Current Monitor And Alarm

by R Kambach These circuits are intended for remote monitoring of the cur- rent consumption on the dom- estic mains line. The circuit in Fig. 1 lights the signal lamp upon detecting a mains current consumption of more than 5 mA, and handles currents of several amperes with appropriate diodes fitted in the Di and D2 positions. Tran- sistor T, is switched on when the drop across D,-D2 exceeds a certain level. Diodes from the well-known 1N400x series can be used for currents of up to 1 A, while 1N540x types are rated for up to 3 A. Fuse F, should, of course, be dimen- sioned to suit the particular application. A number of possible transistor types have been stated for use in the T, position. Should you consider using a type not listed, be sure that it can cope with surges up to 700 V. As long as T, does not conduct, the gate of the triac is at mains potential via C, , protective resistor R2 and diode D3 , which keeps C, charged. When T, conducts, alternating current can flow through ...