My RF24 temp sensors are working well, but for some reason I don't like them. Range is ok but not as good as I expected, the kitchen one occasionally drops out (and that's got a proper antenna rather than an onboard one), even the bedroom one isn't always 100% and that's in the room above the RPi. It's easier to extend a WiFi network than an RF24 network - I've already got an AP at either sides of the house.

That's a good point about the range. I didn't think about that. I don't have any problems where mine are at the mo but last year when I put one outside for a bit it was tricky getting it to connect to my Pi.

If I ignore the deep sleep and running them off batteries, I now have a nice working setup for a plugged in sensor. I think I'll tweak/redesign the PCB now I know what components are sensible and needed and order some.

I'll probably change a few bits to enable multiple power options, maybe add a few jumper points for various options like disconnecting the regulator.

I'm also wondering how easy it would be to add some dip switches to give each module its own unique id rather than programming each one specifically.

It was only the other week that I got my AliExpress "Awaiting Delivery" list down to 0, it is now 20 (fail)

I need to stop buying cheap electronics.

I placed my first aliexpress order yesterday - a lvds cable for my laptop (the one ordered previously rather unsurprisingly didn't turn up and has been refunded via paypal).

I keep adding things to my basket but then chickening out on ordering stuff. So much stuff I want.

Deep sleep now working. Bought a very sharp tip for my soldering iron and managed to get the wire attached.

I've been doing some more testing on batteries to see how long they last in various setups. All submit a temperature every minute(ish).

3xAA NiMH (no regulator)
No sleep modes
27 hours

4xAA NiMH with AMS1117-3v3 regulator
Small solar panel to attempt to charge the batteries
No sleep modes
58 hours

3xAA NiMH (no regulator)
Deep sleep for around 50-55 seconds (can't remember exactly)
Still alive and approaching 72 hours

Next will be deep sleep + solar panel, and possibly remove the power LED.

Definitely cut the power LED. That alone will probably run the batteries flat fairly quickly. How reliable is it waking from sleep?

Probably not an issue for you if you're going to switch to WiFi sensors but with the RF24s you can route the signal through another close radio to get better range. Not if the middle one is sleeping though.

I read there were issues waking from sleep, but so far I'm at about 86 hours, which means around 5160 successful sleep/wake cycles.

Voltage has levelled off at about 3.6V which is probably close to the minimum the AA batteries can put out.



Error
Voltage
Temperature

3xAA NiMH (no regulator)
Deep sleep for around 50-55 seconds (can't remember exactly)
100 hours

Assuming it has actually died overnight and not just failed to wake from deep sleep (which I guess could be considered the same thing, it's in a coma!)

Can you wake it to do stuff without turning the WiFi on?

4 days. I wonder how much difference the power led would make to the time.

And what do you use to make your graphs?

Flot - www.flotcharts.org

Everything goes in to a MySQL database, then it's PHP + Flot to do the charts.

I think you can do plenty of stuff without turning the WiFi on, there's specific commands in the sketch for the WiFi so I imagine you could wrap them in some sort of if/else to decide whether you want the WiFi to be used.

4xAA NiMH
Regulator
Solar Panel
Deep sleep for around 50-55 seconds (LED still connected).
Currently at 150 Hours.

This one may actually last forever.

*forever being until last night

Have a look at this. Some info on running those things on a battery. http://blog.hekkers.net/2015/04/06/esp8266-good-enough-for-a-battery-powered-sensor/

My sensors have been running for 5 months and still going strong.

My problem is that I'm reporting the temperature every minute, which I won't be changing, so I'll never get a year off just a battery.

Some Lithium battery charging boards arrived yesterday for me to charge some 18650s pulled from a laptop battery. I also discovered a new version the same day I ordered which also have discharge protection for unprotected cells, so I'm waiting for them to arrive then I'll have a setup which will be...
 

Solar Panel
     |
Charging/Protection Board -> ESP8266
     |
18650 cell

"I'm reporting the temperature every minute"

Why?

The "system" controls my central heating so I like the "thermostat" readings to be fairly regular so it turns on/off when it needs to.

This doesn't cause it to turn on/off much more frequently, increasing wear and tear?

You could check it every minute but only send the temp if it's changed from the last check.