AC time delay circuit with 555

Posted on Feb 12, 2013

Described timer to participate in the current circuit switch - bulb without any modification of existing pipelines. Connect the timer is in Figure 1 The time switch has only two outlets, which is connected in parallel to the button (Fig. 1a) or switch (Fig. 1b). If you use the button works as a classical staircase circuit switch. Connect a timer switch in parallel to the original, we will extend bulb shines as the time required to leave the room. Dimensions of the timer are so small that it can be installed into standard electrical box under the original power switch. The wiring does not need to change anything, there is no need nor any assistant conductor. The timer is triggered by voltage drop. Switch closes when the interrupt for a moment the power supply which can happen even when a storm or manipulations in the substation. In places where the network is `soft` power matters and executive appliances such as vacuum cleaner.

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Timer scheme is in Figure 2 Resolve power circuit was the hardest nut of the whole structure. The timer must be operated in both closed, and unfastened Triac. If no voltage is present, eg when the terminals A and B shorted out the button, the power is restored after running the timer circuit. If the triac is closed, current passes through the bulb (see Figure 1) to supply and triac and through the bridge rectifier diodes D1, D2, D5 and D6. In place of the D5 and D6 are used in Zener diodes with voltage 5.6 V Zener diode turns in stabilizing the momentary polarity. Voltage drop between terminals A and B is about 7 to 8 in which the brightness of bulbs virtually no impact. The idle circuit is the reactive power flow, passing through the resistor R1 and capacitor C1. The streamlining is now used diodes D3 to D6. The output voltage is stabilized Zenerovými diodes, as well as in the previous case. The filter capacitor C2 is intentionally very low capacity to respond timer for a short press. Zener diodes limit the maximum switching capacity. Power Zener Diode 1N5339 meet the load 398 W. Then, however, each Zener diode loses power almost 5 watts, which is not in a small space dissipate electrical box. Therefore, I recommend not to use a larger ratio than the burden of about 100 W. For higher performance should be possible to replace the D5 and D6 conventional rectifier diodes and output voltage stabilization regulator connected...

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