Re: Three Fives 555 behavior

Windell Oskay

The values on the example circuit were picked for being easy values to find, rather than for uniformity of the output signal. 

Plugging the values (100 k, 100 k, 1 uF) into a 555 calculator gives times of:
.14 seconds high
.07 seconds low
4.8 Hz overall frequency.
So, look carefully at your LED blinking, and see if it looks like that. If it doesn’t, first check your *external* circuit very carefully.  It’s pretty hard to get the 555 itself to oscillate repeatedly if there is a major error inside, so it’s more likely that the problem is outside.  Next, go through the 555 and check that resistor values are in the right places, and that the soldering is all secure.