This circuit was found in a Popular Electronics from the 90's. The CMOS integrated circuit used is not very common nowadays. The range depends on the infrared LEDs. R7 can be changed.
This circuit works both as a preamplifier and activates a relay when speaking in front of the...
This simple CMOS touch switch with bistable action must not be powered by a source without a...
This circuit activates an incandescent lamp (it cannot be of another type) when it gets dark. The...