Ic components LM317T production with adjustable manostat, often because potentiometer contact undesirable make output voltage rises, burned load.
If you would like to add a transistor (shown below), under normal circumstances, the base of potential 0 T1 deadlines, the circuit T1 without influence; And when W1 contact undesirable, the base of potential rise T1, when to 0.7 V, electronic component LM317T T1 conduction, will adjust voltage is reduced, output voltage, and also reduce to load protect. If remove triode, disconnect W1 center, 3.8 V small DianZhu attachment, output voltage measurement immediately burned as 21V.
And with a T1, small DianZhu brightness decreases, and now only electronic components LM317T output voltage, thus effectively for the protection of 2V the load.
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