This is a liquid level sensor circuit that sounds off an alarm when a liquid has reached a certain level. It can be easily constructed using a single IC L4620 and few external components and has an oscillating freq. of 1.6 kHz.

The over temperature sensor circuit described here keeps a constant watch on the temperature level and gives an indication when the temperature level goes above a certain value. The temperaturse sensor circuit is simple and uses a CMOS IC CD4060(IC1). A standard PTC type thermistor works as the heat sensor.

This improved infrared detector is specifically intended for use with commercial IR remote control handsets. This little circuit is useful for quick go/no-go testing of just about any remote control transmitting Infrared (IR) light signal.

This Simple Voltage and Current tester can be used to measure the forward Voltage drop and current through Semiconductor Diodes like LED, Infrared diode, Photo diodes, Silicon diodes etc. This is ideal to assess the voltage and current drops through these devices during circuit design and calculating the power consumption in a particular section of the circuit.