audio-talk

And to answer Simons point, I too have thought of doing something similar to get a LED to flash at 50Hz. I do have one of these somewhere (actually I know where it is, its got a MEMS's device connected to it via i2c as I was playing at making a electronic turntable level).

https://www.mattairtech.com/index.php/mt-db-x4.html

But anything that you could attach a 16Mhz xtal and one or more LED's to would do the job. 50Hz from 16MHz is simple as anything, but not much more code to get it switchable to 50/60/300Hz using DDS. Its how I synthesize the sine wave for the turntable controller.

Hi Nick,
Thankyou for that, I did see something on another site, it is made up of 3 x LED,s 1 x 2n2222, and a couple of resistors. Unfortunately, I am not sure where to connect it to to get the correct flashing rate to give you a good steady square. I tried the neons and they just dont get bright enough. I will try you suggestion, I think I have the bits at home. Will show photos if if work good.
Regards

to give you a good steady square

I should have a play with it, I am not sure square wave is optimal. I think a shorter on time as long as it provides enough light is better as it should give cleaner edges to the strobe marks.