Thyristor timing circuit controlled by double meter

 (1) Introduction to circuit principle This timer is controlled by two electronic watches with alarm output through thyristors. It can be turned on/off at will, and the
power is cut off once (side) from the power transformer after shutdown. It has no waste, safety, energy saving and high reliability. When using, press SB1, and the power supply
will get 6V DC after being stepped down, rectified and filtered by T, VI)1 and CI . At this time, the power supply makes Kl work through the normally closed contact K-3, the normally open contact Kl-l of XI is closed, and the circuit
is self-locking. At this time, after releasing SB1, the circuit is in working state due to self-locking. When the scheduled power-on audio signal is input from both terminals A and B, it
is rectified and filtered by VD3 and C3 and triggers the thyristor VI'H1, so that K2 is powered to work. K2's normal Open contact K-2 is closed. The socket W is powered and the controlled electrical appliance
is connected. In the same way, when the scheduled shutdown audio signal of another electronic alarm clock enters from C and D, it is rectified and filtered by VD5 and G and triggers
VI'H2t K3 to be powered on, and the normally closed contact K-3 of K3 is released and disconnected. , Kl loses power, so that the normally open contact Kl of Kl is also released and disconnected, and
the entire circuit stops working. Ri is the eye flow resistance, C2 is the starting capacitor of Kl, and VD2, VD4, and VD6 are protection diodes.
    (2) Component parameter selection T uses a small 12V transformer, and the output current should be greater than the sum of the working currents of Kl, K2, and K3. KJ,
K2, and K3 can use 6V small single-pole relays. The contact current of K2 can be determined according to the power of the controlled electrical appliance. Thyristors of tens of milliamperes can be used.
The selection of components is shown in Figure 3-35, and there are no special requirements.
    (3) The thyristor timer circuit controlled by dual meters is shown in Figure 3-35.