Scargill

The home control system is coming along nicely and after a “weekend of code” has some nice new facilities, not the least being a new test desktop PC program and some new radio error checking. Add to that the recent work on week/weekend temperature program and it’s just about ready to roll to both the cottage, our house and Spain. One of the guys helping me has gone off with the first model to play with.

Firstly the Android/IOS App has been tidied up and some new screens put in the place – the first is shown on the left here and shows temperature monitoring, +-adjustments and hold-off (in days) which puts it on standby – useful for the cottage if it’s not in use. Dusk and dawn times are automatically calculated on a daily basis and any of the on-off controls can now include on from dusk until midnight, on from dusk until dawn etc.

The second page shows some demo NRF24L01 remote units and similar on-off controls with these.

The new internal additions allow for momentary radio failure and will temporarily log out and failed unit and it’s siblings to prevent slowing everything down. This was a major pain before as constant polling of units could slow things down. That is all now history.

The third page here can control serial LEDS – the new type with individual serial control. I’ve not yet implemented a simple means to change the lengths of these LED strips but that will come shortly. There’s no reason I can’t store this in EEPROM.

Note the various colour controls and sliders. The very bottom is just an experiment area.

Below right you’ll see the heating controls which allow setting main and fall-back temperatures as well as weekday and weekend timing controls. You should be able to enlarge these images by clicking on them incidentally.

Below all of that is a glimpse of the new PC testing software – just finished working on that and not yet turned it into stand-alone compiled code but that will come this week hopefully. It works perfectly and includes the ability to save profiles for testing different board scenarios.

What has made a bit of a difference is the discovery of the ease of extracting mains control PCBs from some of the low cost plug-in-the-wall Chinese USB supplies – the newer ones have very small boards capable of giving out over 0.5amps at 5v very efficiently.

So now it’s possible to make plug-in-the-wall radio units and masters no longer needing separate power supplies. Added a nominal level of security

Some way to go before I’ll be satisfied with this but it’s starting to look ok. I now have TWITTER alerts kind of running on the larger boards but the low-cost version still won’t have them – I’ve written off to the guy who designed the Ethernet library to see if that can be fixed.

All of this has come a long way from my early experiments with the NRF24L01 radio boards – which seems to have been a popular video https://www.youtube.com/watch?v=VgmVYdSCNLs but documenting this lot could take quite some time.

The only problem with the NRF24L01 boards is range – they are atrocious. Firstly they are very susceptible to noise and many people recommend putting an electrolytic capacitor on the board at the connector. I suspect this has to do with current spikes when transmitting. This does seem to make a difference. Secondly -  they are in the same radio spectrum area as WIFI etc. Thirdly there is no way to gauge incoming signal strength and therefore when used with any mesh network software, it can’t tell which is the best connection to use – and finally – just because of the frequency band they operate in combined with low output, they won’t go through thick walls easily – I’ve seen their range reduced to a few feet in certain circumstances.  On the plus side, they ARE cheap and though they need 3v3 to operate, the data lines happily work with 5v logic – most other cheap boards out there need level convertors which at the very least means a bunch of messy resistors.

On the right you see a little stand-alone Ethernet-driven board which is dirt cheap to put together.. that too has possibilities though of course it still needs an Ethernet lead to run. I’ve sent off for some inexpensive plug-in-the-wall mains USB supplies so I can rip them up and get the supply PCB out of them to power these units.

Somewhat frustrating that they are way too expensive when sourced in the UK but hey, at least they’re available.

That’s it for now, got a lot of work to get through before I can devote more time to this and awaiting feedback from various people to fix some minor library issues… but no doubt about it, the next house will be the one to watch for home automation…

Update July 2014:  I’m in Spain and working with controllers here – the range of the NRF24L01 boards (or lack of it) is getting to be a severe problem. Investigating alternatives such as the Atmel processor with built in radio and some 800Mhz and 433Mhz transceivers.

This all sprang up from my original article on a cottage thermostat in which I envisaged a very simple controller. Then came the UberBareBoard article about an Atmega328-based Arduino clone, initial attempts to master the NRF24L01 radio. The next article was the first item entitled home control and after this – then part 2 and then the winter update – all the time learning more and more. And after this… July and the full mesh.