1Hz Clock Generator Circuit Using COB

Let's familiarize with a COB - chip on board device by building a precision 1Hz clock generator. Circuits that usually generate 1Hz clock makes use of ICs with variable capacitors but they are not very precise. ( micro controller based one should be precise but it costs large ). better accuracy can be obtained by a COB found inside a digital clock, which is cheaply available in the market.

Visitor Alarm Secret Bell

This circuit can acts as a visitors alarm as well as a secret bell which can be used to identify family members. If you'e living in flats, it'll become necessary to verify the visitor before opening the door. This circuit senses single puff of breath and activates a musical bell automatically.

LED Running Display Using NE555

Here's a circuit to build a led based running display using easily available general purpose timer IC NE555 and a popular decade counter IC CD4017. This display consist of 24 LED's of four layers. The NE555 is wired as an astable multivibrator whose output triggers CD4017 counter.

Dual power supply from single battery supply

Dual power supply is a very essential part in the laboratory or in your work while there you use op-amps in your circuit. Most of the opamp Ic's require dual voltage supply. But it's difficult to provide dual power supply as it's costlier than a single battery. 

CCFL Tester Circuit For LCD Screens

Lcd's cover a wide range of applications including led tv's to cmputer monitors, PDAs, digital monitors and much more. LCD backlight mainly consists of a light source, diaphragm, light leading board and a plastic frame.  Cold-cathode fluorescent lamps (CCFLs) have a phosphor coated glass cylinder with cathodes at each end. The CCFL inverter accepts a low-level DC input voltage and provides a high-level AC output to run the backlight CCFL tube. Here's a CCFL tester circuit that often needed to check a faulty LCD backlight circuit for finding the dead components.

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Low Cost Hearing Aid Circuit

This can also be called a poor man's hearing aid because it can be constructed from some low cost components although its performance is not comparable to that of commercially available sophisticated hearing aids, still it can serve the purpose well for persons with a low degree of hearing impairment.

Circuit Diagram Of Low cost hearing aid

This circuit utilizes two Sanyo’s MSI (medium- scale-integrated) surface-mount 10-pin DIL IC LA4537M
which have been cascaded to improve gain and sensitivity in most audible range. With 3V supply voltage, you can afford to use 1/8-watt resistors, while the electrolytic capacitors’ voltage rating can be as low as 5V. This will allow the assembled circuit to occupy very little space. Apart from the usual battery ‘on’/‘off’ switch S1, muting ‘on’/‘off’ switch S2 has also been provided. Both S1 and S2 could be PCB-mount slide switches.