Hello everybody. I am new to this forum, (and to electronics). I am struggling to come up with a strobe for a model airliner: wing tips and red top and belly.
Found a calculator that gave me this formula with the 555: R1 22K ohm
R2 1K OHM, C 100 uf, T1 off 1663 millisec, T2 flash 138 millisec, Hz 0.000554,
I am trying to get the flash every second and a half or so, but I get the opposite effect: the led stays on for 1.5 sec, then a brief off.
What I am missing. Can somebody point me in the right direction? Thanks.

 

Try turning the LED around and connecting it to the other power supply lead (+). This will invert the flash signal.

Have you seen these?

3. The 555 Projects

They show how you can do this.

 

This is what Bill was suggesting. The flash time is controlled by R2 & C, idle time by R1+R2 & C.

 

Thanks for the answer. Such a simple fix.
I have a strobe!