Meteorological stations on.
On reflection, I came to the conclusion that the most expensive and voluminous part of the weather station is the Arduino Uno board. The cheapest replacement option might be the Arduino Pro Mini board. The Arduino Pro Mini comes in four flavors. To solve my problem, a variant with a Mega328P microcontroller and a supply voltage of 5 volts is suitable. But there is also an option for 3.3 volts. How are these options different? Let's figure it out. The fact is that an economical voltage regulator is installed on the Arduino Pro Mini boards. For example, such as the MIC5205 with an output voltage of 5 volts. These 5 volts are fed to the Vcc pin of the Arduino Pro Mini, so the board will be called the "5 Volt Arduino Pro Mini board." And if instead of the MIC5205 microcircuit, another microcircuit with an output voltage of 3.3 volts is supplied, then the board will be called "Arduino Pro Mini board with a supply voltage of 3.3 volts"
The Arduino Pro Mini can draw power from an external unregulated power supply up to 12 volts. This power should be supplied to the RAW pin of the Arduino Pro Mini board. But after reading the datasheet (technical document) for the MIC5205 chip, I saw that the range of power supplied to the Arduino Pro Mini board can be wider. Unless, of course, the board contains the MIC5205 microcircuit.
Datasheet for MIC5205 microcircuit:
The input voltage supplied to the MIC5205 chip can be from 2.5 volts to 16 volts. In this case, the output of the standard switching circuit should have a voltage of about 5 volts without the declared accuracy of 1%. If we use the information from the datasheet: VIN = VOUT + 1V to 16V (Vinput = Voutput + 1V to 16V) and taking Voutput as 5 volts, we get that the supply voltage of the Arduino Pro Mini board supplied to the RAW pin can be from 6 volts to 16 volts at 1% accuracy.
Datasheet for MIC5205 microcircuit:
To power the GY-BMP280-3.3 board for measuring barometric pressure and temperature, I want to use a module with an AMS1117-3.3 microcircuit. The AMS1117 is a linear low dropout voltage regulator.
Photo module with chip AMS1117-3.3:
Datasheets for the AMS1117 microcircuit:
Module diagram with AMS1117-3.3 microcircuit:
I indicated the input voltage from 6.5 volts to 12 volts on the module diagram with the AMS1117-3.3 microcircuit, basing this on the documentation for the AMS1117 microcircuit.
The seller specifies an input voltage of 4.5 volts to 7 volts. Most interestingly, another seller on Aliexpress.com lists a different voltage range - from 4.2 volts to 10 volts.
What's the matter? I think that manufacturers solder capacitors into the input circuits with a maximum allowable voltage lower than the microcircuit parameters allow - 7 volts, 10 volts. And, maybe, they even put defective microcircuits with a limited range of supply voltages. What happens if a 12 volt voltage is applied to a board I bought with an AMS1117-3.3 microcircuit, I do not know.
Perhaps, to improve the reliability of the Chinese board with the AMS1117-3.3 microcircuit, it will be necessary to change the ceramic capacitors to electrolytic tantalum capacitors. This switching scheme is recommended by the manufacturer of the AMS1117A microcircuits, the Minsk plant UE "Plant TRANSISTOR".
