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I would like to power a Wemos D1 mini with AA batteries for a project.

I'm really new to the subject but as I understood the board runs with 3.3V. You can power the board through the 5V pin because there is a built in dropout there.

To get 5V I thought of using 4 AA batteries (4 x 1.5 = 6V) and mount them with a resistor to lower the voltage to 5V.

What I don't understand is how the resistor is acting on the overall system. Does it increase its lifetime or does it disperse all extra voltage into heat ? In other words, if I use more batteries with bigger resistor, does my circuit gets longer lifetime or should I stick to the required voltage ?

As I understood I could use 3 AA batteries (4.5V) it would work but I would opt for more lifetime if possible (Also I already bought boxes for 4 batteries ;) ).

Is there any best pattern to decrease voltage effectively ? (Diodes, ..., ?).

Thanks

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The Wemos D1 Mini(ESP8266 in general) will use lots of power to keep up with the Wifi. It may go from 80 to 120mA. It wont hurt your device if you use 4 AA battery and can be used direct in the 5V Pin as suggested(not in the 3V3 though).

However, if you are planing to have your project accessing wifi, you should consider implementing deep sleeping. Otherwise you will be changing the batteries every day or every other day. If you dont need the wifi, I would consider other Microcontroller.

That said, it is a good option if you have something that will wake up, do a quick task over wifi and go to sleep. But, I would not use AA batteries in a ESP8266 project if it requires to be on all the time. I would consider 18650 batteries and the charging circuitry to allow you to easily manage the power needs of your project

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  • \$\begingroup\$ Thank you ! I need to access wifi but in large intervals of 12 hours so I do use a deep sleep. I considered using a chargeable battery but because of the use case of my projects it make more sense to use disposable batteries: It's designed for old people and charging that kind of device is not in their habits at all. \$\endgroup\$ Mar 26 at 11:19
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A quick search shows me that the Wemos D1 Mini is an ESP-8266 dev board. According to the manufacturer’s product summary (https://www.wemos.cc/en/latest/d1/d1_mini.html) and schematic (https://www.wemos.cc/en/latest/_static/files/sch_d1_mini_v3.0.0.pdf) it has an operating voltage of 3v3, as well as a 5v input that goes to a 3v3 LDO.

The LDO is an ME6211 (https://stm32-base.org/assets/pdf/regulators/ME6211.pdf) which has an absolute maximum input voltage of 6v5 and whose datasheet (pp. 12-14) indicates smooth and continuous regulation from an input voltage range of ~4-6v.

This means that you can tie four AA batteries directly to the 5v input pin and it will safely power your device over the usable lifetime of your cells. No resistor or other power dissipating component required – and if you were to add one, you would only be hurting your efficiency.

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