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.
The 78XX series voltage regulator integrated circuits do not support an input voltage greater than...
This is the complete circuit of a multimeter using a 50 uA instrument with a 2k coil. The circuit...
This circuit came out in a Popular Electronics from December 1995. It is a double T configuration that...