Single button digital circuit dimmer light circuit

The single-key digital circuit dimmer circuit is shown in Figure 42. It uses CD4017 digital circuit and single-junction
transistor to form the trigger circuit of the finished thyristor. It has adjustable brightness with a leaf stop and is very convenient to use.
    The mains power is stepped down by the transformer r, and then goes through the luminous tube LED, the voltage regulator tube vs. the voltage regulator to output the
DC voltage around SV, which is used by CD, I017 and single junction tube vu. I.ED also serves as the power supply working instruction. lamp.
LD4017 forms a pulse with seven rising edge triggers, which can make the QO-Q9 terminals output high-level "1" in sequence. Pressing the button
Si{ once is equivalent to inputting a trigger pulse to CDI017, causing the high-power half-end of the input terminal Q(J-Q9) to move forward
by one . If at this time, the Q2 terminal outputs a high level "l", and the other ports are all low level ".", the high level output by the state Q? terminal
is charged to the capacitor c" by R; (11k), causing the (j terminal voltage to rise. When it rises to
the fold of the single-junction transistor V¨ When the voltage changes, vU is turned on, (1: discharges to R,, forming a trigger pulse to
block the thyristor VTH. When the alternating current crosses zero, VTH is turned off, (,.) and the power supply starts again, so VTfHl remains constant. The conduction angle of
bulb E is at a certain brightness. When further light is required, press -FS[+ and input a
trigger pulse to (; D4017 , the high level of its output terminal moves forward one bit, that is, Q3 output r Level "1", other output terminals are all low
level ".". At this time, Q3 outputs high level and interprets R. to charge (,. Since the resistance of R. is 9 1kC/, which is smaller than R,,
so e The charging rate speeds up, that is, the conduction angle of VTH moves forward, and the brightness of the light increases by one level. Press
SH repeatedly to make the QO-Q9 Rui output high-level "1" in sequence, and QO-Q9 continuously cycles to adjust the brightness of the light.