3V temporarily, depending on the rotor orientation when it stops spinning.
My mistake was with the interrupt pin (0), which was not one that Arduino Nano IoT 33 supported as an interrupt pin. I changed the interrupt and input pins to 2, and everything started working.
