@yveaux Some useful info there. Thanks. Will keep an eye on those modules to see if the price drops a bit.

Latest update.

Another 4 boards arrived from ebay. They looked like the bad batch I had in that the tracks on the PCB antenna are slightly thicker.
Sure enough......terrible range.

I have also received the NRF24L01+PA+LNA from the link on the Mysensors store.
This refuses to work in MAX power mode - yes I am using separate 3.3V supply for it. Everything just locks up. Range in other power modes is no better. The printing on the PCB is different to that pictured. Pin 0 is not marked. Confusingly there is a dot next to pin 8 !!!

so so far 3 good radios. 8 Bad ones.

I have asked Banggood if they are still shipping the radios that worked.
Anybody bought any recently that work ok? Maybe time to change to another band?

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

I have now built 3 motion sensors running from a single 18650 and a 3.3V 662K regulator.

I am thinking that I really need a fuse between the 18650 and the board in case anything shorts.

I have discovered the resettable fuses very cheap on Ebay.
https://www.ebay.co.uk/itm/50Pcs-500MA-6V-MT-SMD-Resettable-Fuse-PPTC-PolySwitch-Self-Recovery-Fuses-FY/183334221115

Would these be OK or is there something better?

Thanks

50Pcs 500MA/6V MT SMD Resettable Fuse PPTC PolySwitch Self-Recovery Fuses FY

$1.38

17 available

@wimd Thanks.
Why would I want a non presented node?
I am guessing a Mysensors MQTT gateway will let me send and receive MQTT messages direct to/from the Mysensors network without having to rely on Domoticz?

@affordabletech Have been busy soldering today. Used pro mini with regulator and LED removed + HC-SR501 with regulator and diode removed. 18650 cell for power.
The NRF24 radio us one of the bad ones from with poor range.

On TX it used about 4mA but only 42uA while sleeping.
Battery reporting is working well.

@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!

I would like to build a battery powered siren for alarm activations. There are commercial products that claim a battery life of 3 years.

I have read that for a mysensors node to act as an actuator, it cannot sleep?
I've searched the forum but there is not a lot of info in the past couple of years.
Just wondered if anyone has any tips for what I am trying to achieve.

So far I have ordered this: siren

Wired Mini Siren for Home Security Alarm System Horn Siren 120dB 12V BTSZUK

$2.42

358 available

Update so far:
Still using Domoticz with MS serial gateway, but have installed Mosquitto and in Domoticz I have added "MQTT Client Gateway with LAN interface".
This allows me to control my sonoff over MQTT. Some progress at least.
I notice that all the MySensors data is pushed out on the domoticz/out topic.
So do I really need a MySensors MQTT gateway? I guess that would allow interception if MQTT topics for processing with something such as Node Red.
I have just installed Node Red but have only managed to process some earthquake data (as per the example).

@affordabletech Thanks for the advice.
I have some 3.3V 662K regulators on order. So my plan would be to go from 18650 to regulator and then power everything from that supply.
I have indeed been running a couple of motion test nodes straight from the battery. I started to get some false activations somewhere around 3.6V
I had read that the regulator on the HC-SR501 could either be removed or bypassed, and will look into the possibility of doing this with a jumper.
Yesterday, I removed the LED and regulator from one of my pro minis so hopefully this will reduce power consumption to a minimum.

I use the sleep statement from the standard motion sketch as follows:

sleep(digitalPinToInterrupt(DIGITAL_INPUT_SENSOR), CHANGE, SLEEP_TIME);

Hopefully that is correct?