Electronic and electrical testers circuit diagrams electronics projects

Using the LTC1042 chip, manufactured by Linear Technology, can be designed a TTL signals monitor circuit. LTC1042 is a window comparator that can work with some very small currents.

A low battery indicator can be designed using this electronic scheme.
Current through circuit not greater than 1 mA and therefore it is not an additional big task for the battery.

This simple battery state tester which can simply check state of charge of the different types of batteries.