You're using a step-down converter with what looks like a LM2596 or something similar.
Can you try the setup with only the Dallas units connected on a different power supply?
For example start with powering it via USB or some lab power supply, or move the switching power supply away from the long wires of the Dallas units.
A switching power supply may produce high frequency noise which can be picked up on long wires.
Yes this is a LM2593, do you have a better recommendation?
I had the ESP with 3 Dallas sensors on the USB port and supplied it with 3.3V,
no problem. With a fourth sensor, the data stopped sporadically.
Just another note.
Since you're using long cables, you may want to power the Dallas sensors on 5V but connect the pull-up resistor to 3v3, like discussed here:
https://www.raspberrypi.org/forums/view ... 6#p1468562
I have now exchanged the cables, 3 sensors, cable ~ 15 m, 3x1.5mm2, 5V + 4.7kOhm, with level shifter.
Is currently running stable
I do have a setup here on my bench running for months now with 12 of the cheapest Dallas sensors I could find (thus very likely not genuine parts) and those run very stable for months.
So I guess it is probably something related to external noise, bad contacts or unstable power supply. (voltage drop when switching a relay using thin wires carrying power for example)
Which cable cross-section do you use in your own setup?