Vision protection timer circuit composed of 555

 (1) Introduction to circuit principle Figure 3-12 shows
the vision protection timing circuit. This circuit uses 555 and island, hurricane, threshold
and G to form a pulse generator with variable duty cycle to control
the bidirectional thyristor vs to make the desk lamp EL light up and temporarily
turn off to ensure that the eyes can rest regularly when reading. , thereby protecting eyesight
. The writing desk lamp lights up every 50 minutes and
goes out for 10 minutes. It turns on and off once every 50 minutes .
    (2) Component parameter selection. The selection of components
is shown in Figure 3-12. There are no special requirements. (3) The vision protection timer circuit
    composed of 555 is shown in Figure 3-12.