Inexpensive Occasional Smartsocket + Low-Bandwidth 4G

I’ve recently hit on a problem in which we have an issue with our oil heating back in the UK while we’re spending by far the bulk of our time in Spain.

Despite everything being turned off (hot water off, heating set to OFF – i.e. standby) we discovered thanks to a remote IOT temperature sensor (Sonoff) in the UK kitchen that the heating has been running for 2 months while no-one is there. Thankfully we had UK friends take a look and failing to find anything obviously wrong but confirming the house temperature to be way too high for natural heat, we simply had them pull the plug on the boiler unit based in our rear out-building.

Good idea? Well, no because in a matter of months, as always in winter, it will become very cold in the UK Northeast and a house without any standby heating can soon end up a house with burst pipes not to mention damaging condensation.

So until I can get around to properly sorting out the heating, I need a smartplug solution so I can turn on the heating when needed. Same goes for a dehumidifier. The only problem is that the WIFI in the house simply will not reach out to the out-building which houses the heater – and yes, I’ve tried Powerline adaptors which like WiFi repeaters have proven unreliable. We’re talking very old, very thick solid stone walls.

I was initially pondering, for my UK trip – on hardwiring existing Ethernet through to the far end of the house, then out through the stone wall and into the out-building – that’s a lot of wiring and drilling etc. for somewhere visited only infrequently – and we’re looking at a major tidy up job with cable covers etc. which are far more expensive than the actual (inexpensive) Ethernet cable – not to mention a WiFi access point at the out-building end.

I was chatting to my neighbour in Spain who suggested a MiFi unit – an idea I initially dismissed out of hand – we don’t get a good signal in the UK property (edge of a small village) and cheap MiFi type units aren’t that sensitive – I know that as I’ve tried several ove time and I’m I’m currently using 4G for WiFi using a decent 4G LTE router at the front of both properties (UK and Spain) already. Then there is the ongoing cost of second SIM.

But then things started to come into my head… I don’t need a good signal + high speed data for a second network just to control a couple of smart sockets… and my neighbour kindly loaned me his Huawei MiFi to play with ideas. That’s when I remembered that nearly 3 years ago the company 1nce GmbH (based in Germany) sent me a couple of their 1nce SIMs to play with. The option they sent is a SIM you pay £10 once only for – complete with data – good for 10 years with a TOTAL of 500Mbytes available during that time – at a maximum speed of 1Mbps.

I’d not fully grasped how useful these could be until now and I’ve had one sitting in a drawer since receiving the samples back in 2021 (I gave one away), so I inserted the remaining SIM into the borrowed little HUAWEI E5783B-230 MiFi, plugged the latter into power (it has a rechargeable battery good for 6 hours of power outage) and it runs only slightly luke-warm in my very hot Spanish office so I’m happy to leave it running 24/7 in the UK.

I plugged one of my Sonoff eWeLink smart plugs (S60TPG) into the wall and paired it to the eWeLink APP with my phone connected to the Huawei mobile access point. Instant success – but then I had a moment – I have everything integrated into Home Assistant here in Spain and didn’t want to start messing with a separate APP – once running I took my phone off the access point and back to my normal access point – and that’s when it hit me – for £69 I could buy one of these Huawei units and still have up to 8 years of WiFi available in that SIM as long as I’m VERY careful with how much data I’m consuming.

Between the self-limiting speed on the SIM and the low data requirements of modern Smart sockets I figured I have a solution for my outbuilding without any hassle or wiring. Really, if the data lasts a year that’s better than any normal UK SIM deal by a long way – the cheapest monthly I’ve come across is £5 from GiffGaff. Update: see below, it seems there are quite a few SIM options for IOT use but I’ve not been impressed by any I’ve seen other than 1nce – either nthey could not be bothered to help me get started or at least one said their SIM was not recommended for using in routers. (see related post https://tech.scargill.net/1nce-sims-something-new/)

Meanwhile I realised that because these eWeLink smartplug devices “phone home” – my Spanish Home Assistant integrations are talking to my test smart plug successfully even though it is on a completely different network to the rest of the house. Problem (hopefully) solved. If it turns out the 1nce card data doesn’t last I can always top it up but I’m hoping my guess about data usage is correct.

Up to now this solution wasn’t THAT much cheaper than the wired solution – but as it happens, 3 in the UK use the same model model “MiFi” unit – and there are lots of unlocked units going on UK Ebay – so – I ordered one for £28 + postage (to the UK). Meanwhile, shortly after I arrrived in the UK, the SIM was delivered on time. We’ve just enough time to meet friends and do minimal work on the house so not a lot on researching obscure heating system problems. This is great.

