Electronic code lock nine

This example introduces a light-controlled electronic code lock, which uses an infrared sensor for light-controlled encoding and a special key (a card with a fixed hole) for decoding. When the key used is correct, the electronic code lock can be opened normally; if the key used is incorrect, the electronic code lock cannot be opened and the alarm will sound. The device can be used in homes or warehouses, safes, and other places.
Circuit Working Principle
The electronic password lock circuit consists of a light-controlled encoding circuit, a logic control circuit, a control execution circuit and an alarm, as shown in Figure 3-106.

The light control encoding circuit is composed of infrared light-emitting diodes VLl-VM, infrared receiving photodiodes VDl-VD4 and resistors Rl-R8.
The logic control circuit is composed of a NAND gate integrated circuit ICl (Dl. D4) and an OR gate integrated circuit IC2 (D5-D7).
The control execution circuit is composed of transistor V, resistor R9, diode VD5 and relay K.
The alarm circuit is composed of voice integrated circuit IC3, audio power amplifier integrated circuit IC4, Zener diode VS, resistors RlO-R14, capacitor Cl-C6 and speaker BL.
Normally, VD1-VD4 are illuminated by the infrared light emitted by VLI-VM, the output terminals of NOR gate D7 and the output terminals of NOT gate D4 are both low level, V is cut off, K is in the released state, and the electronic code lock is in the locked state; The alarm does not sound, and the circuit is in a waiting state.
When unlocking, after inserting the card key into the keyhole, the infrared rays emitted by VLl and VL2 shine on VDl and VD2 respectively through the two holes on the key, while the infrared rays emitted by VL3 and VLA are blocked by the card key, and the logic control circuit After the voltage signals at both ends of VDl-VD4 are processed by logical operations, D7 outputs a high level, V is turned on, and K is closed. Its normally open contact turns on the working power of the electromagnet (the circuit is shown at the end), and the lock be opened. At this time, because D4 still outputs low level, the alarm does not work.
If an invalid key is used to unlock the lock, the output terminal of D7 remains low, and the output terminal of D4 outputs high level. IC3 is triggered to work, and its 4-pin outputs the voice signal of "Catch the thief". After the electrical signal is amplified by IC4, it drives the speaker BL to emit a loud voice alarm sound.
Component selection
Rl-R14 uses 1/4W carbon film resistor or metal film resistor.
Cl, C3, C5 and C6 all use aluminum electrolytic capacitors with a withstand voltage of 16V; C2 uses high-frequency ceramic capacitors; C4 uses polyester capacitors.
VDl-VD4 all use PH302 infrared photodiodes; VD5 uses lN4007 silicon rectifier diodes.
VL1-VM all use TLNll0 type infrared light-emitting diodes.
VS uses 1/2W, 3V silicon Zener diode.
V selects C8050 or S8050, 3DG8050 silicon NPN transistor.
ICl selects CD4011 four-NAND gate integrated circuit; IC2 selects CD4001 four-NOR gate integrated circuit; IC3 selects LH168B or LQ-46 and other models of voice integrated circuits that store the "Catch the Thief" voice message; IC4 selects LM386 type Audio power amplifier integrated circuit.
K chooses 9VB DC relay.
BL uses lW, 8Ω electric speakers.