Electronic password lock six

The electronic code lock described in this example is made of discrete components and is controlled by a 4-digit password and can be used as a power control for door locks or household appliances.
Circuit working principle The electronic code lock circuit consists of power switch SO, power transformer T, rectifier bridge stack UR, relay Kl, K2, password button Sl-Sl2, crystal tube VT, LED VLl, VL2, diode VD1-VD4, resistor R1-R3 and capacitor Cl-C6, as shown in Figure 3-103.

After the AC 220V voltage is stepped down by T, UR rectified and Cl filtered, DC working power is supplied to the circuit.
Turn on the power switch S0, when S1 is pressed, the capacitor C3 is charged; when S2 is pressed, the charge charged by C3 is charged; when S3 is pressed, C5 is charged by the charge on C4; when S4 is pressed, The charge charged on C5 is applied to the gate of VT via R3, which turns VT on, K2 pulls in, the electronic lock is turned on, and VLl and V愧 light up. In practical applications, S154 can be programmed into any set of 4-digit passwords.
In the process of inputting the password, if any button in S5-S12 is pressed incorrectly, the charge stored in capacitors C3, C4, and C5 will be discharged through VD2, VD3, and VD4, respectively, so that relay Kl is sucked, which is often The open contact is turned on, so that Kl is self-locking. At this time, pressing each button in S1-S12 will not work. Only when the power switch SO (should be installed in the concealed place) is disconnected and then turned on, so that Kl can be released, the password can be re-entered to unlock.
Component selection
Rl-R3 uses 1/4W carbon film resistor or metal film resistor.
Cl-C4 selects ultra-small aluminum electrolytic capacitors with a withstand voltage of 16V; C5 uses monolithic capacitors.
VD1-VD4 selects 1N4148 type silicon switch diode for use; VD5 selects type 1N4007 type silicon rectifier diode for use.
VLl and VL2 use a common light-emitting diode of φ5mm.
VT uses lA, lOOV thyristors, such as MCRlO0-6 and other models.
UR selects the rectifier bridge stack of IA and 5OV.
S0 selects ordinary power switch; S1-S12 selects 12 same moving type micro-motion buttons (can also use the standard keyboard of the telephone, the password can be arbitrarily grouped, that is, S1-S4 respectively marked with 4 easy-to-remember numbers as password) .
K1 selects 4098 series gV DC relay; K2 selects l2V DC relay or electronic lock.