[ad_1]
The circuit described right here is an digital mixture Safety Code Lock. It opens solely whenever you press 4 keys within the right sequence (known as a code) out of a complete of eight keys put in at your entrance door. In case you press the mistaken key sequence, the circuit resets, and the lock is not going to open. The creator’s prototype is proven in Fig. 1.
Safety Code Lock – Circuit and Working
The circuit diagram of the safety code lock is proven 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 some different elements.
This challenge operates with 12V DC which is derived from the 230V AC main to 15V, 500mA secondary step-down transformer X1. The 230V AC mains is related to the first of X1 by way of CON1 within the circuit. The secondary of X1 is 15V AC, which is related to bridge rectifier BR1 for rectification and filtered by capacitor C1.
The rectified and filtered voltage is then equipped to regulator IC LM7812 (IC1) to control it to 12V for enabling the circuit. The glowing LED1 signifies that 12V is offered to allow the circuit.
The center of this code lock circuit is the CD4013 dual-D flip-flop IC. The clock pins (pins 3 and 11 of IC2 and IC3) of its 4 flip-flops are related to CO1, CO2, CO3, and CO4 factors. The right code sequence for energizing relay RL1 is achieved by clocking within the right sequence, which is the code of the lock. On this case, the code is 8, 2, 6, and 5 (8265).
Subsequently, you could press switches S8, S2, S6, and S5 within the right sequence to open the door. The remaining 4 switches (S1, S3, S4, and S7) are related to the CO5 reset level, which resets all of the flip-flops. By momentarily urgent switches S8, S2, S6, and S5, the clock enter pin goes excessive and alters the state of the flip-flops.
The Q output pin of every flip-flop is wired to the D enter pin of the following flip-flop, whereas the D pin (pin 5) of the primary flip-flop (IC2) is grounded.
The lock code may be modified by altering the connections to the factors CO1, CO2, CO3, and CO4. For instance, if you wish to set the code as 1756, it is best to join the respective swap S1 to CO1, S7 to CO2, S5 to CO3, and S6 to CO4, and join the remainder of the switches, reminiscent of S2, S3, S4, and S8, to the reset level CO5.
Nonetheless, on this challenge, the set code is 8265. Subsequently, the respective switches S8, S2, S6, and S5 are related to CO1 via CO4, and the remaining switches (S1, S3, S4, S7) are related to reset level CO5, as proven within the schematic (Fig. 2).
If the proper clocking sequence is adopted, a low stage (GND) seems on the Q2 output (pin 13) of IC3, which energizes the relay via relay driver transistors T1 and T2. Consequently, the solenoid prompts and the lock opens. The reset keys are related to the set pins 6 via 8 of IC2 and IC3. The facility-on-reset capacitor C2 is used to stabilize the pulses in the course of the power-on of the circuit.
| Components Listing | |
| Semiconductors: | |
| IC1 | – LM7812, 5V voltage regulator |
| IC2 (IC2A-IC2C), | |
| IC3 (IC3A-IC3C) | – 4013 D-flip-flop |
| D1 | – 1N4007 rectifier diode |
| LED1 | – 5mm LED |
| T1 | – BC557 pnp transsitor |
| T2 | – 2N2219 npn transistor |
| Resistors (all 1/4-watt, ±5% carbon): | |
| R1, R7 | – 1-kilo-ohm |
| R2-R6 | – 1-mega-ohm |
| Capacitors: | |
| C1 | – 1000μF, 35V electrolytic |
| C2 | – 100nF ceramic disk |
| Miscellaneous: | |
| CON1-CON3 | – 2-pin connector |
| SV | – 12V solenoid valve |
| RL1 | – 12V, 1C/O (SPDT) relay |
| X1 | – 230V AC main to 15V, 500mA secondary transformer |
Development and Testing
An actual-size, single-side PCB structure for the lock is proven in Fig. 3 and its element structure is proven in Fig. 4. After assembling the circuit on PCB, enclose it in an appropriate field. Repair LED1 and CON1 on the entrance facet of the field, and repair connectors CON2 and CON3 on the rear facet of the field. Use CON2 for connecting the ability provide of the solenoid valve and CON3 for connecting the solenoid valve.
Set up
First, create a 4×4 keypad matrix. Join the respective switches (based mostly on the code lock) to CO1 via CO4 and join the remaining switches to the reset level CO5. Now, set up this keypad on the entrance door and join the solenoid valve to the circuit. Your circuit is now prepared to make use of.
You can too set up this straightforward code lock circuit in your automotive in order that it begins solely when the proper code sequence is entered by way of the keypad. The code lock design will also be utilized in numerous different purposes.
Bonus. You possibly can watch the video of the tutorial of this DIY circuit thought at https://www.electronicsforu.com/videos-slideshows/live-diy-code-
security-lock
Obtain PCB and Part Structure PDFs: click on right here
S.C. Dwivedi is an electronics fanatic and circuit designer at EFY
[ad_2]