Based on Radio Shack 276-137, this circuit was found in the December 1995 issue of Electronics Now magazine. The circuit drives an LED but could use a relay instead.
This circuit activates a machine to dry hands (fan and heater) when the sensor detects the...
The operational used is like the 741. The circuit is from the datasheet and the formula that...
The second order filter shown in the figure is suggested by Texas Instruments, based on the TL081...