What’s been your most interesting implementation of a 555 timer?
Remember the piezo contest GHI sponsored awhile back? I initially attempted to do it with two 555s. It mostly worked, but since it was a hardware solution, was impossible (for me) to tweak tones to sound decent. The experience was extremely educational, however.
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That is sad news. I remembered we had to explain all the inner details of the 555 back at school. Its a very clever IC.
I still want to see that peizo with 555 timer 
Why couldn’t you add a few resistors/capacitors that you can control from different IOs to make diffident tones? You will be limited to 5 tones for example but at least you can make different tones.
I was able to get plenty of audible tones, and even play a hacky sounding star wars theme, but some of the “notes” had odd harmonics that made them sound crappy with clicks and other odd noise effects. The circuit was 90% there, but it had to be 99% for the contest
In doing the homework on 555s, I was amazed to find how many different hardware applications they have.