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    Thursday 12 January 2017

    Over-Under Voltage Block Circuit With Delay

    Over-Under Voltage Protector Circuit With Delay

    over-under voltage protector circuit with delay

    Components:

    12V step down transformer
    Bridge rectifier diode (DF02M)
    3 Diodes D1, D2, D3 = 1N4001
    Red LED
    6.2V zener diode
    Capacitor: C1 = 1000µF, 35V
    C2 = 100µF, 35V capacitor
    12V DC relay
    Transistor MPS2907A
    3 Op-Amp LM741
    Momentary switch
    Resistors: R1, R5 = 180ohms
    R2 = 200K
    R3 = 50K
    R4 = 47K
    R6 = 1K
    R7 = 1M8
    R8 = 2K7
    R9 = 10K
    Variable resistor VR1 & VR2 = 200K
    Plug
    Socket

    The circuit is a modification to the previous 'Over-Under Voltage Block circuit' with an additional feature. Circuit description and operation is the same except for that added feature which delays the time that this protection device comes up (i.e, supply your load) after the interruption. This feature makes this device an ideal one for electrical appliances that use compressor. Such appliances include fridge, freezer, air conditioner etc

    Delay is determined by the selected value of capacitor C2 and resistor R7. Average delay time here is about 8 minutes.

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