Electronic combination lock 2011-03-10

ElectroMaster submitted a new article:

Electronic Combination Lock - This circuit is very basic to build. To open a the lock which is connected to the K1 Load you must

This circuit is very basic to build. To open a the lock which is connected to the K1 Load you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1,S2,S3,S4. If any of the other switchs are pressed the circuit will reset and you will need to start over. Depending on how you wire the switchs, you can use any 4 switch combination.

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if dis is a competition can i get details

what is the use of s5,s6,s7 & s8???

ananthnagbme said:

what is the use of s5,s6,s7 & s8???

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s5, s6, s7, and s8 reset the chips, as mentioned in the description. This makes it harder for the code to be hacked, as it resets the whole thing if just one wrong key is pressed.
Der Strom

The basic idea is very good.

However, part of the circuit is missing, so I can't see how the circuit resets after the lock is enabled. Nor can I see what the supply voltage (Vs) is.

The 100k resistors could be replaced with short circuits & I would use 10k resistors not 4.7M. (Assuming the Vs = 12 Volt)

My recollection is that switch contacts need at least 5 Volt across them when open & at least 1 mA through them when closed. This prevents problems with contact oxidation. The voltage breaks down any oxide film and the current presumably increases the area of contact.

can u please give me this lock theory in detail ....

I have seen simular locking systems before. It is a good design, but like mentioned before, there is a portion of the lock missing. And I can see one flaw that would render the lock unable to function, under the right condition. First I'd look at changing the relay to a DPDT, this will be apparent why in next few sentences. I would add a 555 "one-shot", set for a couple of seconds. I'd tie its output into the reset portion of your 4013's. And to trigger the "one-shot" would be the second pair of contacts from the relay. When they close they should start the timer and thus resetting the lock system. Oh, and the flaw I notice, its the LED in circuit with the relay. If this were to burn out, and it looks like it would (no current limiting resistor), then the relay would not be able to complete its circuit. I'd parallel the LED and use about a 330ohm ¼w 5% resistor and take the relay strait to ground.

that is D flip flop...