muckmuckmuck
Posts: 9
Joined: Fri Feb 12, 2016 6:22 am

Pulse output water meter

Wed Jun 05, 2019 11:49 pm

Hi, I have an EKM high definition pulse output water meter. From what I can tell, using pigpio is the best method of coutning pulses, via interrupts/callbacks. But I don't how to hook the meter up to my pi. Here is what I know:

Per this thread
, here is some info about my EKM meter:
Black wire - Common
Red wire - Pulse output 1
White wire - Pulse output 2 (Not needed in my case, because I just have one device, my raspberry pi, reading the output, so the white wire will be unused)

Maximum pulse rate is 4.9 pulses per second (which is about 22 gallons per minute, with the model I have)

From an email to their tech support, I also learned:
Up to 24v is acceptable. I specifically asked if 3.3v was acceptable, and they said it is.
Up to 20mA is acceptable.

I've read a lot about pull up and pull down resistors, but I'm still a little unclear about how to wire all this up. I have some breadboards, and a multi pack of resistors of various sizes, but I'm not sure if I have pull up, or pull down resistors (???). I'm hoping someone can lay out a diagram for me to follow.

Thanks!

pcmanbob
Posts: 6193
Joined: Fri May 31, 2013 9:28 pm
Location: Mansfield UK

Re: Pulse output water meter

Thu Jun 06, 2019 7:36 am

Hi.

So what you have stated is a bit confusing , you state its a pulsed output which would imply there is a voltage on the red wire with reference to the ground , but then you say you have been told you can use any voltage up to 24v which would imply the meter has volt free contacts.

Looking at the linked data sheet offers no clue , so you need to find out which it is,

A pulsed output with some voltage measured between red and black wires

or

Volt free contacts that would allow you to use any voltage you choose.
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muckmuckmuck
Posts: 9
Joined: Fri Feb 12, 2016 6:22 am

Re: Pulse output water meter

Thu Jun 06, 2019 7:45 am

pcmanbob wrote:
Thu Jun 06, 2019 7:36 am
Hi.

So what you have stated is a bit confusing , you state its a pulsed output which would imply there is a voltage on the red wire with reference to the ground , but then you say you have been told you can use any voltage up to 24v which would imply the meter has volt free contacts.

Looking at the linked data sheet offers no clue , so you need to find out which it is,

A pulsed output with some voltage measured between red and black wires

or

Volt free contacts that would allow you to use any voltage you choose.
Thanks, my understanding is that it uses any voltage supplied by the pulse reader, but that nothing in the meter is really "powered", it's just opening and closing a circuit, based on a magnetic sensor on a dial (like a clock hand). My understanding was this is common in the pulse output world? I know there are some pulse output devices which use rs485, rs232, etc, but this isn't one of those.

pcmanbob
Posts: 6193
Joined: Fri May 31, 2013 9:28 pm
Location: Mansfield UK

Re: Pulse output water meter

Thu Jun 06, 2019 8:52 am

So its a volt free contact then so you can treat it just like any other switch,

Image

if you want a high on the input when the meter pulses then use the pull down circuit.

if you are only using one output then it should not matter which way round you connect the switch, it would only matter if you want to use both outputs.

if you are not using the second output you should insulate the wire to prevent it shorting out.
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