Contactor and outlet surge trigger homemade Iotawatt to reset

I’ve constructed my own Iotawatt using the open-source data provided by the developer, and it has worked well in various scenarios. Recently, I attempted to use Iotawatt with an industrial welding machine equipped with a three-phase contactor in its input. I connected the Iotawatt voltage ports directly to this contactor and attached a current transformer (1:2500) to one of the input phases of the welding machine to measure its current.

Initially, I used a switching power supply for the Iotawatt, but it proved to be susceptible to noise generated by the contactor. The Iotawatt reset almost every time the contactor switched, as indicated by “external reset” entries in the log file.

To mitigate this issue, I switched to a linear power supply, which reduced the vulnerability to contactor activity. While the number of resets decreased, there were still occasional resets occurring when the contactor switched—about one reset event for every 10 contactor switching activities.

After extensive troubleshooting, I observed that when the current transformer (CT) was connected to the Iotawatt, resets occurred due to the contactor switching. Surprisingly, when the CT was not connected to the Iotawatt, there were almost no reset events.

I also noticed similar reset events in home applications. For example, if a device plugged into the same outlet as the Iotawatt was unplugged, the Iotawatt would reset, possibly due to a surge caused by unplugging the device.

It appears that the resets are associated with short, strong pulses that travel through the cable and trigger the Iotawatt to reset. Despite using noise and EMI filters in the input port of the Iotawatt, the issue persists.
At this point, I suspect the problem isn’t originating from the input voltage source. It’s possible that the noise is reaching the ADC ports through the CT (current transformer) and causing the ESP8266 to reset. Considering this, using isolation between the CT and ADCs might be a helpful solution.

Has anyone experienced a similar problem? Any insights or assistance would be greatly appreciated.

I used the device on 220V line. The utilized CT converts a maximum line current of 40 Ampere into 16mA. The nominal current of the welding machine in each phase is around 20 Ampere. So, we have a maximum current of 10 mA in the secondary of the CT when the worker is welding.

There is a push button on the handle of the welding machine. When the worker pushes this button, the contactor switches, and the 3-phase voltage is applied to the welding machine and a 20A current flows through each phase. We connected our iotawatt to the input side of the connector.

The problem with outlet surge is simpler. when an electronic device is pluged in or out from an outlet near the iotawatt, the device gets occasional resets.