Quick update – we are here in the UK. I WAS going to show you the impressive box the SIM arrived in along with the paperwork – but guess what – someone’s already had a tidy up and this is all that’s left (see photo on the right)…

The reason there’s not much to say about it is that there is no setup – it just works – hooking into whatever 4G provider is available where you are.

Note for complete NOOBS: I generally favour off-cloud home control (Tasmota and similar which, when running on my normal house WIFI can be accessed remotely via Tailscale VPN – not an option with a cheap 4g router such as the Huawei) but in this case, the more typical smart socket is appropriate – control is local but the phone APP and these devices INITIATE conversations via the cloud – handy if you have no fixed public IP address (particularly appropriate when using 4G broadband).

If I were to pick fault in this Huawei and similar inexpensive 4g routers, there no way to install Tailscale (which would simplify Home Assistant integration) – and a BIG ONE – if a power cut lasts longer than 6 hours, the unit defaults to OFF when the power returns. Beware – that’s SUCH A DUMB DESIGN DECISION. I am therefore running mine on an external battery pack (and old type which does not do high speed QC3 and which is therefore useless otherwise but ideal for this situation) and that should protect it from at least a couple of days of no mains power.

Anyway, having convinced myself my Sonoff S60TPG smartplug would work even if I then connected my phone onto another access point, thanks to their phoning home, I then remoted into my Spanish Home Assistant and looked for the S60 device – sure enough – it was in there – thanks to the eWeLink integration I’d previously installed into Home Assistant.

Now why is this latter stage relevant? Why not stick with the eWeLink APP? Well, I possibly could have done – but what I’m after is this… I have a Sonoff temperature sensor in the kitchen in the UK (this is how we knew the heating was stuck on) – as the kitchen temperature was sitting at 30c – I thought the sensor was bust – but no – once we removed the power from the boiler -the temperature returned to what you might expect in the Northeast of England in the summer – maybe 20-25c max instead of over 30c. The sensor was/is working just fine.

As I can monitor the temperature on the main WiFi (which again doesn’t reach the boiler out-building) I can use that (let’s say anything under 6c) to turn on the S60 and hence the boiler until such time as I can get around to fixing whatever the root problem was/is, keeping the heat up regardless – OR I can just use the time of year, i.e. mid-November to late January for example. If you look at most smartplug APPs (including eWeLink and an earlier choice – Shelly) their timers are way too simplistic but Home Assistant is perfectly able to make an automation that will allow very flexible long-term timing control – more flexible even than my own Node-Red-Contrib-Bigtimer.

For now I’ve created a simple HA automation to check for below 6c to turn on the smart switch – above 8c to turn it off.

Here it is for anyone interested – Home Assistant YAML automation – easy to modify – not yet tested…

alias: Control S60TPG-UK Based on Temperature
description: "Turn on S60TPG-UK if Croft Kitchen SNZB-02D Temperature < 6 and turn off S60TPG-UK if Croft Kitchen SNZB-02D Temperature > 8"
trigger:
  - platform: state
    entity_id: sensor.croft_kitchen_snzb_02d_temperature
condition: []
action:
  - choose:
      - conditions:
          - condition: numeric_state
            entity_id: sensor.croft_kitchen_snzb_02d_temperature
            below: 6
        sequence:
          - service: switch.turn_on
            target:
              entity_id: switch.s60tpg_uk
      - conditions:
          - condition: numeric_state
            entity_id: sensor.croft_kitchen_snzb_02d_temperature
            above: 8
        sequence:
          - service: switch.turn_off
            target:
              entity_id: switch.s60tpg_uk
mode: single

Meanwhile I found another SIM (q.beyond) with 1GB data for 10 Euros – but I’ve no experience of this company so can’t vouch for them. It seems there are others geared more toward corporate use…. but I plan to stick with 1nce.

STOP PRESS: I just found another company: Soracom: 59 UK pence a month for 100MB a month. I just spoke to JAMES – one on their sales managers – no extra charges except initial SIM postage (UK, I assume postage in other countries will also be reasonable) – £1.35 non-tracked – £2.70 tracked – and a fee of 1p per megabyte if you go over the self-imposed limit… they have a range of options from 23p a month for 25MB to £8.50 a month for 3GB. You can have the SIM deactivate if it goes over the limit or pay the overage charge – all looks pretty good to me.