A,
Combination has been widely used in our daily life, the input password is correct, the lock open; Password input mistake too many, will trigger the alarm,
Second, design task and requirements
There are 9 (1) button, 1, 2... 9,
(2) using light-emitting diodes (leds) as the output light, the password is correct, the green light; Password mistake, red light,
(3) the record number of errors,
(4) the password input error count to three, a sound alarm,
Three, the optional equipment
(1) dc regulated power supply,
(2) integrated circuit: CC4017 NE555, 9013805 0, IN4148,
(3) keyboard, resistance capacity components, leds,