Voltage-controlled timer PUBLIC

Apply a frequency control voltage (labeled "fan power") to a 555 timer. Designed to emulate a the output of a DC controlled fan with a rotation encoder.

Fan speed is sometimes controlled in closed loop feedback. However, when the fan is not physically connected this may cause certain electronic devices to shut down, even if they are cooled by other means. This circuit was designed for an Acer K11 projector for which we provided separate cooling. R3 controls the charging rate of C1 - charged by a current of "fan_power"/R3. Generated waveforms are asymmetric.