Automatic Load Sensing Power Switch

Part- Total Qty.- Description
C1, C3 -2- 10uF 35V Electrolytic Capacitor
C2 -1- 1uF 35V Electrolytic Capacitor
R1 -1- 0.1 Ohm 10W Resistor
R2 -1- 27K 1/2W Resistor
R3, R4 -1- 1K 1/4W Resistor
R5 -1- 470K 1/4W Resistor
R6 -1- 4.7K 1/2W Resistor
R7 -1- 10K 1/4W Resistor
D1, D2, D4 -3- 1N4004 Rectifier Diode
D3 -1- 1N4744 15V 1 Watt Zener Diode
U1 -1- LM358N Dual Op Amp IC
Q1 -1- 2N3904 NPN Transistor
K1 -1- Relay, 12VDC Coil, 120VAC 10A Contacts
S1 -1- SPST Switch 120AVC, 10A
MISC -1- Board, Wire, Socket For U1, Case, Mains Plug, Socket

Notes



This circuit is designed for 120V operation. For 240V operation, resistors R2 and R6 will need to be changed.

A maximum of 5A can be used as the master unless the wattage of R1 is increased

S1 provides a manual bypass switch.

THis circuit is not isolated from the mains supply. Because of this, you must exercise extreme caution when working around the circuit if it is plugged in.

Source: aaroncake.net