I am trying to build a long duration timer as part of a bigger project. I found one at
QKits Electronic Kits with their model QK152. A bit surprised (but should not have been as it was a "KIT", when it came and it was in pieces! I put it together and it does everything I want it to do but the max time delay is 8192 seconds or about 22 hours. It says the values for R1 and C1 can be changed to make longer times but they have no chart. I need the timer to count to 690,000 seconds or about 8 days +/- 10%.
They say you can put two kits together to get up to 20 years but it will make my overall project to expensive.
Can anyone recommend values for R1 and C1 that would be compatable with the 555 chip?
Thanks for any help, Doug