I'm using this to control a 5kW heater. The L1 and Heater contact is controlled by the relay in this circuit.
I can't quite trace down what is happening. I've attached a scope to the 12V and 3.3V rail, and when the reset happens the rails are rock solid.
I've tried adding a 100uF electrolytic cap to the VDD and GND pins of the ESP8266, but this didn't help. I have also tried adding a 1100V MOV (all I had) to the relay contacts, but this also did not help.
I have tried having the board 5 feet away from the heater (longer relay contact leads), but this also did not solve the issue.
Here's the really weird part about this whole deal. When it triggers the reboot, the ESP12-S reboots in to a slower clock speed. The WiFi does not work (well it does, but it can't see normal networks), but the rest of the code executes. The Serial, which is always set to 115200 in setup, operates at 77800 baud.
This article describes what state it is in, when it reboots in to this weird state: https://hackaday.com/2019/01/04/undercl ... weirdness/
Anyone have any ideas that I can do to this circuit to resolve this issue? The board will be mounted in the enclosure with the rest of the 240V wiring to the heater.