This is an integrated circuit with a 555 timer circuit is composed of repetitive (also known as two-way double-type timing circuits or timing circuits.) The so-called repeat-type timing circuit which enables refers repeatedly accused of electrical work and stop time, that is, it not only make the charged electrical timing closure, and after closing time can be automatically opened.
  This repetitive timing circuit 555 mainly by an integrated circuit form. It has a simple circuit, stable and reliable, easy to install and so on. In this circuit, which was charged with electrical appliances on and off time can be adjusted, independently of each other, with high practical value.
  Work

Repeat-type timing circuit of the circuit diagram shown in Figure 1 ( click to download schematic diagram ). Figure IC555 and RP1, R1, RP2, R2, VD1, VD2, and composed of a free C1 state circuit, the output side (3 feet) high and low conversion time of the capacitor C1 by the decision to charge and discharge time, the time that are charged with electrical appliances on and off time. Thus, as long as the adjustment of capacitor C1 to charge and discharge time, electrical charges can be achieved by adjusting the time the purpose of opening and closing. In this circuit, the capacitor C1 to charge and discharge time can be adjusted separately and independently of each other, so the added diodes VD1 and VD2.
  The working process of the circuit be summarized as follows: After closing the switch SA, 220V AC voltage by the C5 and R4 (C5 discharge resistance) step-down and VD4, VD5 rectifier and VD6, R3, C3, C4 regulator to provide filtering to the IC555 a more stable DC voltage. SA has just closed, because the voltage across the capacitor C1 is zero and can not be mutated, so the IC at this time of pin is low, pin output high, the relay pull-K, XB was electric socket, charged with electrical start working. At the same time, because IC's pin is high, so the  feet high, the diode conduction VD1, VD2 end, power through the RP1 and R1 to C1, charging rate from RP1 adjustment. When the voltage charge on the C1 to 2 / 3 of the supply voltage (Ucc) when, IC's  pin goes high, the corresponding pin goes low, the release of the relay K1, socket XB loss of electricity, charged electrical appliances stop working. At the same time, due to the IC pin goes low, so the feet will go low, diode VD1 end, VD2 conduction, capacitor C1 through R2, RP2 discharge, discharge rate from RP2 adjustment. The voltage on C1 to 1 / 3 of the supply voltage, IC's feet and goes low, in turn repeat the entire circuit of the working process.

The process of circuit, the IC's feet feet and the voltage change process shown in Figure 2. Which, TH electrical work time for the accused, TL accused of electrical inactivity time. This should be noted that in the first just-machine work, electrical work longer hours than was charged after a rather long working hours, working time is TH + Ts Ts but usually smaller, so the calibration of the entire circuit of the time had little effect.
  Component Selection
  In this circuit, integrated circuit IC can choose NE555, MA555, LM555, 5C1555 other time base circuit; relay K1 can be used at rated voltage between 9V-12V medium power relay, the contacts should be based on the size of the power charged with the size of the selected electrical power; regulator regulator diode VD6 optional value of about 12V, such as 2DW21 etc.; capacitor C5 should be used more than 400V voltage polarity in the capacitor. No special requirements other components, as long as the subject of Figure 1, the parameters can be selected.
  Installation and Commissioning
  The circuit shown in Figure 1, in addition to the potentiometer RP1 and RP2, the other components can be installed on a printed circuit board, the entire circuit is installed and check the power of certainty before debugging.
  Power in the circuit, it should be first transferred to the RP1 and RP2 at the minimum resistance (the resistance is zero), then the relay should continue to pull K and release of the pull and release times respectively by the resistance R1 and R2 value decided by the figure given by the value, the pull and release time is about 5 seconds or so. Such as power, the relay has no pull or suction is not released after the meeting has been, all that there is a fault circuit, this time temporarily with the relays and VD3 IC 3 feet off, and then the voltage with a multimeter measuring 3 feet file voltage, to see whether the high level (about 10V or so) and low (OV) with the ever-changing. If change, then no part of the normal steady-state circuit, fault lies in the relay and protection diodes VD3 on K. 3-pin IC such as the voltage does not change (has been as high or low), then no steady-state part of the circuit is faulty.
  Circuit to work, you can knob in the RP1 and RP2 at the time of calibration. As given in Figure 1, the data selection, the longest time working and resting time was about 60 minutes.