Current-monitor-and-alarm

The circuit in Fig. 56-lla activates a signal lamp when it detects a line current consumption exceeding 5 mA and can handle currents of several amperes using suitable diodes in the D1 and D2 positions. Transistor T1 is activated when the voltage drop across D1 and D2 surpasses a specific threshold. Diodes from the widely used 1N400x series can accommodate currents up to 1 A, while the 1N540x series is rated for currents up to 3 A. Fuse F1 must be selected based on the specific application. The circuit in Fig. 56-llb functions as a current-triggered alarm. The rectifier bridge formed by diodes D4 through D7 supplies voltage to the relay coil Rel only when the current through D1 and D2 exceeds a predetermined level, allowing series capacitor C1 to pass the alternating main current. The value of capacitor C1 must be chosen to match the sensitivity requirements of the relay coil. This can be achieved by connecting multiple capacitors in parallel until the voltage across the coil is sufficient for reliable relay operation.

The circuit depicted in Fig. 56-lla serves as a current monitoring and signaling device. It is designed to illuminate a signal lamp when the current consumption exceeds 5 mA, indicating that the monitored circuit is active. The diodes D1 and D2 play a crucial role in this circuit, as they must be selected to handle the maximum expected current. The 1N400x series diodes are suitable for applications up to 1 A, while the 1N540x series can accommodate higher currents, up to 3 A. The transistor T1 acts as a switch, turning on when the voltage drop across D1 and D2 reaches the required level, thus triggering the signal lamp.

In Fig. 56-llb, the current-triggered alarm circuit is designed to activate a relay based on the current flowing through diodes D1 and D2. The rectifier bridge composed of diodes D4 through D7 converts the alternating current into direct current, allowing the relay coil Rel to be energized only when the current exceeds a certain threshold. The series capacitor C1 is essential for the operation of this circuit, as it enables the passage of the alternating current to the relay coil. The selection of C1 is critical, as it must be sensitive enough to allow the relay to activate reliably. To achieve the desired capacitance, multiple capacitors can be connected in parallel, which increases the total capacitance until the voltage across the relay coil reaches the operational level required for reliable activation.

Overall, these circuits exemplify the integration of basic electronic components to create functional monitoring and control systems, capable of responding to specific current levels in various applications. Proper selection of components, such as diodes and capacitors, is essential for ensuring reliable operation and performance in the intended environment.The circuit in Fig. 56-lla lights the signal lamp upon detecting a line current consumption of more than 5 mA, and handles currents of several amperes with appropriate diodes fitted in the D1 and D2 positions. Transistor T1 is switched on when the drop across Dl/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 3A.

Fuse F1 should suit the particuiar application. The circuit in Fig. 56-llb is a current-triggered alarm. Rectifier bridge D4 through D7 can only provide the coil voltage for Rel when the current through D1/D2 exceeds a certain level, because then series capacitor C1 passes the alternating main current. Capacitor C1 needs to suit the sensitivity of the relay coil. This is readily effected by connecting capacitors in parallel until the coil voltage is high enough for the relay to operate reliably.

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