Simple circuit times bathroom fan


Posted on Apr 15, 2012

Forget to turn off the ceiling fan in your bathroom? Install the simple timer in Figure 1. It`s located out-of-sight in the fan unit, and you turn it on via the wall switch. The circuit costs virtually nothing, using `junk` parts. When ac power appears, a simple rectifier develops approximately 7V across filter capacitor C. This voltage powers the LM2905 analog timer and simultaneously triggers it via trigger-input Pin 1; output Pin 7 then goes low, turning on the solid-state relay and fan.






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