Logic Probe

This Logic Probe is a low cost circuit analysis and troubleshooting tool for digital circuits like; microprocessor, and microcontroller circuits. The Seven Segment LED (Light Emitting Diode) display will visually show the binary state ("H" for Hi) and ("L" for Low) of the target digital, microcontroller, and microprocessor circuit under test or analysis. 

When the voltage is 2v or less than 2v it will indicate L. And high range is from 3v to source supply.

Schematic:

Components Required:

R1-R2,   1kΩ  Resistor
RP1,       330Ω Resistor Bank
DS1,       Seven Segment CA
IC1,        74ls04
B1,          5v Battery (Error in schematic voltage)