Timing lighting circuit analysis

The timing light can be directly powered by the commercial power 220V, without a power transformer, using only one 555 and one relay, and several resistor capacity components, etc., the structure is simple and easy to install. Suitable for nighttime lighting use, such as corridor lighting. Stair lighting or indoor and outdoor walkways for short periods of time.
The circuit is shown in Figure 27.7. The AN is the start button switch and the D is the light. The 555 operates with a one-shot trigger, and the single-station delay period is the timing illumination period of the illumination lamp.
After pressing, pass the diode 1N4007 half-wave rectification to charge the 220F filter capacitor, establish the DC power supply voltage required for 555 operation 15V. Then 555 second foot potential rises from zero volts, the third pin outputs high level, relay The HG4098 absorbs and connects the power of the lamp D, and the AN switch is replaced by the relay contact switch to form a self-locking state. At this time, the timing lighting starts, and the charging potential of the 555 sixth pin external capacitor (220 μF) rises. When the potential of the 6th pin of 555 rises to two-thirds of the DC power supply voltage, the timing illumination ends, the 3rd pin of 555 becomes the low level, the HG4098 is released, and the lamp D is powered off. At this time, the three electrolytic capacitors enter the discharge state, and the discharge is zero after a few seconds. The timing delay capacitor is preferentially discharged through the 1N4001, so that the timing illumination can be restarted after a few seconds.
It only takes a few tenths of seconds to start the connection time, and there is no problem with manual control.
It can work normally with 15V or 12V. The Zener diode is 15V (0.5W or 1W), and the voltage is limited to 16V or less.
The buck resistor (3.9kΩ) actually consumes about 3.5W during lighting and should be 5W. It can also be used in series with two resistors (2.5W, 2kΩ) or in parallel with two resistors (2.5W, 10kΩ).