So after some considerable time and loss of sanity I now appear to have a stable setup. I'd like to share what I have done in the hope it may save others a lot of time and frustration.

By enabling debug in the sketches, I eventually realised that I could not get any node to communicate reliably with the gateway. I was getting lots of NACKS even at short distances.

I was sure that the problems were radio related but after trying many NRF24 modules I was about to give up.

Then I read a post somewhere about ground planes.

As a last resort I added a piece of aluminium between my gateway antenna and the radio. (PA/LNA Version). Eureka!! This has pretty much solved the NACK issues.

Following this one or two nodes still intermittently lost contact after a few hours or days. What is strange is that even if moved close to the gateway, errors continue until the gateway is power cycled? I still don't know why this is.

I solved this problem by converting the Node PCB antennas into a dipole antenna as detailed at https://www.instructables.com/id/Enhanced-NRF24L01/.
Now all nodes stay connected.
Now after a couple more weeks of testing all is still good.

I am using Domoticz with the MQTT output passed onto Node Red and now have some really cool things going on.

A big thanks to all that replied and pointed me in the right direction.

@reindier I discovered mysensors while also looking if it was possible to build my own alarm system.
I am pleased to report that it is quite possible if you don't mind the fun of building and fault finding.
I started a few months ago by building some PIR sensors and a serial gateway on a raspberry pi running Domoticz.
From there on I'm slowly adding to the system. I now have notifications for doorbell, outside temperature, solar panel voltage, sensor battery voltages, Sonoff light running Tasmota..... just this week I've swapped over to an ethernet gateway.

All the information is available if you take the time to browse the site. Lots of help on the forum as well.

@skywatch Appreciate the reply. I have made up some 500mA quick blow fuses that I already have from a trusted source.

I have found a workaround by sending the heartbeat message as a separate V_MULTIMETER child. This then gives me a voltage reading of 0V every 30 seconds that I can use with the Domoticz last update feature :grinning:

Would like to hear any better ways of doing this.

Thanks Omemanti

I will check out myscontroller...looks useful.
Ive been playing with openHAB today, and after a bit of a struggle, I've managed to create a virtual switch that sends me an email. This gives me hope that a mysensors PIR node will be able to do the same.
Certainly a great way to learn about many new things!

Here's a quick vid of this morning's project. Getting Alexa to speak the values from the node in my garden.
https://youtu.be/ZcgGLup8iZo

Credit goes to those who made the node red nodes to make it work!

Thanks to all your replies I think I've got it fixed.

I tried another pro mini....still eratic.
I then used that second pro mini and built an identical node on another breadboard. Result was perfect readings.
I then rewired the problematic one and gave it another battery for good measure. It is now more than acceptable although still not as smooth a graph as the second node.
At the moment, running direct from 18650 and not boosting to 5V does not seem to be an issue for the HC-SR501's.
Maybe I will run into problems as the battery voltage lowers.
Node2

Node1

@guillermo-schimmel I have had a look at openHAB but it took me half a day to work out how to get it to send an email. Domoticz seems somewhat easier for a beginner like me. I also like the way it has user accounts built in.

I must say I like the idea of communication with a vacuum cleaner. Maybe I need to get that dust sensor ordered?

@mfalkvidd Thanks for that clarification. I am also thinking of swapping from serial to ethernet when I have time so I can use MQTT.

@mfalkvidd Sounds reasonable. I am thinking a small UPS would be a good idea so I could keep my raspberry pi's, router, switch etc going as well.
Time to look at that relay node then!

@mfalkvidd Good point. You are right I can see a value relating to the battery being sent in the serial monitor.

It is domoticz not updating "last seen" until it sees a "1" from the sensor.

I have my ethernet gateway up and running on a breadboard. It worked first time :sunglasses:

If this is of use to anyone, all I did in Domoticz was go into Setup/Hardware and change the existing serial gateway to "Mysensors Gateway with LAN interface" and press update. All the sensors are then remembered as the Gateway IDX stays the same.

Parts arrived.
Used the default relay sketch. Works great. Nice and loud.

@mfalkvidd That looks just what I'm after...Thanks

I am pleased to say that I have finally got all my sensors and repeater up and running without errors - All battery reports are coming in every 1 or 2 minutes as per my sketch.

The problems were definitely radio related.
Here is what I have done to get it running error free.

1. Start with all the sensors close to the gateway and see if there are any errors.
2. I had one node that was powered with an LM2596 and dropped out after a few hours. Adding in a LC filter has fixed it. Strangely my ethernet gateway is also powered by a LM2596 but is running quite happily. That does however use an amplified NRF24 module on a breakout board.
3. I powered up my repeater again and repositioned the sensors to where I wanted them. I have told the sensors closest to the repeater that they should use that as their parent node.
4. It was unclear on MYSCONTROLLER, if the repeater was being used, but as soon as the repeater is powered down, sensors loose contact so I know it is working.
5. My repeater radio is NRF24L01 with added wire antenna. Much improved range.

@mfalkvidd Thanks for that. Not sure if I worded my question well but I am more concerned that the PCB will take the required components such as 662K so I can still run 3.3 arduino with a LIPO battery. I didn't want to order a stack of them only to find I have missed something!

@mfalkvidd
Thanks that was useful and I went ahead with the sketch shown here: https://www.domoticz.com/forum/viewtopic.php?f=42&t=8039&start=40#p

It works !! :grinning:

@mfalkvidd Thanks for that.

F11 showed that the page was failing to resolve cdnjs.cloudflare.com
I run a pihole so just needed to add to my whitelist.

Fixed. Thanks.

Now back to the node/gateway communication problem!

I've only build build nodes so far using prototype board.

Mostly powered with 18650 lithium and 662K regulator for pro mini 3.3 with regulator and LED removed.
Voltage is measured with resistor divider.
I get great battery life - probably around 2 years.
Simply, will the easy PCB allow my to build this setup?? Looking to save some time.
Thanks

@Yveaux Yes I had manually changed MyConfig.h to reflect the channel number I use. I thought I had read that was the way to do it. Okay thanks for putting me straight. Good to know it was just normal behaviour. I'll add it to each of my sketches in future.
Thanks.