Keyboard switch 4 digit Description This is a universal version of the alarm with four digit key. I modified the design of the outlet section - to free relay contacts.This allows the circuit to operate as a general-purpose switch. I used a relay SPCO / SPDT - but you can use a multi-pole relay if it suits your application. ImportantDo not use the relay "on board" to switch the mains voltage. The layout of the card does not provide adequate insulation between the relay contacts and low voltage components. If you want to switch the mains voltage - ride a proper gauge relay in a safe place - away from the card. Diagram:
Notes:
The relay is activated by pressing a button. Select the key you want to use - and connect to the terminal "E". Choose the four keys you want to use to cut the supply of the relay - and relate them to "ABC & D". Wire the common to all other keys "F" and R1. The circuit is easy to use. When you press "E" - current through D2 and R9 turns on Q6 - and energizes the relay. The two transistors Q5 and Q6 - - form a "complementary Latch" So -. When you release the button - the relay is on. To remove relay power - you must press the keys "ABC & D" in the good order When you do. - pin 10 of the integrated circuit goes high - and it turns out to R8 Q4 Q4 connects the base of Q6 to ground This unlocks the complementary pair -.. and the relay drops. All not wired key for "ABCD and E" are connected to the base of Q3 by R7 Every time one of these keys "Wrong" is pressed. - Q3 takes pin 1 low and the code entry sequence fails. If "C" or "D" is pressed out of sequence - Q1 or Q2 will also take pin 1 low -. with the same result if you make a mistake while entering the code - just start again. The keyboard should be the genre with a common terminal and a separate connection for each button on a block of 12 keys -. look for 13 terminals The matrix type with 7 or 8 terminals DOES NOT WORK.. With a 12-key pad - more than 10 000 different codes are available. If you need a more secure code - use a larger keyboard with more keys "bad" wired "F". A 16-key pad gives more than 40,000 different codes. Support material for the circuit includes a step-by-step guide to building the circuit board, a parts list, a detailed description of the circuit and more .
Notes:
The relay is activated by pressing a button. Select the key you want to use - and connect to the terminal "E". Choose the four keys you want to use to cut the supply of the relay - and relate them to "ABC & D". Wire the common to all other keys "F" and R1. The circuit is easy to use. When you press "E" - current through D2 and R9 turns on Q6 - and energizes the relay. The two transistors Q5 and Q6 - - form a "complementary Latch" So -. When you release the button - the relay is on. To remove relay power - you must press the keys "ABC & D" in the good order When you do. - pin 10 of the integrated circuit goes high - and it turns out to R8 Q4 Q4 connects the base of Q6 to ground This unlocks the complementary pair -.. and the relay drops. All not wired key for "ABCD and E" are connected to the base of Q3 by R7 Every time one of these keys "Wrong" is pressed. - Q3 takes pin 1 low and the code entry sequence fails. If "C" or "D" is pressed out of sequence - Q1 or Q2 will also take pin 1 low -. with the same result if you make a mistake while entering the code - just start again. The keyboard should be the genre with a common terminal and a separate connection for each button on a block of 12 keys -. look for 13 terminals The matrix type with 7 or 8 terminals DOES NOT WORK.. With a 12-key pad - more than 10 000 different codes are available. If you need a more secure code - use a larger keyboard with more keys "bad" wired "F". A 16-key pad gives more than 40,000 different codes. Support material for the circuit includes a step-by-step guide to building the circuit board, a parts list, a detailed description of the circuit and more .