@ Valeri V
Hard to troubleshoot the power situation unless every single bit of info is known.
In addition to static voltage measurement, transient power dip in the milli-second level will cause O2 to hang.
Gold rule for power hygiene:
- don't use long cable, or at least, use thick cable
- put a large capacitor as close to the O2 side as possible (I used 470uF 6.3V low ESR capacitor)
- proper use of power regulator IC
Some commonly seen mistakes are
a) use a clone/off-brand/sub-standard IC or that IC has already degraded (due to various conditions)
b) not using the datasheet specified capacitors on its input and output side
< --- many cheap suppliers do that to save its cost
< --- they need to be as close to the IC as possible
c) no or insufficient heat sink and/or heat dissipation (will degrade the IC anyways)
d) use the wrong part (e.g., mis-calculation on drop-out voltage)
- Use improper connection such as DuPont connector and header pins
All of them are basic EE knowledge and are essential for a success project
but some DIY maker Wikis/books failed to mention.