I have a 555 timer connected to an LED that I am trying to strobe for 450ms on, 72ms off to replicate an existing strobe light I have. The issue I am having is it is strobing at around 243ms on, 42ms off. According to my calculations, in order to get that timing I would need
Ra=37.2k, rb=6.2k, with C=9.3uF. My actual values are
Ra=56K, Rb=10K and C=9.3uF, however. According to the formulas found online for
Tl, with those values, I should be getting 460ms on and 69ms off, which is close enough for me. I am reading the pulse durations with a light sensor connected to an arduino running on a separate power supply. I've tried replacing the 555 timer with a different one (I bought 5) and it doesn't change anything so I'm really not sure what is happening to make it run the way it is. Is there something wrong with my circuit or am I missing something here?
Edit: the capacitor is a 106 ceramic, which should be 10uF but I measure it at 9.3uF