Friday, August 23, 2013

Timer for Sleepy Eyes

Here my search result of IC 555 application that very close to what I want; the Pivot Headlight Retractor like Sleepy Eyes on my Mazda 323F Astina
the 555 timer is set to turn on the buzzer when the push switch is pressed; the buzzer sounds for approximately 8 seconds. This is a monostable circuit as it works only once. The switch must be pressed again for the buzzer to sound again.

Well, almost there, but I do need more...
 It have to
  • turn on when the headlight goes off after on
  • turn off after certain seconds (more or less half second)
  • reset timer when headlight goes on
The schematic above didn't meet the requirement as the push button act as trigger while my 'trigger' is the headlight off condition. So if it applied directly, the timer will run continuosly since the trigger is always on and the 'reset' is above 0.7 V.

So, here is my mod

oops, what's wrong? oh, it's like pin 4 must go to Batt, not headlight, :)