You will design a miniature board with a Wemos D1 compatible pinout, USB charging and programming, and a battery charging circuit. Well that looks like a great board! Small, powerful will also have low power consumption? NO.
Today’s news is about a new development board – Lolin Pico C3. And as I wrote in the introduction. The board itself is very small (25.4×25. 4), it has a ceramic antenna, USB-C charging connector through which Pico C3 is also programmed, on each side an 8-pin rail with power supply and GPIOs (I2C, SPI, ADC etc.) – compatible with Wemos D1, connector for battery connection and integrated charging circuit with current up to 500mA, a dedicated connector for soldering I2C sensors/modules, a voltage divider connected to the battery and ADC and two buttons to switch to bootloader mode – only after switching to bootloader mode can you program the ESP32-C3, which is the engine of this board.
To enter bootloader mode, press the RESET and 9 buttons together.
Connect USB-C to your computer.
Press and hold the button labeled 9.
Press the RESET button and release.
Release Button labeled 9.
And now you should be in bootloader mode.
So where is the problem? As always, the DC regulator. The ESP32-C3 consumption is only 5uA in deepsleep mode – the moment where the ESP32-C3 is completely asleep and only the RTC circuitry works to wake it up.
When you add an LDO with a self-consumption of 40uA (eight times the ESP32-C3’s self-consumption), you’ve killed the whole design.
In fact, there is a ME6211C33 used as a regulator – current delivered up to 500mA, voltage drop 100mV@100mA, typical self-consumption 40uA.
However, such a HT7833 stabilizer has a self-consumption of only 4uA and a voltage drop of 360mV@500mA.
And the difference in price?
ME6211C33 for 0.04USD
HT7833 for 0.24 USD.
And if the price difference is still too big, how about TPL720F33? The manufacturer’s datasheet lists a self-consumption of only 2.8uA (Iout @1mA; 1.8uA @0mA) and a voltage drop of 350mV@400mA. And the price? 0.06USD.
Too bad…
Product page https://www.wemos.cc/en/latest/c3/c3_pico.html
The price of the board on aliexpress is 6.05 USD and shipping is 1.84 USD (dependence on destination country).
