Pulse Logging of Several Sub Meters

Dave · 17 February 2019 18:58

Hi All
Can anybody recommend hardware that will monitor several water meters (three off) to pass into a EmonPi. The reason for all of the meters is to monitor general hot water and shower cold & hot.
I have a EmonTx nearby but that will only log one meter.

Regards
Dave

Robert.Wall · 17 February 2019 19:19

@pb66 says you can feed the pulse inputs directly into the GPIO of the RPi inside the emonPi - but there’s a practical problem in that you need to get the wires inside the case.

And @dBC recently pointed out that any digital input of the Atmel328P can be used as a pulse input. But again, there’s the problem that spare unused digital inputs aren’t brought out to pins on the emonTx.

franck102 · 18 February 2019 05:41

Hi Dave, I implemented that with an Arduino pro mini and an RFM69, check out this project:

Franck

Dave · 18 February 2019 16:14

Thanks @franck102
I’ve ordered a Arduino board and a RFM69, will let you know how I get on.

Regards
Dave

franck102 · 18 February 2019 18:13

Sound good.

If that is your first project with an RFM69, do remember to keep it away from 5V - in particular if you program the pro mini with a 5V serial adapter you’ll want to disconnect the radio first.
I use coiled spring antennas which gives a good range/footprint compromise; and straight 1/4 wave dipoles when I need more range.

Franck

Bill.Thomson · 18 February 2019 18:35

That would actually be a 1/4 wave monopole.

If you use a groundplane with it, then effectively it’s a dipole, but is still referred to as a monopole.

franck102 · 19 February 2019 06:21

Really? I have a straight wire going up from ANT, and another identical one going down from GND… doesn’t that make it a dipole?

Franck

borpin · 19 February 2019 10:36

There was a long discussion on improving signal here Improving RF signal strength emonTH emonTX

Bill.Thomson · 19 February 2019 13:37

Indeed it does.

If each of your elements is 1/4 wave long, (if not, they should be) then it’s a 1/2 wave dipole.
(you referred to it as a 1/4 wave dipole)

The measurement referring to the antenna wavelength is made from end to end of both
elements vice just one of them.

franck102 · 19 February 2019 20:08

Ah ok, I got the length wrong in my description, the total length is indeed 1/2 wave length:) I learned that from the Arduino forum, and from my empirical trials it has worked much better than ground planes.

With the LowPowerLab library which has transmit power control I can cross the house through two stories at level 4 out of 32, and I’ve had a couple low power setups running for over a year on 2 AA batteries.

Franck

dlmpryor · 20 February 2019 14:21

Build a 12 input pulse counter - multiple input pulse counting
Arduino Pulse counter sketch by Trystan, and tested by Glyn.
Use a serial connection to to your EmonPI

github.com

openenergymonitor/learn/blob/master/view/electricity-monitoring/pulse-counting/12-input-pulse-counting.md

## Build a 12 input pulse counter - multiple input pulse counting

![](files/pulseimg.jpg)

_Pulse counting shield: includes a dedicated barebones Arduino and pull down resistors (detailed below)_

### How it works

We can't use the interrupt method to measure 12 pulse inputs as there are only 2 interrupts on the Arduino. Instead, we need to sample very fast and as continuously as possible in order to catch every pulse and measure the pulse rate accurately. To get best performance we need to:

1.  Read the digital input pins using fast low level digital input register commands
2.  Dedicate the Aduino to pulse counting. e.g. no Ethernet data sending.
3.  Streamline the code as much as possible - e.g. no floating point math and minimal serial printing.

**Low level digital input registers**

When first prototyping the multiple input pulse counter we used the standard Arduino digitalRead to read the state of the digital inputs and we also used the pulse counting Arduino to do other things like sending data via Ethernet. After doing some accuracy tests it quickly became apparent the more inputs we read, the worse the accuracy became. The accuracy deteriorated quite rapidly.

Luckily, we can read digital Inputs much faster using direct port manipulation. It's possible to read a register of 8 digital inputs in one command, although it actually drops to 6 inputs per register due to the use of 2 for serial communication ( 0 and 1) and for the clock crystal (14 and 15).

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