Connections
Puzzle #466
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That just looks like discoloration that sheet metal gets with repeated heating. I would investigate the controls, there are contacts that open/close as a bimetallic strip heats up and cools off (basic thermostat). if the contact are arcing or stuck it could over heat, also since you said smoke was coming from the knob. . .

Depends on the lock being actuated and the torque of the servo, I have some that can do 4.4 N-m.

https://www.amazon.com/high-torque-servo/s?k=high+torque+servo

A stepper motor would also work for sure.

If you have some electronic skill you can use espHome on a esp32 microcontroller to control an RC Servo motor.

https://esphome.io/components/servo.html

If you want out-of-box there are several electronic locks that will work.

https://community.home-assistant.io/t/smart-locks-compatible-with-home-assistant/590662

Strands #195
“Elements of style”
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Connections
Puzzle #458
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Strands #192
“Play-with words”
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I got Hexcodle #397 in 4! Score: 69%

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https://hexcodle.com

Strands #189
“A royal shade”
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It’s half potassium chloride, that can cause you heart issues too if you get to much of it.