Particle clogging alarm circuit of wheat seeder

Wheat sowing is a matter of great concern to farmers. During the sowing process, they hope to sow evenly and have a bumper harvest next year. However, during the sowing
process, due to particle blockage and the sower does not know it, a section of the seed will be sown empty.
    In order to prevent the above phenomenon from happening, a turtle circuit is used as shown in Figure 8-11. Once particle clogging occurs, the driving mechanism of the seeder turns on
the switch SA, the circuit works, the light-emitting diode emits light, and the photosensitive diode receives light and passes through the capacitor. Cl sends the signal to the 555 timer; the ③ terminal output
is amplified by VT2, VT3, and VT4 to make the speaker sound an alarm, the seeder stops, and the seeding continues after the particle blockage is cleared.