I’ve got this picture in my head of a platform that is low enough power to run for a year on a couple of AA batteries and occasionally wake up and communicate on wifi or Bluetooth LE.
I’m thinking about security or surveillance use eventually but also just to have fun and learn. I’ve never done anything like this before but I do have programming experience and am handy with a multimeter or soldering iron and I would like to tinker, so having a bunch of pins I can hook my own sensors up to. But what draws me to this whole world is talk of sleep power drain in the microAmps so something smart can just run on its own battery.
Yes, there are actually a few devices called watchdog or real-time-clock timers designed specifically for that kind of purpose to be able to send an interrupt and cause your equipment to run at a given point in time so it only running for brief periods of time rather than continually, what kind of platform are you currently using for your project in terms of the microcontroller, and the logic voltage and I’ll see what we’ve got that’s suitable. Have a great day!
Hi Bryce. I haven’t started anything yet, so I don’t have any microcontroller platform currently. I have been considering the ESP32 platform because you get the wifi and bluetooth for free and the chip seems to have some good ultra low power mode built in including ones that wake from RTC or from a sensor. But for real world battery-only usage I figure you’d need to figure out voltage regulation that won’t lose you that efficiency. I was mainly just seeing if there were other platforms that seemed more appropriate. I’m not afraid of things like getting my own USB to serial adapter to program it.
Low power has always been something I have aimed for.
Below is some information from my experience that may help you. Clock Temperature data logger.
Atmega328P, 1000mAH LiPo and charger, RTC, SD card, LED 4 Digit 7 Segment display.
Press button, micro wakes and displays time then temperature.
Also, RTC wakes micro every minute, reads temperature and time and saves to SD card.
When asleep: Atmega328P 20uA, LED 4 Digit 7 Segment display 140uA. (approx)
Runs for about 4 months before needing charge, much longer if LED changed to LCD. Raspberry Pi Zero.
Lowest I got about 90mA, Wifi active about 200mA.
Pretty crappy as a low power device. Adafruit Feather HUZZAH with ESP8266 WiFi and FeatherWing - RTC + SD.
20.6mA in deep sleep mode, HUZZAH 6.4mA, RTC / SD 14.2mA, found design could have been better to reduce power. Without SD card installed 6.4mA, CP2102 USB Bridge on all the time.
Not what I wanted, this was disappointing. Atmega328P.
Lowest power in sleep mode 7uA. But nothing else just push button to wake it Pro Trinket (with Power & Done LEDs removed).
RTC, SD card Temperature sensor. 150uA. (no display)
Anyway, just some of what I have done over the last few years, many other device I have not looked at yet. All the best in your endeavour.
Did you find a low power, radio-equipped platform? This must be a common requirement. I am considering nRF52840 board from Adafruit or Sparkfun. This is a MCU with Bluetooth Low Energy and very low standby current.
Other alternatives would be an ESP32 based board using WiFi or a low power board with a LoRa radio module.
At the moment, I have a bunch of ESP-12F modules which I’ll experiment with. My thought process was that I could use them with a really low powered microcontroller, and power up the wifi module only when I need to transmit something (hold it in shutdown mode otherwise). But I haven’t got around to doing any such experimentation yet - yes I realise this was months ago that I was asking about this!
I did look into other modules that used either 2.4GHz or lower (eg 915Mhz) and my belief is that the ones that don’t have a PA/LNA regardless of frequency would not have enough range/reliability, and the ones that do will not have very different power consumption to a wifi module (if used in this kind of way).
