alarm clock for cars - for sleepy drivers

. for sleepy drivers radio can be switched on and off via a relay contact. Switch on the supply; the display should then flash. Setting the time: ensure that switches S1 . . . S8 are open. The time can then be set with S6 (fast) and S7 (low). Setting the alarm: set as time but with S5 closed in addition. Make sure that the switches are opened again after setting, and remember a.m. and p.m. Setting sleep time: close S3 when the display will read 00:59. This time may be shortened by pressing S6 and/or S7. As long as S3 is closed, The circuit is based on the MM 5387A, a relatively new (though readily available) IC which drives LED displays directly. For use in a car, a quartz controlled time base is provided around IC2/1C3. The crystal frequency of 3.2768 MHz is divided to a final clock frequency of 50 Hz. If mains 71 operation is used, this part of the cir- cuit may be omitted and the mains frequency used as clock (the mains 01.1: 2 : 1 must, of course, be isolated from the circuit ...