Controlling one light-emitting diode (LED) with a ESP32 Third is one surprisingly simple task, especially when using the 1k resistor. The load limits one current flowing through a LED, preventing them from melting out http://theengineerstore.in/products/12v-mini-spot-welding-machine-automatic-control-10awg-multiwire-portable-transistor-18650-lithium-battery-spot-welder