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An enhanced five alarm keypad circuit

2016-02-21 11:22  
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This article describes an enhancement of the 5 alarm keypad circuit. This circuit is not new, but it proved so useful, simple and cheap, it is worth building. This switch will be suitable for modular burglar alarm circuits. However, it also has other applications. Keypad must be of the kind common terminal and a separate connection for each key. In a 12-key pad, look for 13 terminals. Matrix type with 7 terminals will not do. Select your desired five elements as your code, and connect them to the "A, B, C, D and E". Line common to R1 and all the remaining keys F. Because your choice can contain non-numeric symbols, almost 100 000 different codes are available. Alarm is set using the first four of your five selection key. When the "A, B, C and D of the pressure in the correct order and for a time set in C1 and R2 (about 10 seconds), the current through the switch to R11 progress of this relay is excited, and then by its own base current through R12 schedule 12 volt output switch from "off" to "Settings" terminal, and LED lights. off at the alarm time and necessary A, B, C, D and E in the correct order. IC is a four 2-input AND door, a Cmos 4081. these gates generate a high output only when both inputs are high. Press "" In a time setting pin 1 is high, C1 and R2. this "so that" the door 1, so that when "B" Pressure output at pin 3 will be high and this output and two jobs and it locks itself high using it so that the door 2 R3 and to pin 5 high. remaining gates operate in different ways, each lock itself through a resistor, so his successor. If you enter the correct code is in the time allowed, the pin 10 will switch Q6 Q5 in so connected to the ground base, which led to Q6 off and relay drop out. any key is not connected to "A, B, C, D and E "is connected to the base by the R9 fourth quarter. Whenever these" error "key is pressed, the fourth quarter off a low need, which eliminates the" Enable "from the door 1, code entry process fails if C, D and E in order of precedence, Q1, Q2 and Q3 will be off a low, same result. You can modify the code by changing the keyboard connector. enter a password if you make a mistake, just start again if you need a more secure code, you can use a larger keyboard and more "wrong" key to connect to F. a 16-key pad to more than one million different codes. displays all the components lie flat on the board, but some are actually installed Upright This link is a bare copper wire assembly side. both links must be installed in the integrated circuit of the circuit is very simple, we want to help you.(1N4148 )
 

Alarm Keypad

 

Veroboard Layout

vero layout

 

 

 


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