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Topic: Input Voltage for esp8266/esp32 (Read 20967 times) previous topic - next topic

matt777

Hello,

stupid question here: I read a lot, that the esp8266 can handle 5V as input. So i bought an battery pack, which can handle 3 AAA-batteries and wired this to a micro usb plug. But now, i read that those devices can only handle 3.3V. I also have the new esp32 thing here and with this, i have the same question.

How much voltage is minimum and how much is the maximum? Are 3.3V enough, when i only want to wire an sd card adapter on my esp32 which needs 3.3V?

Wawa

There are many ESP boards. Bare, and with voltage regulators and other supporting parts.
Without knowing which exact ESP board you have, we can't give you the right answer.
Post a link.
Leo..


ElCaron

You can always feed 5V to a usb plug, it must have the necessary circuitry bind it to reduce the voltage. Everything else would be ridiculous, USB IS 5V.
The ESP chip itself will be fried by 5V power supply. It is controversial if the ESP can handle 5V logical input. There are contradicting statements from Espressif. I would not do it, at least not without resistors that would allow clamping diodes to work.

Wawa

All those board have a USB socket, so they have (must have) an onboard 3.3volt regulator.
Without that, you wouldn't be able to connect a 3.3volt ESP to a 5volt USB supply.

The "Thing" from Sparkfun has a LiPo battery connector, and an onboard charger for that.
Why not use that.

Three batteries (3-4.5volt) connected to the USB socket might not be enough for a stable 3.3volt.
The regulator itself could already have a dropout voltage of ~1volt.

Input/output pins are ofcourse NOT 5volt tolerant.
Leo..

matt777

#5
Apr 05, 2017, 08:20 am Last Edit: Apr 05, 2017, 08:26 am by matt777
Thanks for the answer.
With those three batteries, i have 1.5 * 3 volt. I used an multimeter to meassure this at my micro usb plug. I've got there 4.7volt.
I use a LiPo battery on my esp32 Thing, sure (which works fine). But for my esp8266 i use a battery pack.
So, i.e. when i use 10x AAA batteries (10 * 1,5volt) with a micro usb plug, it shouldn't be a big deal because the onboard regulators handle this down to 5volt? I don't destroy my controller?

ElCaron

No, that will be a problem. The regulator will be linear, so it will burn any excess voltage for a given current and get hot from it. You will just use 7-8 batteries to heat your regulator.
A switching regulator would draw less current, but those are not used on those boards.

Also keep in mind that batteries loose voltage when discharging, so especially with rechargeables, you will be at 3x1.2V pretty soon. Since the regulator takes away a minimal voltage, that may not be enough.

Wawa

#7
Apr 05, 2017, 08:56 am Last Edit: Apr 05, 2017, 08:59 am by Wawa
Absolute max regulator input voltage (USB) for the "Thing" is 6.5volt (AP2112 regulator chip).
Four AA batteries "should" work, but very fresh primary batteries could be 1.65volt each...

Not sure about the other ones untill you post/link to their datasheets.
Leo..

matt777

So, lets say i use this micro sd adapter: https://www.roboter-bausatz.de/380/micro-sd-card-reader-adapter-modul-fuer-arduino with the SparkFun ESP32 Thing. My programm will be execute every 10 seconds (just scan for wifis and write the SSIDs on my micro sd card). What would be the best way to power this setup when i want to use this for i.e. 1 month?

ElCaron

#9
Apr 05, 2017, 10:23 am Last Edit: Apr 05, 2017, 10:27 am by ElCaron
Heavily depends on how long that takes. Something between a big phone battery and a car battery.

While powered on, you thingy will draw around 100-300mA. While sleeping, with the right regulator, it will draw around 200µA (if you manage to completely power off the SD-card).
So if it can startup (ESP wakeup is a reboot), scan and write in .1 second. It will need between 1000 and 3000mAh.
If it takes a second and is powered on every 10 seconds, it will need almost tenfold.

In any case, you have to make sure that the quiescent current of your regulator will not drain the battery. A cheap switching regulator (you will need one for a car battery) will draw significant current while the ESP is sleeping. Polulu has efficient alternatives. If using a LiPo, use an LDO like the HT7333 (might be to weak depending on how power hungry the SD card is). The Thing has a suitable one one board.

matt777

Thanks. I will try my luck with those LiPos!

ElCaron

#11
Apr 05, 2017, 10:41 am Last Edit: Apr 05, 2017, 10:41 am by ElCaron
First find out how long one awake cycle takes. It may take quite long, actually. With a Wemos D1 Mini with a battery shield that had to measure a temperature and connect to a wifi to send it via MQTT once an HOUR I got only about two month from a ~1500mAh LiPo.
No I am using my own design with a TP4056 and a HT7333, but don't have enough data yet. It is only running since Sunday and the voltage drop is not significant.
Next step would be replace the Wemos D1 Mini with a D1 Mini Pro with a better antenna, to improve reception and shorten the connect and send phase. But with the Think, you already have an SMA connector for a good antenna.

PolluxProduction

Hi everybody,
i wanted to know if i can power my ESP 32 with the 3,3 V arduinoMega pin.

Paul

ElCaron


suki_kabayasi

Hi everybody,
i wanted to know if i can power my ESP 32 with the 3,3 V arduinoMega pin.

Paul
Yes, using 8 pins in paralel

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