Leassons learned so far:

• I had to add 5V rail since i was unable to get the HC-SR04 to work with 3.3V supply that i use for the ESP.
• The ESP ADC works as fuck. I calibrated it today - since it was givin spoof results for my LM35 temperature sensor.
• Platform.io works nicely to program the device. OTA (over the air flashing) works out of the box. Super!
• If you forget to 'free' malloced buffer you will get the device to reboot with uninformative stack trace
• Boots did happen, sometimes OTA update failed or jammed (causing software watchdog reset) after re-adjusting the power supply and adding capacitors it has at least come very rare.
• Regulators are not suited when trying to get voltage from 12.0 -> 3.3v. They do really heat up with ESP. Like burning hot. Even with heat sink on. I have ordered these "buck converters" that do other than heat with the extra voltage - but shipment from China is not too fast..

Material damage:

• Voltage regulator condensator blew up - inversed connection while doing the 5V rail. Luckily no damage, but huh. I would not expect that much of explosion.
• LM35 was almost destroyed as it was reversed (the specs said BOTTOM not TOP view, uhh.
• Breadboard power supply regulator by feeding 12v input to get 3.3v output. It burned the poor thing.

Figure 1: The ADC values calibrated with potentiometer. UP-DOWN: the value red from analogRead, LEFT-RIGT: The voltage measured with multimeter.