Free circuit schematics - wiparat.com

Senses high current-flow into power cables
No wire-cutting, three versions available
The basic circuit is shown top left in the drawing and must be used in all three versions. IC1 acts as a differential amplifier having a gain of 220. The small AC voltage picked-up by L1 is therefore amplified to a value capable of driving the [...]

Detects the amount of salt contained in liquid foods
Three-level LED indicator
This circuit was designed to detect the approximate percentage of salt contained in a liquid. After careful setting it can be useful to persons needing a quick, rough indication of the salt content in liquid foods for diet purposes etc.
IC1A op-amp is wired as a [...]

This circuit is used to trigger a camera’s electronic shutter circuit when a flash of lightning is present. This circuit would also work for photographing fireworks displays or other events involving flashes of light. [....]
Read more