Tag Archives: Home Control 2016 mid-week ramblings

Midweek Ramblings

Following my addition of the BME280 code to Home Control 2016, a couple of guys have suggested they might like to see more accuracy than the integer I use for temperature so I’ve added a new polled value {hightemperature} which is simply the temperature value *10 – but with that extra accuracy – so for example hightemperature mod 10 would give you the decimal point. Not sure I see a need for even higher precision so we’ll leave it at that – personally I just use temperature to the nearest degree.


I’m also playing as you know with port expanders and having already ran out of ports I’ve added an experimental additional 8 port outputs via one of those cheap port expanders I referred to in a previous blog entry.  So assuming this is set to address 38 (typically that’s switch 3 set to off, the others set to on) you can do simply control of out17 to 24, bearing in mind these things start off as inputs floating high.

Port expander

I’ve not attempted at this point to store values in FLASH or preset them on power up – let’s see how much use this gets.

See the Home Control 2016 manual for updates.

On a different tack, this might seem obvious to the hardware guys here and it should have been obvious to me as I’ve been working with electronic hardware since I was old enough to think -  but I made the mistake of getting lazy recently – on my new pergola. I set up on of our boards with a cheap Chinese relay board on GPIO12 – to control a water mister (it gets hot here).  So I would use the timed outputs for example {out12:6,2] which sets output 12 on for 2 minutes before timing out back to OFF state.

I had the water fittings all set to go, got my Imperihome App out, pressed the button and sure enough – excellent misting. I pressed the button to turn the mist off and…. nothing.

I figured a jammed relay – but no. Out of desperation I checked the actual state of the port as set in memory – and it said the output was on – but I’d turned it off – this was impossible. I sat and went through the code over and over – no issues.

I made the classic mistake of assuming the hardware was perfect and it had to be a software issue. In FACT, even though the misting system was kind of isolated from the board by the little external relay board, said relay was powering a 12v washing machine coil – and as it turns out the backlash from the coil was having the weirdest effect on the board – stopping that port turning off – to this day I still can’t explain it as it was actually affecting storage of info in the chip.  I can only assume a voltage spike getting back to the board itself.


I know, sounds daft, so I put a diode across the washing machine solenoid – something I should have done in the first place. Immediately – 100% perfect operation tested over and over. Worth knowing about. See purple diode below.

diode to stop interference

Also added {reset_config} command so that from serial you can reset the board to defaults  - for security this will not work from MQTT.