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An Alarm Control Keypad Circuit

2015-03-03 21:27  
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IC is a quad 2-input AND gate, CMOS 4081 . The alarm will turn off when the four linkage "A, B, C, D" is to promote the correct order. Circuit works because each door "station" in its predecessor. If any other key than the correct key is pushed, then gate 1 is knocked out of the stack and code entry fails. Pin 1 is to have a higher R4. When both inputs are high, the gate produces a high output only. When the key is connected to the "E" voltage, the current through R1 and D1 switches Q5. This relay energises; and Q5 is "concerned" R8. This "so that the" Gate 1; And when the button is pressed, 'A', the output at pin 3 will be higher. This output and tw1o work. It locks itself "through the" make "R2 and the door 2 to pin 5, high-Now, if you press" B ", the output of gate 2, the pin 4 will rise. Tw1o this output and work it through the lock itself and it makes the "R3 door 3 by a pin 12 is high. Now, if you press "C", the output of gate 3 will lock itself "in" in order to pin 8 through R5 high "so that the" door 4. Pressing the 'D' cause the door to 4 do the same thing, only this time it's output, the pin 10 in the fourth quarter. "It needed basis. Q5 to the ground, it shut down, so that the relay dropout this switch alarm makers. any key is not connected to the "a BCDE" which is connected to the base Q1. When "E" or the other key is pressed, the pin 1 is taken low and the circuit is reset, if anything other than "B" key is pressed , the circuit will be reset. Similarly, "B", if any key in addition to the "C", this circuit will reset The same logic applies to "D". keyboards require the kind of common terminal and a separate connected to each key in a 12-key pad, looking for the terminal 13. matrix type with seven terminals will not do. line common code of your choice R1 and 'BCD'. Line "E" key you want to use the alarm switch All the rest went to the first quarterly basis. This chart should give you a rough layout of the components, if you are using a board code of your choice can include non-numeric symbols. 27 k resistor can be replaced by a value of up to 100 k. The only requirement for 4 k7 resistors, they provide sufficient protection to connect the current of the transistor is completely right. capacitors (C1 and C2 C3 C4 C5) has a slow response time and overcome any contact bounce, they may be unnecessary .

image001 alarm control keypad