Post AW3iAR6eu46VtP3MLw by hanshuebner@mastodon.social
 (DIR) More posts by hanshuebner@mastodon.social
 (DIR) Post #AW3iAR6eu46VtP3MLw by hanshuebner@mastodon.social
       2023-05-26T20:51:15Z
       
       1 likes, 0 repeats
       
       #retrocomputing activity today:The fans in the cisco 2811 router were way too loud and I exchanged them for modern silent ones.  These spin slower than the original fans, which caused IOS to complain with three warning lines every 30 seconds:Jan  2 12:00:30.119: %ENVMON-4-FAN_LOW_RPM: Fan 1 service recommended I found https://www.techidiots.net/notes/fake-fan-sensor, a simple circuit based on a 555, a resistor and a capacitor. Now the router is pleasantly silent. One 555 can drive all 3 fan tach inputs.