Loop timing circuit

This is a practical cycle timing light circuit. After closing the JF switch S, the I-light will automatically light up
for 50min and then turn off for iOmin, and
the cycle will start again and again. It is used as a reading and
writing desk lamp, forcing students to study
for 50 minutes every time. Rest I. min, which is good for
protecting students and improving eyesight.
    The NE555 time base circuit is connected to a
self-excited multivibrator of her type.
After the circuit is powered on, the output terminal ③ pin of the NK555
alternately outputs island level and low level.
    r N
When pin ③ outputs high level, the thyristor VTH is turned on and the lamp E lights up; when pin ③ outputs low
level. VTH is turned off and light E goes out. When the lamp is on, that is, pin ③ outputs high level time Tl:'0. 693
(R: +Rs) (j≈50mln; when the lamp is turned off, that is, pin ③ outputs low level time T2 =0.6i) 3R3 (,. ≈
iOmin. Increase or decrease R., R. The resistance value can adjust the lighting and extinguishing time of the electric lamp . During actual production, a high-resistance potentiometer can also be
connected in series in the capacitor C. charge and discharge circuit to For convenience of use,
a two-pin socket can be used to replace the bulb E of the circuit towel. When in use, just insert the plug of the desk lamp into
the socket of the machine, and the desk lamp becomes a vision protection lamp.