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Hi Andy,

From the information you've provided I have an idea as to what the problem could be. 

Have you read the section on wired pulse counting at the bottom of this page: http://openenergymonitor.org/emon/node/79. The input to the meter/output of emonTx should be 3.3V. The solid-state relay in the water meter should then output a 3.3V pulse and 0V when there is no pulse.

My guess is that 3.3V is a bit low for the solid-state relay in your water meter. Have you got a datasheet for the meter?  The Enica meter probable supplied the meter with a higher voltage (5V?).  This can easily be measured, to find out if what I think is true. This would explain why the system stopped working when the Enica meter was removed. Out of interest how long is the cable run from the meter to the emonTx?

The fix for this problem involves a bit of hack on the emonTX PCB to route 5V to the pulse output socket. This is assuming you are powering the emonTx from a 5V USB supply, its this true? The emonTx has got two positive power rails +3.3V and PWR. The PWR rail is connected directly to the USB/FTDI socket while the 3V power rail is the output from the MCP1702 voltage regulator. In order to route 5V to the emonTx pulse socket you will need to physically break the track on the top the PCB and then solder a wire from the PWR power rail (broken out onto all the JeePort sockets) to the positive terminal on the pulse socket (see image attached below). Unfortunately this hack will make the readings from CT2 and CT3 incorrect and might stop the temperature port working since due to how the PCB is routed they will also now receive 5V when the Atmega is running at 3.3V. The Atmega needs to run at 3.3V since the RFM12B cannot take 5V.  

I plan to incorporate a user selectable jumper in newer versions of the emonTx to allow voltage selection to the pulse socket. 

Let me know how you get on. 

I'll give that a go - thanks. (I'm away from the project at the moment, with limited net access, so will be a week or so before I update)

Can I just verify - should I be able to 'record a pulse' just by making and breaking the circuit between pin 3 (vcc) and pin 2 (IRQ/data) of the pulse plug? (forget any other devices connected).

Hi Andy,

Yes this will work fine. In this case I would leave the resistor R8 in place to pull down the IRQ line. For the firmware Use the emonTx pulse counting example from: https://github.com/openenergymonitor/emonTxFirmware

Good luck, Glyn. 

In that case, there's something wrong.

I wonder if Ive shafted the IRQ line - if I bridge the data to Vcc, its like the circuit is bouncing - instead of 1 pulse, it registers a random value - would I need to generate a 'clean', single pulse to prove this?

Its odd - the rest of the functionality seems ok (although I do get occasional problems uploading sketches) - serial output ok, as is the RF12b to the Nanode.

Anyway, you'll see that Ive sent an email for a couple of new PCB's just in case.

 New PCB's are in the post! RFM12 boards should be here in a week or so.

An easy way to test the puse counting is to use another Arduino or emonTX to generate a simple square wave pulse, try and get it to match the pulse your meter is suppost to be generating. Then connect this square wave to the emonTx puse input and see if it works. If you dont have another Arduino you could use a different digital output on the same emonTx although this might cause some strage timming issues.. 

Might be a good idea to read my post above rearding voltage. I think 3.3V could be a bit low for most meters. Follow the modification in the above post to change this I'm designing an voltage selectable jumper conneciton in for the next version of the emonTx. Proabably available beginning of next year. 

Hope you get to the bottom of the problem.

Good luck.