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ESP-12S Inductive Reset

PostPosted: Mon Oct 28, 2019 8:40 pm
by cjohnson355
Been trying to trace down an issue I'm having with a circuit that uses an ESP-12S. I've attached the schematic.

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.


Re: ESP-12S Inductive Reset

PostPosted: Tue Oct 29, 2019 8:58 pm
by rudy
You can try connecting a snubber across the relay contacts. Maybe the contact bounce is causing too much arcing.

I would also use more capacitance across Vcc and ground. I would use at the least 100uF.

You have provided a schematic, but that doesn't show how you have implemented it. How you route/wire the connections can make a significant difference. The schematic could be right but the implementation could have serious problems. There is no way of knowing that from a schematic.

Re: ESP-12S Inductive Reset

PostPosted: Wed Oct 30, 2019 10:21 am
by cjohnson355
Thanks for the reply!

I'll connect a snubber across the relay contacts to see if that fixes the issue.

The project is public on EasyEDA, so here's a link to that: http://EasyEDA.com/johnsoncolb/heater-thermostat

I appreciate the help!

Re: ESP-12S Inductive Reset

PostPosted: Wed Oct 30, 2019 7:43 pm
by rudy
This is not related to your resetting problem. In the future, don't put any metal near the antenna. No traces or external wires, and no copper planes. The copper you have under the antenna will degrade the the sensitivity of the signals. Transmit levels will be worse as well as received signals. It is recommended that the antenna is placed on an edge of the board, I will often have the antenna hanging off the board.

see page 13 of https://www.espressif.com/sites/default ... nes_en.pdf