Simple password lock with alarm function

The probe capacitor polarity needle has a head diameter of 5.8. The total length of the 7-pin and 12-pin needles is 5.

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This novel simple password lock with alarm function, the circuit is simple and clear, the function is perfect, not only the confidentiality is strong, but also has the alarm function. The lock can be opened only by turning on the three switches KO, K8, K6 in turn according to the set electronic password. Do not switch on other switches in the middle, otherwise the alarm bell will be energized, and a harsh alarm will be sounded to make the locker smell the wind, or cause the circuit to lock itself, so that the KO, K8, K6 and other effective switches just pressed are pressed. Invalid.

Circuit principle

In the figure below, Kl is the alarm switch. If Kl is pressed, the relay Jl is energized, and the two normally open contacts JIA and JIB are pulled together to make the alarm bell sound. At this time, even if the Kl alarm sound is still large, the alarm can be stopped only after the owner comes off and the power is turned off. KO, K8, and K6 are effective switches. After pressing KO, the J2 relay is energized, the two sets of normally open contacts J2A, J2B are connected; finally, by pressing K6, the J4 relay can be energized, and the J4A, J4B normally open contacts are attracted, thereby turning on the electronic lock power supply smoothly. Open the lock. Note that the opening order of KO, K8, and K6 cannot be reversed, otherwise it is invalid. K2～K5, K7, K9 are normally closed button switches. When opening the lock, you can't press several switches. Otherwise, the circuit is disconnected, and the J2, J3, and J4 relays lose power again. The unlock password set in this circuit diagram is 086. Of course, the reader can also reset the unlock password.

2. Selection of components

Tl is the power transformer, the power is about 2.5W. The primary is 220V/12V, but it is required to work for a long time without heating. VD1 ~ VD4 are silicon rectifier diodes, using 1N4007. Cl is a 47uF electrolytic capacitor and requires a withstand voltage of 16V or more. J1 ~ J4 use DC12V JRX-13F small relay. Because the LD uses a DC 12V FMQ-27 electronic buzzer. KO, Kl, K8, and K6 are normally open buttons. K2, K3, K4, K5, K7, and K9 are normally closed buttons. The models are respectively; LA128-12A new normally open button and normally closed button. The electric control door lock is selected according to the size of the door. Others are subject to the icon, no special requirements.

The KO, Kl, K8, and K6 in the circuit are normally open push button switches. When the circuit is pressed, the other six switches are normally closed push button switches. The normal circuit is turned on, and the circuit is turned off after pressing. DL is a 12V alarm bell; J1 ~ J4 are 4 small relays, the pull-in voltage is 12V, each small relay has two sets of contacts, and JRC6M or JRC5M type relays can be selected.