Password doorbell alarm

Probe domestic double-head probe 038-BB-5.7L The shape of the two ends of the needle is outside the pointed needle

Photocoupler

As shown in the figure above, the password doorbell alarm circuit. The alarm is composed of a password integrated block IC1, a music integrated chip IC2, a monostable trigger IC3, a police sound integrated chip IC4, a power amplifier, a buck, a voltage stabilizing circuit and the like. The buck regulator circuit provides a +9V DC voltage to the entire circuit. The cryptographic integrated block IC1 uses the RS7225 four-digit cryptographic integrated circuit made by Philips, and its internal logic functional block diagram is shown below. Among them I1~I4 are sequential input selection ends. The external circuit is provided with eight password keys AN1~AN8, among which the four keys are useful password keys, as shown in the figure, which are connected to the corresponding 11, 12, 13, and 14 feet of IC1, the password is "1436", and the other four are It is a bit error key. The order memory inside IC1 is set only when the password is sequentially input to each of I1, I2, I3, and I4. After the match, its 9 feet only output a short pulse. At the same time, the IC18 pin can be flipped from the original low level to the high level only when the "1436" key is sequentially pressed within the limited unlocking time, so that the relay J is pulled in and the contact J1-1 is disconnected. Avoid alarming when opening the door. Correspondingly, the short pulse output of the 1C19 pin triggers the music integrated circuit IC2 (9300) to release a piece of music, telling an acquaintance.
If the password key cannot be correctly pressed within the specified time, or if it is pressed randomly, the IC15 pin outputs a positive pulse with a pulse width of τ=15μs, so that the BG3 tube is turned on instantaneously, and the trigger IC32 pin becomes low level. 555 is set. 3 feet output high level. IC3 and R7, C5 form a monostable delay circuit, the delay time is the alarm time is td = 1.1R7C5, the parameters shown in the figure correspond to about 2 minutes. During the high level of IC3 output (2 minutes), the four analog sound integrated circuit IC4 (KD9561) is applied with voltage, and the output music signal is amplified by BG4, BG5 and bi-amplifier TDA2822M, and the speaker is pushed to give a harsh alarm sound.
If a thief enters the room, the normally closed reed switch Gj will automatically close the two contacts in the permanent magnet ZT due to the door being smashed, and the power supply voltage VDD is added to the clarinet Gj and the resistor R4. The base of BG3 makes BG3 turn on and 555 is set. The high level of the output makes the alarm circuit work, and the alarm sounds. When the owner enters the door. Press the password button correctly to make the IC18 pin output high level. The relay J is pulled in, the contact J1-1 is disconnected, the alarm power is cut off, and no alarm occurs.
In the figure, C2 is a time-limited capacitor. When C2 takes 10μF, the time limit is 12 seconds. The correct operation should be completed within 12 seconds. This circuit has the dual function of doorbell and alarm. Only when the doorbell password is familiar and pressed within a specified time, the bell is reported, and for the "birth" or the door entry, an alarm sounds.