Greenhouse temperature control circuit

The greenhouse ground heating wire controller circuit consists of a power supply circuit and a heating control circuit, as shown in the figure.
    The power circuit consists of fuse FU, power transformer T, rectifier diodes VD1, VD3, and resistor R. , three-terminal voltage stabilizing integrated circuit IC 1 and
filter capacitor cl.
    The heating control circuit consists of resistors R2~Rs, capacitor C2, Zener diode vs, non-gate Schmitt trigger integrated circuit 1C2 (D1-D3),
JK trigger integrated circuit 1C3 (Al, A2), counting/pulse distribution It is composed of an integrated circuit ICA, a selector switch S, a transistor VI', a thyristor
VTH and a ground wire EH.
    After the AC 2ZOV voltage is stepped down by T and rectified by VDI-VD3, one channel is current-limited by Ri and regulated to +6V by IC1, which serves as
the working power supply for IC2-IC4. The other channel is current-limited by Rz, VTH clamp sampling and IC2. After the internal NOT gate Schmitt trigger Dl is shaped,
the zero-crossing positive pulse of the power supply is obtained, which is used as the clock signal of the internal JK flip-flop Al of IC3, so that the clock pulse output by Al is synchronized with the power supply cycle.
    After the rectified voltage of VD1 is shaped by the C2 delay and the NOT gate Schmitt triggers D2 and D3 inside IC2,
a synchronous positive pulse signal slightly lagging behind the power supply cycle is obtained, which is used as the clock signal for the JK flip-flop A2 inside IC3 ．
    After IC4 performs counting and frequency division processing on the clock pulse output by JK flip-flop Al, it outputs
a high potential in turn from its YO to Y9 terminals in turn.
    S is the cycle ratio selection switch. If S is placed at the YO terminal (1/10 bit), when the first zero-crossing pulse arrives, because the YO terminal of 1C4
outputs a high level and the Yl terminal outputs a low level, when the first power cycle synchronization pulse When the CP terminal of JK flip-flop A2 is added, its Q2 terminal outputs
a high level, causing VT to conduct. VT is triggered and conducts, and the ground wire EH is energized to work. When the synchronization pulse of the second power cycle is added to
the CP lX:j~ of the JK flip-flop A2, the YO terminal of IC4 becomes low level at this time. Yl terminal outputs high level, Q2 terminal of JK flip-flop A2 outputs low level
, VT and VTH are cut off, and EH is powered off to stop heating. That is, when S is placed at YO terminal. The EH only works for 1 cycle out of 10 cycles of alternating current
, and is in the power-off state for 9 cycles.
    If S is placed at the Yl end of IC 4 (position 2/10), then within the 10 cycles of AC power, EH will only be powered on for two of its transition times, and
will not work for eight of its transition times. ,And so on.