Circuit and working
The circuit diagram of the security code lock is shown in Fig. 2. The circuit consists of step-down transformer X1, bridge rectifier BR1, 12V voltage regulator LM7812 (IC1), dual-D flip-flop ICs 4013 (IC2 and IC3), rectifier diode 1N4007 (D1), pnp transistor BC557 (T1), npn transistor 2N2219 (T2), 12V single changeover relay RL1, and a few other components.
This project operates with 12V DC which is derived from the 230V AC primary to 15V, 500mA secondary step-down transformer X1. The 230V AC mains is connected to the primary of X1 via CON1 in the circuit. The secondary of X1 is 15V AC, which is connected to bridge rectifier BR1 for rectification and filtered by capacitor C1. The rectified and filtered voltage is then supplied to regulator IC LM7812 (IC1) to regulate it to 12V for enabling the circuit. The glowing LED1 indicates that 12V is available to enable the circuit.
This story is from the August 2023 edition of Electronics For You.
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This story is from the August 2023 edition of Electronics For You.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 9,000+ magazines and newspapers.
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