I’ve been quite busy lately doing non-Arduino things, like taking a few days out travelling to Germany to see my (almost) 91-year old Mutti (German mum) and brothers and it has given me an opportunity to sit back and think about the way we do things in the Arduino camp.
For example, on the flight back from Stuttgart I thought about the battery saving techniques I’d videoed about on both the Arduino and the ESP8266 platform. It’s all very well getting the Arduino (or whatever your favourite µcontroller is) down to 20µA in sleep mode but what about the rest of “the system”? TFT screens, sensors for the temperature, barometric pressure, rainfall and humidity are just the tip of the iceberg, but they all consume power.
This thinking was brought about by my recent investigation into the Amazon “Dash” buttons. I was intrigued that an inspection of the Amazon “Dash” buttons indicated that they were permanently off until the button is pressed, at which point they spring into action and can determine the difference between a short press, long press and double press. They can also be configured to send out JSON messages to whatever device can receive such messages. Then they switch off. That’s how the little button cell lasts forever!
I’d almost had an (Arduino) lightbulb moment when upon landing in Heathrow, London the armed, British Police boarded the plane and dragged off (not literally) one of the passengers (no, not me). A distraction to my thought processes so I’ve experimented a bit in my workshop – the results of which you’ll see in a future video.
At the very least this means that we can switch on and off everything else whilst putting the Arduino into Deep Sleep. Alternatively, also switch off the Arduino (so current consumption really is zero) as long as there’s a way of switching back on again, via a magnetic door switch, another sensor, an RTC or a simple push button!
Simple is sometimes really the best!
Funny you should post this this weekend. I am right now working on soldering up my own imitation Amazon Dash button inspired by an old video from the great Andreas Speiss (https://www.youtube.com/watch?v=6JD2RMDM88Y)
The schematic for mine can be found in the opening post here https://www.esp8266.com/viewtopic.php?f=160&t=18590
It appears from other posts in that thread that the Amazon Dash button may actually using some kind of deep sleep as it uses a few uA from it’s single AA battery during “standby”. The prototype I have here based on that schematic (but with a Fairchild BS170 in place of the IRLZ44N) uses 0.0uA!
I suspect it would be possible to use a P-Channel FET in the 4.5v line to the regulator with the switch and ESP pulling it low to activate and thus eliminate the opto-coupler but I have no p-channel FET here to test it with.
Incidentally without the opto-coupler the circuit never fully powers down as the ESP finds a parasitic route to ground through the GPIO port and the pull down resistor on the gate.
Hope this is useful for your experiments, Gavin.
sounds great….I look forward to it.
I’m looking forward to this also, I’ll bet that was an upsetting armed police, when your sat there in what is a tube with wings.I wouldn’t like that at all , shows the world we live in, where’s my time machine .I’d be back in the 60’s that for sure.
That sounds like a great concept. Once we devlop a working model there is no longer a need for led flashing to tell us its working. I can’t wait to hear your ideas.