Timing control circuit (3)

(1) Introduction to circuit principle This timing controller can control electrical equipment such as motors and electric heaters to
automatically cut off power after a delayed power-on for a period of time. The timing time is adjustable in 3 levels: 15min, 30min and 60min.
    The timing controller circuit consists of a power supply circuit and a timing control circuit.
    The power circuit consists of the power control button Sl, the normally open contact K1 of the relay K, the step-down capacitor cl, and the bleeder resistor R. , rectifier diode
VDl-VD4, filter capacitor Cz and Zener diode vs. The
    timing control circuit consists of a time base integrated circuit IC, a delay time selection switch S2, and a resistor scale. ~R. , capacitors C3 and C. ,
composed of light-emitting diode LED, relay K and diode VD5.
    Press Sl, the AC 220V voltage is stepped down by C, rectified by VD1~VD4, filtered by C4 and stabilized by vs, to provide +9V (v【,.)
working voltage for 1C. Since the voltage at both ends of C3 cannot change suddenly at the moment of power-on, the ② and ⑥ pins of IC are low level, and the ③ pin of IC outputs high level. Make
K pull in, its normally open contacts Kl and K2 are both closed, the power supply self-locks (after releasing Sl, the power supply remains on), KM pulls in, and the load (electrical equipment such as
motors or electric heaters) works Power on, and l at the same time. ED lights up.
    When placing S2 in the "l" position. _+-9V charges G through Rz, and the delayed power-on time is 15 minutes; when S2 is placed in the "2" position,
+9V voltage charges Cs through the island and hurricane, and the delayed power-on time is 30 minutes; put S2 in the When "3" position. +9V voltage is forbidden ~R. For
G charging, the delayed power-on time is 60 minutes.
    At the end of the set delay power-on time, the voltage of pin ② and pin ⑥ of the IC will rise to 2V [l-/3 (about 6V)), the circuit in the IC will flip, and
the high level of pin ③ will change to low level. K and KM are released, and the working power of the whole machine and load is cut off.
    (2) Component parameter selection
    RL selects 1/2W metal film resistor; Rz-Ra, selects 1/4W carbon film resistor or metal film resistor t
    CJ selects polyester capacitor or polypropylene film (CBB) with a voltage resistance of 400V Capacitors; C2 and G both use aluminum electrolytic capacitors with a withstand voltage of 16V
; G uses monolithic capacitors or polyester capacitors.
    VDl--VD5 all use 1N4007 silicon rectifier diodes.
    vs uses 1W, 9V silicon Zener diode.
    I. ED uses /b5mm green light-emitting diode.
    The IC uses the NE55s time base integrated circuit.
    K chooses JRX-13F type 9V DC relay.
    KM selects an AC contactor with a coil voltage
of 2ZOV, and its contact current capacity should be determined according to the power of the load.     Sl uses AC 220v moving and closing buttons; S2 uses unit three-pole (single pole three throw) transfer switch.
    The selection of other components is shown in Figure 3-47, and there are no special requirements.
    (3) Timing controller circuit (i) is shown in Figure 3-47.