Long time timing circuit composed of 555

(1) Introduction to the circuit principle is shown in Figure 3-6, which is a long-time timing circuit composed of 555
. Press Sl to start timing, adjust RP1 to change the timing time, the timing
range is 3~220min. If the capacitor cI is changed to 2200vF, the timing range can
be 40-48h. The ◎ pin of 555 outputs timing control signal . If this circuit is used to control
a larger power controller, a relay can be connected between B and C or A and B, and
the contacts of the relay can be used to control various timing loads.
    (2) Component parameter selection. The selection of components is shown in Figure 3-6. There are no special
requirements. (3) The long-term timing circuit
    composed of 555 is shown in Figure 3-6.