Pulse Counting

Hi All,

we have a solar generation meter. (Rayleigh Instruments RIHXE12R) Reading the manual it has a pulse counter led also it has a wired output, is it possible to wire this directly to an emonpi?


It should be possible, but the manual is far from clear. You will need to do a basic check.

Using a multimeter, with the leads connected to the pulse output with the polarity shown, check for any indication of a voltage. I would expect that there will be none.
If that is the case, you can connect the pulse terminals to the pulse input of your emonPi.
On the RJ45 I/O connector (the one on the same end as the c.t. jack sockets), connect the meter’s pulse ‘+’ (5) to the RJ45 pin 6 and the meter’s pulse ‘-’ (6) to the RJ45 pin 5. (Coincidentally crossed over, just to be confusing!)


Hi @Robert.Wall

Thanks for your help. it work great.


I’ve got the same meter and was just searching for info on where to stick the pulse meter, but direct wiring seems a better option. I’m a total noob at this (the OEM kit only arrived yesterday!).
Have you got any photos of what you did for direct wiring?
Many thanks

This is our meter for our ASHP which I want to monitor with OEM. I’m not sure where to stick the pulse meter. Presumably on the red flashing LEDs (circled yellow on the photo), but I wondered what the other LEDs are for (circled red).
Although if I can direct wire a connection, I don’t need the led pulse meter anymore.

Welcome, Charles, to OEM.

pulse meter?
I think you mean the optical pulse detector? This: Optical Utility Meter LED Pulse Sensor - Shop | OpenEnergyMonitor

OK, I now see your picture. It’s the yellow-circled one. The others are likely to be for resetting/calibration (and that data will be encrypted!).

I think the printing says “1000 pulses/kWh” - you’ll need that to calibrate it in emonCMS. Check before you cover it up. :wink:

For direct wiring, you’ll need to look for a pair of smallish terminals. They should be clearly marked + and - . You’ll need to unscrew that cover and BEWARE, that will expose live terminals. If you’re at all unsure, post another picture or use the optical sensor.

What did you order?

Is it just to measure this meter?

That’s the one, optical pulse detector.
Many thanks. I’ll look for wiring terminals on the meter and see if it looks straightforward. Otherwise I’ll use the optical pulse detector.

I’ve ordered one emonpi solar PV, plus a emonTx.
The tx is for the ASHP meter. Emonpi going on main consumer unit board to monitor solar energy production.

If I can get all this kit working, next thing I want to look into is a solar diverter for the immersion element (all that hardware is next to ASHP).
ASHP is a nibe f2040 with SM020


The terminals to hardwire are under the screwcover make sure you turn off the power before you open it as it will be live at 240v

If you want to use the pulsecounter use the red led (yellow circle) the red circle is for a handheld device that can read the meter/program it

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great, thanks paul

So I’ve managed to get the EmonPi (solar PV kit) and EmonTx installed. I haven’t had much time to explore it all yet, but it seems to be working correctly. It’s certainly not ‘plug & play’ equipment (not that i was expecting that) but impressive how well it works and how expandable and detailed the system is. I’ve got the EmonTX set up at the ASHP, currently measuring: total power used (CT clip), power used by immersion backup (CT clip), and pulse counting from wired connection on the ASHP electricity meter to RJ45 plugged into the EmonTX.
One thing I’d like to do next is to install some temp sensors (DS18B20). I plan to buy a breakout terminal so I can add multiple temp sensors.
I have a couple of questions:

  1. Can I wire a pulse sensor (either optical, or direct wired from the meter) into the breakout board (emonPi / emonTx RJ45 to Terminal Block Breakout for DS18B20 - Shop | OpenEnergyMonitor) alongside temp sensors? Or is the breakout terminal board only for temp sensors?
  2. I see it’s possible to wire optical pulse sensors to IRQ 1 rather than use the RJ45 connection. The wiring diagram for this show 4 screw terminals. My electricty meter has only a (+) and (-) terminal for pulse sensing. So I’m guessing I need to wire the (+) to screw terminal 4 and the (-) to screw terminal 3 on the IRQ 1. Is this correct? (i checked for any voltage from the electricity meter (+) and (-) pulse output and there was none, so I hope I don’t need any resistors?

Yes, the breakout board is just a number of sockets, the pulse and temperature are on different pins and all pins are paralleled - and the corresponding pins are also paralleled with the screw terminals. (So in fact IRQ1 is on the screw terminals and on pin 6 of the RJ45.) The only difference is the power to the temperature sensors on the screw terminals of the emonTx is switched, it is permanently on for the RJ45 socket for both the emonTx and the emonPi.

That is correct - but the internal pull-up on the pulse input is quite weak, if it doesn’t work, you’ll need to help it with a medium-value resistor between screw terminals 2 (3.3 V) and 4 (IRQ1). The value will depend on what your meter wants - I’d guess anything between 1 kΩ and 10 kΩ would work (the internal pull-up is approx. 40 kΩ).

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Ah, that all makes sense. Thanks Robert.
There isn’t much info on the requirements in manual for the electricity meter (link on first post). Will it be easy to tell if I need to add in a resistor from terminal 2? e.g. will I not get any signal from the electricity meter if the “internal pull-up” is too weak, or could i get missing or bad values?
I’ve got a load of resistors knocking around somewhere.
If i get the resistor wrong, can i do any damage to A) myself, B) electricity meter, C) EmonTX?

Sorry for perhaps daft questions. I’m not any kind of electrical engineer.


You’ll either get no pulses or missing ones.

Probably not yourself. Just maybe the electricity meter, but unless you are using a 5 V USB power supply, the emonTx’s power supply is likely to politely decline and the whole emonTx will stop working before you damage the meter - the emonTx supplies 3.3 V and the meter should accept 5 - 30 V, according to the S0 standard.

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Looking at the output from the pulse counting it looks like i do need to add a resistor as you suggested.
I’ve found the datasheet for the meter which says the pulse output terminals are “S0-Standard DIN 43864” (see attached)
RIHXE12R_Ver_01_2015_04.pdf (747.3 KB). So according to the info on this page: Learn | OpenEnergyMonitor, and what you said, I need to add a 1K Ohm resistor between terminal 2 and 4 on emonTX. So, to double check:
terminal 2-> terminal 4 with resistor,
terminal 3-> -ve meter terminal,
terminal 4 → +ve meter terminal.
Do you think it’s worth trying a 10K resistor first or just bung a 1K in?

That looks about right.

If you have a selection of values, try 10 kΩ and see if it works - it should do, especially if it’s not going any distance (i.e. feet rather than 10s of yards). If it’s not reliable, go to 3.3 kΩ or so, and only end up at 1 kΩ if needed - there’s no point in taking too much current if you don’t need to.

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great, thanks. I’ll try a 10K and see what it gives. I only have 10K and 1K. I guess i could put two or three 1K resistors in series to give me 2K or 3KΩ

Or 2 × 10 kΩ in parallel to give you 5 kΩ. :smiley: