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Flow meter

Hello all,

Is it possible to use a EmonTX V3 to measure (big) water flows? I have already some TX so I want to reuse them if possible.

The requirements of the flow meter:

  • 0-60 L/min and 0 - 180 L/min

Looking forward to your experiences.

I don’t know of a good reason why not. Much depends on the pulse rate and how the pulses are generated - whether by a simple reed switch (that will require debouncing) or by another device (optical or hall sensor) that is probably directly usable.

Assuming 1 pulse per litre, 3 pulses per second is easily accomplished.

I checked some products on ebay and I think that this Flow meter meet my requirements.

I can connect the pulse to DIO 5 and 9?

I can’t find any sensible data about that meter, so I can’t comment. My concerns would be what voltage does the sensor require, and will you need a separate supply and ‘messy’ voltage translation circuits? What current does it draw, and will that imply a second power supply for your emonTx?

It doesn’t specify potable water, so if it is going into a drinking water supply, I’d be concerned on that count too.

Is this of any help?

But that draws 15 mA @ 5 V, so the emonTx would need an external power supply and divider resistors to reduce the output pulse to 3.3 V.

The data at the link posted by the OP says:

Flow range:10-200L/min
Operating Temp:≤80℃,Operating humidity:35%~90%RH
Allow compression:Water pressure 1.75Mpa below
Insulation resistance:>100M OHM
Maximum current:15 mA(DC 5V)
Working voltage range:DC 5V
Storage Temperature:-20~+85℃
Output Waveform:Square Wave,output pulse singal.
ROHS Compliant.
Load capacity:≤10 mA(DC 5V)

Yes, I looked at that. The only doubtful bit is whether the 15 mA includes the 10 mA max load current or not. Either way, it’s no good for the V3 using the ac adapter as a supply, because 5 V isn’t available.

Looks like a new choice of flow meter is in order…

Thanks for thinking along guys! I was thinking that from the point of view of the potable water (as mentioned by Robert) and installation time, a professional industrial solution is maybe better. The screw-dread of the above mentioned flow meter is what I think hard to install on the available tubes. Better to invest in a better meter than in multiple connectors

So I was searching and found a better solution. This Vortex flow meter has a temperature and a flow output from 0.5 to 3.5 V. External power supply isn’t a problem.

Vortex flow meter

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I may be digging old posts but wondering if this has gone further for water monitoring.
I don’t know if this cheap kind of flowmeter has been investigated but I think I may have found a video with the divider resistors you’re referring to
Flow metering with RPi

Are you referring to this:

The simple problem is the meter requires a 5 V supply that’s only available when an external 5 V USB power unit is used, and an output that swings to +5 V will damage the emonTx.
I know exact what resistors might be required, and I don’t watch videos. I was designing electronics many, many years before videos and the Internet existed.

This may be a stupid question but would it be possible to power it externally with batteries for example?
I guess these ones would pose the same issues with a similar load capacity of 10mA - 5V ?

PS: I woud not question your experience nor knowledge, trust me

It does not matter where the 5 V power cones from, so yes, it is possible. Whether it is practical is different. It’s not clear what the quiescent current draw is, clearly the load (the emonTx pulse input) is very low, but there’s no guarantee in which position the meter will stop. You will need a battery (if that’s what you go with) that will give you an acceptable life - 10 Ah will not give you a month if the 15 mA figure is accurate.