ESP8266 Community Forum

- Mon Jun 03, 2019 6:52 pm #82617 I have found that most sensors have a low power or stand by mode - in many it's simply a case of not talking to them, or sending a power down command. In others it's an enable pin of some sort.

I have found a set of sensors that I can control with either a single GPIO pin tied to all the chip enables, or via software - I haven't needed any external components.

My latest design uses the ISL91107IR buck/boost converter, however I am considering going back to just a straight LDO - my last rev used the NCP186A, which is not in your (awesome!) list:

NCP186
Range voltage: 6 V Max
Max current out: 1 A
Quiescent current: 90 uA
Drop out voltage: 100 mV

Several things have made me rethink using the buck/boost:
- the ESP chip will actually operate at lower than 3.3V. I've heard people using as low as 2.8V to power them successfully. Most of my sensors are already using 1.8V and the ones that aren't can also operate with 3.0V or less
- when the input voltage drops below the threshold on the converter, the boost circuit draws more current to make up the voltage difference. On both solar and battery circuits the increased current draw pulls the supply voltage even lower, so you end up in a death spiral, and the increased current drains the power source even faster.

So in the end, it may work out you get better life by dropping your ESP supply voltage to to 3V or even 2.8V if you can, and using a normal high performance LDO instead.

I need to do some more experimenting...

- Tue Jun 04, 2019 5:55 am #82626

Several things have made me rethink using the buck/boost:
- the ESP chip will actually operate at lower than 3.3V. I've heard people using as low as 2.8V to power them successfully. Most of my sensors are already using 1.8V and the ones that aren't can also operate with 3.0V or less

Just to add to that experience. I was recently checking out the battery state on a door sensor which sends out internet notifications. That had been running fine for over 12 months on a 400mA LIPO using a LDO (xc6203). I was surprised to find the battery down to 2.8V, well into final exhaustion state, but it was still operational. With the drop out the ESP would have been on about 2.6V.

- Tue Jun 04, 2019 7:00 am #82629

In this case do you only power the ESP or power other circuits like sensors, LCD, buzzer, leds, etc.?
When you used only one MCP1700 and did not behave well, were you only feeding ESP or had other things together?

I had one sensor, for detecting tilt/orientation. Plus an OLED display.

- Tue Jun 04, 2019 10:04 am #82637

Several things have made me rethink using the buck/boost:
- the ESP chip will actually operate at lower than 3.3V. I've heard people using as low as 2.8V to power them successfully. Most of my sensors are already using 1.8V and the ones that aren't can also operate with 3.0V or less

Just to add to that experience. I was recently checking out the battery state on a door sensor which sends out internet notifications. That had been running fine for over 12 months on a 400mA LIPO using a LDO (xc6203). I was surprised to find the battery down to 2.8V, well into final exhaustion state, but it was still operational. With the drop out the ESP would have been on about 2.6V.

Thanks for adding your experience! That's even more reason I think I may go back to just an LDO.

I checked the ESP-WROOM02 module that I use and it is officially rated in the data sheet down to 2.7V, and as you said - just about most batteries exhaustion point, so I think it's worth investigating further.