ESP8266 Community Forum

- Thu Nov 08, 2018 6:45 am #79070 Hello everyone.

I'm implementing a small IoT project. Basically, I've a small device capable of monitoring the temperature and humidity (DHT22) and if the lights are ON or OFF (basic LDR). The generated data is sent to a local server via WiFi. I'm powering up the NodeMCU with 4 AA batteries, via Vin pin, and both sensors are connected to the 3.3v pin and the output connected to a GPIO pin. The sensor goes to deep sleep and wakes up to do his job. Everything is fine, except the current consumption (around 10 mA in deep sleep), so some decisions must be made and I would love some help.

1- Instead of using the Vin pin, I should use the 3.3v pin by powering up the module with the right voltage, using a LDO MCP1700 voltage regulator, between the batteries and the NodeMCU. Is this the best solution?

2- When the board goes to sleep, it's crucial to have the lowest power consumption as possible. Which is the best MOSFET, that works as a switch, that "cuts" the power from the sensors?

3- I've already cut off the LED in the nodeMCU but I've seen no reduction in the power consumption.

4- Since I'm only using 2 GPIOs, should I switch to the module ESP8266-01 or Wemos D1 mini? My main objective is to get a sensor with a high life cycle (6months to 1 year) so any solution that optimizes my project would be nice .

Thanks for the help.

- Thu Nov 08, 2018 10:55 am #79072 I tried using the MCP1700 and it wasn't reliable. It could not handle the peak currents required.

I have used it successfully by soldering two in parallel. One stacked above the other. I filed down the plastic of the lower one to make it easier to. Two regulators increased the quiescent current but it was pretty low to begin with and I had a series switch so it wasn't a concern. I was stuck with the footprint on the board. I could not use a different pinout part with higher capacity. Now I have been using the HT7833 since it is a 500mA regulator.

- Mon Nov 12, 2018 11:03 am #79108 UPDATE:
- Changed the NODCEMCU to Wemos D1 Mini and the consumption droped, in DeepSleep, to 61uA, increasing the projected life of the 4 AA batteries.

- Still, I haven't tried any MOSFET or Transistor between the sensors and the controller. Any suggestion about the MOSFET to use?

- Regarding the input, I'm powering the Wemos D1 Mini directly with the 4 batteries (Around 6V).

- Wed Nov 14, 2018 5:39 am #79138 just try powering the sensors directly from a gpio pin, the load should be no problem (depending on your LDR setup).