# Astable 555 Timer creates longer pulse when just turned on

I have a question regarding the behavior of a 555 timer circuit that I have made. It is depicted below.

Now, here is some interesting behavior, I wrote a program on arduino that measures the lengths of the pulses from this 555 timer. Here is the output that I had.

  Was on for: 472
Was on for: 279
Was on for: 279
Was on for: 277
Was on for: 278
Was on for: 278
Was on for: 278
Was on for: 279
Was on for: 277
Was on for: 278
Was on for: 278
Was on for: 277


Now, as you can see, when the 555 timer is first turned on, the pulse is much longer (measured in milliseconds). My question is, how would I avoid this behavior? In other words, how can I turn an astable 555 timer on and off and have the first pulse be the same length as all of the other ones?

• Does anyone else feel that on calculation last pulse deviates just too much from actual answer that is around 303ms. And value of control capacitor is too high. Jan 1 '16 at 8:09
• @manav.tix, that last pulse is an anomaly because I turned off the circuit, I will remove from the question since it is confusing. Jan 1 '16 at 8:10
• I tried the solution with .47,0.047 uf caps and it does Not work... am i missing something or simply it does not work... Jan 23 at 2:04
• @Bulent If you have a question please ask it as a new question. Note that the added cap should be 50% of the size of the timing cap used. Your is 10% - which will make some difference, but not enough for the purpose. Jan 23 at 3:16