In the household are often faced with situations where electrical devices must operate in periodic mode. For example, a heater, a fan. This device can be useful if Your refrigerator stopped off.
The table depending on the work and disconnecting the load (Rn) from the resistances of the resistors R1-R2
The resistance of the resistor Time R1 R2 ON OFF 32K 72K 1 min 24 sec 160K 360K 5 min 2 min 320K 720K 10 min 4 min 480K 1M 15 min 6 min 640K 1,4 M 20 min 8 min 800K 1.8 M 25 min 10 min 960K 2,1 M 30 min 12 min 1.1 M 2.5 M 35 min 14 min
The device operates as follows. When power to the chip U1 begins to charge the capacitor C1, as a result at pin 3 of U1 there is a voltage close to the supply voltage. Upon completion of charging of the capacitor C1 inside the chip U1 to open the transistor, connecting her seventh and first conclusions whereby the capacitor C1 is discharged through resistor R2. After this cycle of operation is repeated.
Uptime and load rejection are presented in the table. Checking it, calculate some other big time not working.
Be sure to attach the triac Q1 to the radiator, for example, U-shaped aluminum plate. The size of the radiator will depend on the capacity of the switched load. The more power, the bigger the radiator.
Author: Vladimir Thalken, LENIN INC, Ukraine; Publication: N. Bolshakov, rf.atnn.ru