Scargill

I’m spending some spare time right now working on the home control. My first system is working at home in the UK with a nice little 2-line LCD giving out useful information (as well as accessing that information on the mobile phone of course) but a little while ago we spotted some inexpensive colour LCDs from China – somewhat under £3 each – well you can’t let an offer like that go.

These displays need 5 resistors to work and some software – the library to drive them took some finding and it was originally quite slow but my friend Aidan changed it to work with SPI and I did some more and eventually we got these cheap displays to work perfectly. They look really neat but for some reason my camera just won’t capture the sharp and vibrant colours so you’ll just have to take my word for it. Nice displays.

And so – as of a little while ago – my first working MK2 is ready to go. As well as peak and standby heating control I’ve added a frost setting – up to 255 days hold-off during which time the heating will only come on if the temperature gets below 5c… handy for the cave in Spain perhaps.

The LCD display shows the current humidity, the date, the inside and outside temperatures, the set and fall-back temperatures along with the number of hold-off days.  Below that is the current time (updated every second) and then the dusk and dawn times which are automatically calculated every day. The internal and external temperature displays along with humidity also have trend indicators not shown here.

All working and the phone displays you see are as they appear on my Samsung S4 smartphone…  though I’m not currently actually controlling the heat in Spain but once back in the UK I’ll adapt this to work with the controller in Wark.

The main controller, having moved to the larger 1284 chip – now has all the I/O of the radio slaves and so can function as a stand-alone unit if necessary, simply plugged into the router to give remote control. I played around for a while with adding the display onto the main board but that was slowing things down and ultimately I’ve gone with sending a package out of the serial port so that a separate board, if needed, can handle the display. For my first shot I’ve done a colour LCD board with infra-red remote input – the idea being to add temperature up and down via infra-red for the rental cottage.

I did have 4 fader (PWM) outputs on each of the boards but in the latest update I’ve added a library to both to handle the new serial LEDs – the ones that can be individually programmed and I’ve added commands to change colour and brilliance on these.

The two diagrams below show the main controller utilising a 1284 chip (for extra memory and I/O) which in addition uses a standard Ethernet card and an NRF24L01 radio board…(getting 3v3 from the Ethernet card to feed the NRF)

Below that is a slave board which merely uses a 328 chip and again the NRF24L01 board (with 3v3 regulator onboard) for communications. The master is just cluged on breadboard for now.

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 after this… the April update!