Modifying a Polycab Wi-Fi Plug
For loads that are perpetually powered-on, it would make sense to switch out the Form A relay with a Form C relay. The relay would then be energized only when the load needs to be disconnected. Two holes need to be drilled in the PCB to allow for the normally-closed contacts.
The primary reason for preferring this behaviour is Tasmota’s Fast Power Cycle Device Recovery feature that can be inadvertently triggered through mains fluctuations and/or instability. With a normally-closed relay instead of a normally-open relay, the load remains powered-on after a reset — instead of waiting until the device configuration is recovered from a backup.
Ideally a Form B relay would be preferred but those are not easy to source in a 29.0mm × 12.7mm package.
The unused normally-open contacts are removed.
Rudimentary insulation with a few layers of pvc electrical tape.
Relay contacts are then bridged with the existing PCB traces.
The completed modification, with adequate clearance.
A secondary reason for this modification was the observation that these Wi-Fi plugs exhibit a build-up of heat after few hours of operation. It was assumed this was because of the relay being constantly energized however the Wi-Fi plugs continue to accumulate heat after this modification.
This suggests that these Wi-Fi plugs were not designed for continuous operation.
The tasmota template for this modification:
{
"NAME":"SLV1910001-NC",
"GPIO":[0,0,0,32,2720,2656,0,0,2624,576,256,0,0,0],
"FLAG":0,
"BASE":18
}