I need to a clock pulse where each pulse last 5 seconds for a traffic light controlling system assignment. I haven't worked with the 555 timer much and I haven't had any success with this. I used the equation t = 0.7*(R1 + 2R2)*C and tried designing a circuit with a 470uF cap, 1K r1 and 7K R2, but this only gives me a signal of around 4 seconds. Why is this? And how could I fix this?
555 timer – Creating a 5 second astable pulse
555astablepulse
Best Answer
There are at least three things that can affect this:
If you are within spitting distance of the timing you need, slightly adjust the capacitor or resistors until you get where you need to be. Easiest would be to perhaps use a potentiometer to make those adjustments.
And I agree with everyone else: In real life, it's easier to use a microcontroller with built-in timers and oscillators. An AVR ATTiny85 would need zero support components to do this (although a de-coupling capacitor would be good form.) Too bad you can't use it :-)