I am trying to build a circuit that turns on an LED about every hour for 1 minute, and started by building a 555 timer circuit (according to http://www.csgnetwork.com/ne555timer2calc.html) with calculated R1 at 540000 ohms and R2 at 9000 ohms. I have the capacitance at 9400 uF by two 4700 uF capacitors in parallel. When I tried using this however, the led never turned on. I then tried changing the values to make high time two minutes and low time one minute, which worked fine. I also tried 10 minutes and one minute, which caused the led to turn on first after fifteen minutes and on for seven seconds and then continue turning on every four minutes. Is the 555 timer inaccurate or could I be doing something wrong? Should I be using other methods to construct this timer? Any advice would be greatly appreciated.
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