Tips to save power

General
1

Dear all,

I am looking for some tips to save power for operating 3.3V/5V sensors on electron. So far, here is what I have tried.

(1) powering a 3.3V sensor from a digital pin (D1)
(2) powering a 5V stepup breakout board from a digital pin (D2) to power two 5V sensors
(3) powering off power source pin (i.e., D1 and D2) after uploading dataset to thingspeak

digitalWrite(power_BME280,LOW);
digitalWrite(power_stepup5V,LOW);

(4) sleeping for 15 mins to save power

System.sleep(WKP, RISING, 15 * 60, SLEEP_NETWORK_STANDBY);

Any comments and suggestions?

I found that 3.3V pin on Electron is always on even it is in sleeping (I guess). Is it normal? Any tutorial about power saving?

Thanks to helping me on saving energy.

2

@changks, a few details need to be added to your powering schemes:

  1. A sensor powered from a digital pin MUST NOT require more than 20ma of operating current.
  2. Power a 5V step-up regulator from a digital pin MUST NOT require more than 20ma! Powering two 5V sensors from a digital pin could easily exceed that limit. Which sensors are you powering?

Powering off the devices will absolutely save you power, as will deep sleeping. The voltage on the 3V3 pin is due to the LiPo battery providing power. The SMT32 processor used in the Electron (and Photon) uses the least power in deep sleep even though power to it remains. The Ublox module of course will continue to consume power, though to a much lesser amount when SLEEP_NETWORK_STANDBY is used.

Some members have done power consumption analysis for the Electron under different modes. You may want to search the forum for those.

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3

For 3.3V sensor, I use Adafruit BME280. It rakes ~1mA or less. In my test, I found that it can be powered by a digital pin, but the air pressure reading is not correct.

For 5V, I used vegetronix VH400 and THERM200. Both of them use < 3mA.

My original intention was that when Electron is on for work then it powers sensor to get readings. Sensors did not need power when the system is in sleep.

If I wire sensors to 3V3 pin, will they use the LiPo battery?! However, sensors don’t need power all the time… That is one thing confusing me.

Thanks

4

In which respect is this thread different from your first one where we established a lot of that already?
Power sensor that requires at least 3.6V

I guess I already answered that in the other thread

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5

Thanks ScruffR. Are there any pins on Electron that offer power only when it is awake?

6

Any of the GPIO pins can be set that way.
As already said too, in deep sleep none of the GPIOs should supply power and when you switch your “power” GPIO to INPUT before entering Stop Mode your semsors will be off too.

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