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Explain the principle of programmable digital code lock

2015-01-15 00:46  
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This article is to explain the principles of programmable digital code lock. The combination of text read schematics would be more effective to grasp this principle. The circuit uses two types of dial switches. By TWS8 change numbers TWS1 decimal, bcd converter type switch digital TWS9 through TWS16 are 10 types of input multiplexer, only one input 10 can be connected to the output (pole). Thumbwheel each is used to combine two types of IC CD4028B  (BCD decimal decoder) provides a digital output. Eight so that the same combination switch, IC CD4028 trackwheel use. Eight digital outputs get these combinations are connected to the input of the 8-input NAND gate CD4068. Access logic high output, that in a very 1, it is necessary, by selecting the switch to decimal TWS1 and TWS9 are the same, since only a logic high output at a specific output pin of IC1 will be transferred to the pole 1. Therefore, when the dial on the switch in each combination were matched, the output pole rod 1 to 8 will be logic high. This causes the output of the 8-input NAND gate IC CD4068b is changed from a logic high to a logic level, thus providing a low clock pulse to the clock input pin 7 stage counter CD4024B, used here as a flip-flop (only Q0 output used here). Output (Q0) of the flip-flop is connected to a relay driving circuit of transistors T1 and T2. Torch relay will operate when Q0 output trigger is low. Therefore, to get off the transistors T1 and T2 are forward biased to operate the relay. Switch S1 is provided to enable disconnected (lock) and a switch (unlock) the relay as you would expect, once the correct code has been set. And code correctly set, the output of NAND gate will remain low, the trigger can be connected to any number of times, it can turn on or off the relay, as expected. Suppose we are using the system to switch the power on deck is sent through the relay contacts. People will choose the correct authorization code will cause the supply available to the deck. He will operate after using switches S1, then wash TWS1 Thumbwheel switch through TWS8 this does not generate the correct code. Once the codes do not match, the pressure switch S1 does not affect the output of flip-flop. By TWS16 TWS9 hidden switch to set the desired code. In place TWS1 Thumbwheel through TWS8 DIP switch can also be used. If you are the first to understand this principle, we might Duokanjibian. The principle is simple but effective.
 

Programmable Digital Code Lock

Programmable Digital Code Lock

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