Electronic Lockers

Posted on Feb 4, 2014

This circuit is an Electronic Locker. It is controlled by a switches combination (by a code). There is a switch matrix on the door of the locker. This one is a unit of switches connected into 4 arranged of 4 columns for a total of eight terminals. When we press on a switch, this one establishes the contact between its column and its line. This swi

Electronic Lockers
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tch matrix is also used in the telephones, for example. But it is numbered from 0 to 9 and from A to F for a total of 16 switches. To open the locker, we have to press 4 specific and different switches in the good order. If for example the code is 0, 1, 2, 3 and we press two times to the same switches: 0, 1, 2, 2, 3 the locker won`t open. In this circuit, the code is 0, 1, 2, 3 but we can set the desired code when we built de circuit. The desired line (called "stage" in the schematic) is connected to the ground and to a pin of the 3. 3k resistor and the other line is connected to an input of the 7408 and to the other pin of the resistor. All the desired numbers of the code are in the same line. To set the order of the number of the code, we have to set the good connection between the node of the 7414 input and the appropriate node of the capacitor. For example, if we select the first line (y1) and the code is 0, 1, 2, 3 the first number (#1) is connected to the top left contact (x1). The switch 0 is corresponding to x1/y1. These points of contact are colored in orange in the schematic. When the locker is locked, the red LED is turned on and the green LED is turned off. When the locker is opened, the red LED is turned off and the green LED is turned on. To lock the locker, we can push any of the 16 switches of the matrix. The locker is powered by a 6V source. I recommend using a 6V rechargeable battery because this one lasts...

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